Hatchery Feed & Management Vol 11 Issue 4 2023 by Aquafeed Media

Vol Vol11 10 9 Issue 1 4 2021 2023 2022

NEW SPECIES: RED CUSK EEL New wet multi-layer micro diet Shrimp disease management Water filtration Published by Aquafeed Media S.L.U. www.hatcheryFM.com info@hatcheryFM.com

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VOL 11 ISSUE 4 2023

Contents 4

Interview with Piero Magnolfi Orsini *Cover photo

News Review

12 One step away from closing the life cycle of European eel (Anguilla anguilla) in aquaculture

16 The current state of tropical sea cucumber aquaculture: Hatcheries as looking back and beyond

20 Wet multi-layer microdiet for easier weaning of marine fish Helping hatcheries overcome Transparent Postlarva Disease: 23 HACCP plans and high-quality biosecure feeds What is the best method for early warning 27 and prevention of WSSV in shrimp farming? What role does the health of shrimp post larvae 31 (PLs) play in farm outcome?

We are grateful to the following companies for sponsoring this issue of the magazine. Their support allows us to make our publications available without charge.

BioMar.......................................................................11

36 Unlocking aquaculture success: Gut microbiota management for optimal health and productivity fish welfare at the hatchery through water quality 40 Improving

Reed Mariculture....................................................15

43 Drum filters: The key component for ensuring clean water

Hatchery Feed & Management..........................19

Harvest Rake helps fish hatchery maintain optimal 45

FishFarmFeeder.......................................................19 Socorex.....................................................................22 Zeigler........................................................................26

conditions for trout farming

48 Calendar of events

Tianjin Ranova.........................................................35 AquaFarm................................................................49 World Aquaculture Society...................................50

HATCHERY FEED & MANAGEMENT

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Hatchery Feed & Management Vol 11 Issue 4 2023

HATCHERY FEED & MANAGEMENT

VOL 11 ISSUE 4 2023

Contents

METHODS FOR EARLY WARNING AND PREVENTION OF WSSV IN SHRIMP FARMING 27 A CSIRO’s study assessed the effectiveness of shrimp point-of-care test kits in controlling WSSV and found a lack of sensitivity that creates a false sense of security for farmers.

CLOSING THE CYCLE OF EUROPEAN EEL 12

A BIOMIMETIC APPROACH FOR EASIER WEANING 20

IMPROVING WELFARE THROUGH WATER QUALITY 40

A group of researchers is working to develop the technology that will allow the production of glass eels in aquaculture.

A wet micro diet produced through a multilayer encapsulation technology for an easier transition from live feeds to dry inert feed.

The relatively low water flows in hatchery systems make them uniquely suited to finer filtration.

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INTERVIEW with Piero Magnolfi Orsini Piero Magnolfi Orsini is Founder & General Manager of Colorado Chile HFM: Colorado Chile is the only company in the world that cultivates red cusk eel. Where did the idea to raise this species come from? PMO: The idea originated in 2006 and is a family initiative linked to the Magnolfi family – my father, a civil construction engineer, my brother, an environmental biologist, and myself, a marine biologist. In my early professional encounters, I saw red cusk eel broodstock (Genypterus chilensis) at the Quintay Marine Research Center of Andrés Bello University in Chile, and my father saw a business opportunity. At that time, 3,000 tons of red cusk eel were extracted in Chile, and today, only 400 tons are extracted due to overfishing. Additionally, red cusk eel is a well-known species in the country, so introducing it to the market wouldn’t require much marketing effort.

During the first six years, we started with private capital and our own investment. As we began to see technical results, Corfo, a state entity supporting research and development in various areas, started supporting the initiative. We moved to the Coquimbo region with a raceway and low-column tank farming system. During the first two years, we focused on capturing wild broodstock, diving to understand the red cusk eel’s habitat, and evaluating stomach content to identify prey and seasonal feeding patterns. Red cusk eel is a gregarious species until maturity when they become solitary. This behavior has allowed their production in tanks with a low water column. In 2021, in collaboration with Aquamiks, we optimized the farming system, production, and juvenile quality.

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Colorado Chile’s 20-ton red cusk eel farm

Red cusk eel is raised at high densities

HFM: What are the main challenges in managing broodstock? PMO: Red cusk eel is a species with many continuous spawnings – a female can spawn for 120 consecutive days. The main difficulty was identifying viable and high-quality eggs. Currently, spawning is controlled through a photothermal period, and is standardized so we have spawns throughout the year. Broodstock are individually identified in tanks in pairs. We use in vitro fertilization, and genetic control is done through sperm cryopreservation. We have obtained F1 broodstock and are working to obtain F2. Moreover, in collaboration with the University of Chile, we are genetically selecting families with different characteristics such as rapid growth, disease resistance, early maturation, etc. At the same time, we have studied natural red cusk eel populations in Chile to determine if they are part of a large unique family. We have found genetic differences between populations in the southern, central, and northern regions, likely due to different environmental conditions. We conducted this study because part of the

company’s plan is repopulation, and we have identified broodstock for each zone.

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HFM: Regarding the larval stages, what have been the main difficulties, and what is the current survival rate? PMO: In Chile, there is no commercial marine aquaculture industry, so there is a shortage of qualified personnel. We have had to train our staff and during those years when we had larval survivals of 15-20%. Thanks to the consulting services of AquaMiks, we have increased it to 30-35%. In addition to survival, we have shortened the larval phase from 90 days to 60 days. The same has happened in the following nursery and grow-out phases, which have been shortened due to improvements in the farming procedures and the improved quality of juveniles. Larvae adapt very quickly to dry feeds, and we complete weaning in 10-15 days. Our larval production is stable throughout the year. With the mentioned assistance, we have reinforced and optimized our protocols and introduced new inputs such as probiotics. Some of these products had not

been commercialized before in Chile or Latin America, opening up a new line of business. HFM: Grow-out is done on land. What are the peculiarities of this species? PMO: Red cusk eel is a gregarious species until maturity when they become solitary. The behavior is like that of an eel and wolffish. We have identified that optimal densities are up to 330-340 kg/m3 at harvest after conducting animal welfare studies in cooperation with Akva-niva. In these studies, we observed that the lower the density, the more stressed the fish become. As a native species, red cusk eel brings resistance to local pathogens, which has helped us avoid using antibiotics throughout the farming cycle, along with appropriate engineering designs. This species also has a high level of mucus on the skin, increasing its protection against diseases. Furthermore, we have been able to enhance this barrier in captivity through special diets. The health management aspect has been developed in collaboration with VEHICE. Our farming system reuses 50% of the water. With the remaining 50%, the idea and project is to install hydroponic systems with species tolerant to seawater or to purify the water since there is a shortage of freshwater for human consumption in Chile. The complete cycle of red cusk eel from hatching to 2 kg takes 32 months. The first 60 days are in the hatchery, 2 months in the nursery, 8 months in pregrow-out with fish from 15 to 60 g, and 18 months for grow-out from 100-120 g to commercial size.

Colorado Chile’s founding and co-founding team. From left to right: Jaime Pérez, founder & director; Juan Pablo Oryan, director; Daniel Mas, co-founder & director; Spartaco Magnolfi Jr., founder; Spartaco Magnolfi Sr., founder & director; Piero Magnolfi, founder.

HFM: Have you developed a special diet for this species? Does it have any special nutritional needs? PMO: Red cusk eel is a lean fish high in protein (20%) and low in fat (7%), distinguishing it from the salmon market and targeting another segment with a profile similar to cod. We manufacture the diet for broodstock, and the rest of the diets are commercial, high in protein, and low in fat. We have collaborated with Cargill for years, and they have developed a specific diet for this species from weaning to grow-out up to 2 kg. Additionally, we are also testing an Aller Aqua diet. HFM: Would it be possible to raise this species in other regions? PMO: The temperature range of red cusk eel is 11-18°C. In certain countries like Spain, known as conger or Pacific pink cusk-eel, it is a well-known species, and there is demand, but due to restrictions on the introduction of non-native species, farming is not possible. In countries where these restrictions do not exist, such as Brazil and Peru, and where it is also a wellknown species, it would be possible to raise this species. HFM: What are the growth projections for the company? PMO: In 2021, Kawen, a business accelerator, joined Colorado Chile as a new partner. At the moment, we are looking for investors to establish a first commercialscale plant. Today, we have a pilot of 20 tons per year, and the goal is a first farm of 500 tons per year and scale it to 1,500 tons. We are the only company in the world that farms this species and are offering a 20% share of Colorado Chile to incorporate a strategic partner from the sector. Additionally, we have an agreement with Orizon, a Chilean fishing company, for the preferential purchase of the first 500 tons and the potential share entry into the company for the scaling of the next 1,500 tons. We are conducting a market study, and we have seen that the demand in the Horeca market ranges from 800-2,000 g, because it is a gourmet category product, free of parasites and for possible consumption in sashimi. At the moment, we are defining what the commercial size will be. Morevoer, we are committed to research and have just signed a research agreement with the University of Ancona, Italy, to develop this and other species.

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NEWS REVIEW

NEWS REVIEW Highlights of recent news from Hatcheryfm.com

Hendrix Genetics opens shrimp breeding multiplication center in India

CAT backs Prima Larvae Bali in advancing whiteleg shrimp breeding Prima Larvae Bali (PLB), a leading hatchery in Eastern Indonesia, is bolstered by the expertise of the Center for Aquaculture Technologies (CAT) to elevate their whiteleg shrimp (vannamei) breeding program. This support enhances PLB’s commitment to delivering biosecure, top-quality post-larvae suited for Indonesia’s unique farming landscape, while also introducing cutting-edge genetic technology. Both organizations aim to refine the selection of genetic lines for shrimp that grow quickly and thrive in commercial settings.

The Indian BMC, located in Ranasthalam Mandal, Srikakulam District in the Andhra Pradesh region, has a broodstock production capacity of 150,000 and is managed by Kona Bay, a subsidiary of Hendrix Genetics, under the local leadership of Deepak Patnaik. The BMC maintains the same genetics as the current imported broodstock from Hawaii, maintaining a Specific Pathogen Free (SPF) status.

CAT and C4U bring CRISPR-Cas3 to aquaculture The Center for Aquaculture Technologies (CAT) partnered with C4U Corporation to apply CRISPR-Cas3 technology to promote genome editing in major commercial fish species and drive technological advancements within the industry. “At CAT, there’s a firm belief that genome editing presents the most feasible and sustainable pathway to meet the world’s increasing food requirements and contribute to the economic vitality of the aquaculture sector,” the center said.

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Spring Genetics management team completes buyout from Benchmark The management buyout (MBO) team led by Hideyoshi Segovia has established a new company, Advanced Aquaculture Biotechnology to execute the MBO and has secured financial backing from solid partners to support further growth and development. Spring Genetics and Benchmark will continue to work together to further develop and enhance the tilapia breeding program.

NEWS REVIEW

I&V Bio, Skretting sign partnership for Artemia enrichment

Pure Salmon Technology acquires Graintec’s feed technology

Leveraging the innovative prowess of I&V Bio and Skretting’s industry expertise, the collaboration aims to redefine the standards of aquaculture nutrition through the application of Skretting’s ORI-N3 to enhance the nutritional value of I&V Bio Group’s Artemia.

Pure Salmon Technology acquired Graintec’s HyFlow™ waterborne feed technology. The HyFlow concept is based on waterborne transport and dosing of fish feed in RAS. Water from the recirculating system is directed to the HyFlow unit, where an accurate amount of feed pellets is dosed into the water flow ensuring precise feeding.

Evonta develops automatic device to test salmon eggs The German-based company was one of the finalists of Aqua Nor Innovation Award with a fully automatic device for non-contact and non-destructive testing of salmon and trout eggs. It is the first commercially available device for fully automatic testing and diagnostics of fish eggs.

INVE Aquaculture celebrates 40 years of innovation and growth INVE Aquaculture, part of Benchmark, celebrates its 40th anniversary. This milestone not only marks a festive moment but also the culmination of four decades of pioneering work that has been at the cradle of the aquaculture industry as we know it today. In line with INVE’s philosophy of operating in close proximity to its customers, the company will celebrate this anniversary by hosting small-scale events throughout the year and across the globe.

BIO-UV Group signs partnership with Innovasea Within this agreement, Innovasea will take BIO-UV Group’s water treatment products to the aquaculture market and adapt the group’s proven products to meet the standards for sale in the North American market.

Hatchery Feed & Management Vol 11 Issue 4 2023

NEWS REVIEW

Luminis unveils app to deliver microbiome insights directly to users

New partnerships for big land-based projects

The microbiome analysis company unveiled the Luminis mobile app, an addition to its AquaGENius service line. By providing real-time data on six key areas of the aquatic microbiome, the app provides insights that enable users to make informed decisions.

Norwegian company receives patent for automatic sex sorting of farmed fish

GreenFox Marine had its patent application for automatic sex sorting of farmed fish approved in Norway. The solution improves conditions for fish at hatcheries and in cages, increasing fish health and productivity. The solution operates with an accuracy of 97% to 99% and will be soon integrated into vaccination machines.

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Pure Salmon Technology announced the continuation of its collaboration with Helgeland Smolt for their upcoming smolt facility in Kilvika, Meløy, Norway. The company will deliver electro and automation solutions, process equipment, and support systems for a new smolt facility of Helgeland Smolt. Bakkafrost signed a contract with Nofitech to build a new smolt hatchery in Skálavík in the Faroe Islands. The new recirculating aquaculture system (RAS) smolt hatchery will have a total capacity of 28,600 m3 and is expected to be up and running in late 2026. AKVA group has partnered with Icelandic salmon farmer Laxey (formerly Icelandic Land Farmed Salmon) for the installation of a RAS smolt facility in Vestmannaeyjar, Iceland. The facility marks a milestone as the first of its kind in Iceland – a true RAS facility, and one of the most advanced hatcheries in the world for salmon smolt.

BIO-UV Group has taken a major step forward in Chile’s booming aquaculture market, supplying its innovative triogen® PPO3 ozone generator to leading global salmon producer Cermaq. Hima Seafood, currently building the world’s largest land-based trout facility, partnered with Sterner to deliver a sludge treatment solution.

NEWS REVIEW

Construction begins on Europe’s first large-scale shrimp RAS

Land-based aquaculture technology specialist, Billund Aquaculture, and Aquapurna, a tech-company focusing on cost-efficient shrimp RAS, have teamed up to build Europe’s first shrimp Recirculating Aquaculture System (RAS) at the Sigmundshall Industrial Site, in Hanover region, Germany. The construction of the inaugural mode is due to start in January 2024 and is specifically designed to work at large scale and high densities.

MSD Animal Health introduces two training modules in its fish welfare series Two new free training modules in its AQUA CARE365™ fish welfare series are available addressing important operational and welfare aspects of Harvest and PIT Tagging. The two new modules are part of a series of six modules in the AQUA CARE365 program, which also includes Farm Fish Behavior, Sea Pen Handling, Anatomy and Vaccination, along with a prerequisite lesson on Fish Welfare.

Partnership to develop predictive services to improve fish welfare and growth

ECOshrimp achieves milestone in its industrial shrimp RAS model

ScaleAQ Software and BiOceanOr signed a cooperation agreement to join forces toward leveraging water quality forecasts to improve fish welfare and growth. The agreement will empower fish farmers to experience unrivaled forecasting capabilities and related recommendations, out of existing digital infrastructure and data available on sites and highlight possible operational improvements.

The company successfully completed and stocked its shrimp RAS industrial model. This state-of-theart commercial prototype includes a cutting-edge 100m3 tank equipped with innovative filtration and life-supporting units. The 8-meter diameter tank is specifically designed for growing shrimp at high densities, boasting a remarkable production capacity of over 15 kg/m3 before harvest.

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NEW SPECIES

One step away from closing the life cycle of European eel (Anguilla anguilla) in aquaculture Dinis Cardoso, Annalena Karyda, Camillo Rosso, Rick Leemans and Dana Nolte, Glasaal Volendam

The research team of Glasaal Volendam. From left to right: Dinis Cardoso, Annalena Karyda, Camillo Rosso, Rick Leemans and Dana Nolte

Life cycle and challenges Closing the life cycle of European eel (Anguilla anguilla) in captivity is crucial for a sustainable future of European eel farming. The current technique to grow wild-caught glass eel into market-size eel is well-established. However, it’s very challenging to develop the technology required to raise glass eel, and it’s even harder to establish a profitable eel hatchery, mainly because the lifecycle of European eel is a complex and lengthy one and still clouded in mystery. The European eel is a catadromous fish species with multiple life stages (Fig. 1). Larvae hatch in the Sargasso Sea, where they develop into leptocephalus larvae. At this stage, they migrate to Europe, crossing the Atlantic Ocean. Just before entering freshwater, they metamorphose into glass eels. After entering fresh (or brackish) water, glass eels become elvers and grow to mature sizes. The individuals return to saltwater as silver eels (still not mature) and migrate to the Sargasso Sea to spawn.

To date, no mature eels have been found in the Sargasso Sea and there is no clear diet described for eel larvae, nor for leptocephalus larvae. It is also unknown how leptocephalus larvae leave the gyre that is the Sargasso Sea. The precise cues and conditions required by eels to mature, as well as by eel larvae to develop into leptocephalus and subsequently to metamorphose into glass eels, are still unknown. The lack of knowledge about the life cycle in the wild makes it challenging to develop protocols for rearing the eel hatchlings in captivity. Current eel farming is dependent on wild glass eels, which are caught off the European coast and then grown into eels for consumption. Some of the glass eels are released back into the water to support the eel stock in inland waters. Nevertheless, the European eel stock is threatened by several factors along the migration routes, such as loss of habitat, pollution, diseases and overfishing. The European eel population has declined by 90% in the past 50 years. Recently, the International Council

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NEW SPECIES

Figure 1. European eel life cycle including the continental and oceanic phases. The completed milestones of Glasaal Volendam can be seen in yellow. The team reached milestone 6 this year and is now one step away from the glass eel stage.

for Marine Research (ICES) reported that the amount of glass eels entering the freshwater from the North Sea is now only a few percent of what it used to be (ICES, 2023). The International Union for the Conservation of Nature listed the European eel as “critically endangered” on the IUCN list (IUCN, 2023). Wild-caught glass eels are a highly sought after product with a high sales value per kg. Glass eels are used for eel farming and in other countries also for direct consumption, but the production of European glass eels has not yet been successful. That is where Glasaal Volendam comes in.

Hatchery technology development At Glasaal Volendam, a group of researchers is working hard to develop the technology that will allow the production of glass eels in aquaculture, in order to reduce the pressure on wild eel populations. Full-grown eels are matured in the research facility through assisted reproduction protocols. This process yields viable eggs and sperm that allow for fertilization to take place. To simulate the natural hormonal changes that trigger the

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eel’s reproductive processes, hormonal administration is applied to allow the development of gonads. The past years’ research was focused on broodstock management and the production of high-quality gametes, which was essential for obtaining high numbers of viable eel embryos. Fertilized eggs are incubated for 48 hours and after hatching, larvae are transferred to their rearing tanks. During the first two weeks, young larvae survive by consuming their yolk sac. When the yolk is almost depleted and the eyes, pectoral fins, mouth and anus of the larvae are fully developed, exogenous feeding starts. This is a crucial moment in the life cycle. In the past two years, the research team of Glasaal Volendam managed to increase the average survival rate of the larvae in the first two weeks from 3.8% to 21.7%, with some batches reaching over 50%. This huge improvement allowed more larvae to enter the exogenous feeding stage and helped speed up the process of developing the right diet and feeding methods that will allow outgrowth to leptocephalus and glass eel.

NEW SPECIES

Figure 2. Hatchery technology development at Glasaal Volendam. Left: Adult broodstock eels. Upper right: European eel embryo inside the egg just before hatching. Lower right: European eel larva just after hatching. The lipid bubble is circular and surrounded by the yolk in a dropletlike shape.

Increasing survival and growth rates for feeding larvae Because of the very specific mouth morphology of eel larvae, feed ingestion has only been observed with the use of a slurry-type diet, which is inspired by protocols for the rearing of Japanese eel (Anguilla japonica) larvae. There are many parameters affecting feeding behavior and consequently growth and survival of the larvae. Some of them include diet composition, feeding regime and particle size. The exact starting moment of feeding is also important. Environmental parameters,

such as water quality, temperature, salinity and light intensity, can also have a big effect on ingestion and survival. The team is running different feeding experiments in order to find out the optimal diet and conditions that will allow eel larvae to reach the leptocephalus, or “willow leaf”, stage and later on, metamorphose into glass eels. The goal is to improve survival and growth rates so that more larvae can reach the glass eel stage in less time. Until last year, the team was struggling with high mortality rates at the bottleneck of 28 days

Figure 3. Growing larvae during one of the feeding experiments. Upper left: Larvae at the beginning of the feeding trial (7.5 mm). Upper middle: Larva at day 42 post hatch (11.2 mm). Lower left: Leptocephalus larva at day 105 post hatch (16.7 mm). Right: Picture of a freeswimming leptocephalus larva.

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EQUIPMENT post-hatching, but after optimizing the ingredients of the diet and adjusting the feeding method, researchers managed to significantly increase survival and growth rates for feeding eel larvae. The focus was to test different nutritional components that will improve the digestibility of the diet. Survival rates increased from 16% to 46% from day 12 until day 42 post-hatch and growth rates improved from 0.12 mm/day to 0.18 mm/ day, which is comparable to the growth rates of captivereared Japanese eel larvae. Improving survival and growth rates was essential to reach the leptocephalus stage in 2023 with several larvae batches reaching more than 150 days of survival. In order to achieve commercial production of glass eels in the future, even higher growth rates are required so that the lengthy larvae stages can become shorter and the production costs can be minimized.

Future prospects for reaching the glass eel stage Next steps for Glasaal Volendam include the standardization of protocols for optimized leptocephalus production. Research will then focus on the induction of metamorphosis into the glass eel stage. At the same time, the team is working on methods and systems that will allow up-scale production in the future. The results that were obtained at Glasaal Volendam over the past year are very promising for closing the life cycle of European eels in captivity. Researchers have managed to develop hatchery production methods, rearing systems, optimized culture conditions and diets that will allow larvae to grow into glass eels in the very near future. This step will be essential for a sustainable aquaculture industry of European eels that will provide farmers with high-quality, all-year-round hatcheryproduced glass eels. This will reduce the pressure on wild-caught eels, allowing the recovery of natural European eel stocks.

More information: Annalena Karyda Aquaculture Researcher Glasaal Volendam E: info@volendamglasaal.com

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NEW SPECIES

The current state of tropical sea cucumber aquaculture: Hatcheries as looking back and beyond Beni Azari, Grisilda Walsalam, Shibu Daniel, Seacucumber Consultancy The global sea cucumber industry faces substantial challenges, primarily driven by overexploitation resulting from surging demand. Traditional consumption in Asia, along with growing nutraceutical and pharmaceutical markets, has led to severe depletion of commercially valuable sea cucumber populations worldwide. Addressing this issue, hatcheries are being recognized as sustainable solutions to ensure consistent, year-round high-quality juvenile production. While temperate sea cucumber hatcheries have been in operation for over 50 years, primarily focusing on cold-water species Stichopus japonicus, tropical and other sea cucumber species are in recent development. Sea cucumber aquaculture has made significant strides, particularly in the diversification of species being farmed. Among five commonly farmed species, Holothuria scabra (Sandfish) holds tropical prominence due to its high market demand and adaptability to various aquaculture conditions. The success and sustainability of sea cucumber production hinge heavily on state-of-the-art, bio-secure sea cucumberspecific hatcheries. These facilities play a critical role in maintaining the health and well-being of sea cucumber larvae and juveniles, optimizing growth conditions, and efficiently managing feeding and nutrition. Seacucumber Consultancy Pty. Ltd (SCC) has achieved significant advancements in tropical sea cucumber hatchery, grow-out, processing, and value-added product technologies. Notably, we have pioneered the establishment of the first commercial sea cucumber hatcheries in Australasia, Asia, and the Middle East. Our environmentally friendly breeding and rearing

Commercially valuable tropical sea cucumber

techniques, for species like sandfish and golden sandfish sea cucumbers, have evolved through extensive research and development funded by the Australian government. These advancements have resulted in successful spawning and larval development, facilitating large-scale breeding, and rearing for commercial-scale aquaculture and restocking initiatives. Currently, with our clean and green technology and design, we can produce millions of sea cucumber juveniles per year that can be used for sea/land farming or sea ranching.

Hatchery technology challenges and advances Challenges faced by sea cucumber hatcheries are multifaceted and complex, primarily the need to replicate

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NEW SPECIES natural environments and life cycles in a controlled setting. Overcoming these challenges is vital for the sustainability and economic viability of sea cucumber aquaculture. Below are some key technological hurdles and our strategies to address them. Broodstock management Maintaining healthy, reproductive broodstock in a hatchery setting is challenging as it necessitates creating natural habitat conditions. Sea cucumbers are particularly sensitive to environmental changes. Our advanced systems, which control water quality, temperature, and lighting, successfully replicate specific environmental cues to support the growth and maturation process in captivity.

Figure 2. Larval stages of sandfish sea cucumber

Figure 3. Larval survival of sandfish and golden sandfish sea cucumber

Figure 1. High value tropical sea cucumber Holothuria scabra (sandfish)

Larval and juvenile rearing The larval development stage is critical and characterized by high mortality rates. Generally, mortality during the first three days post-fertilization can reach up to 40%. Larvae are prone to water quality issues, and their dietary needs are complex. Our developments in optimal larval nutrition and specialized feeds have increased survival rates from hatching to the early juvenile stage to a commendable 15%. Innovations in water filtration and circulation systems have been instrumental in maintaining ideal conditions in rearing tanks. More refined techniques in sterilization, and decontamination resulted in stabilized survival rates after the initial 3 days, underscoring early-stage management effectiveness much critical for overall success.

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Disease management Sea cucumber hatcheries are susceptible to disease outbreaks due to pathogen spread in a confined environment. Our stringent biosecurity measures and quarantine protocols in the hatchery have significantly decreased the risk of disease outbreaks, such as skin ulceration (SKUD) in early juveniles. Enhanced diagnostic tools for early disease detection and improved hygiene protocols are crucial. Research into disease-resistant sea cucumber strains is broadly aimed at addressing these issues.

Figure 4. Sea cucumber juveniles in the nursery tank

NEW SPECIES Juvenile survival and growth Ensuring high survival rates and healthy growth during the juvenile stage (1-10g) is challenging due to the vulnerability of juveniles to environmental stressors. We have improved growth and survival rates with special diets and by optimizing physical and biological conditions, including substrate preferences and density management.

and survival rates. Variability in survival rates at different stages, predation pressures, and the need for space in nurseries are challenges that require carefully planned execution. Additionally, managing these facilities to prevent overstocking, which can cause slowed growth or cessation of growth, is crucial for the success of hatchery programs. Our incremental scaling strategies are designed to identify and resolve issues during the scale-up process.

Figure 5. Grading of sea cucumber juveniles in the hatchery

Figure 7. Sea cucumber juveniles for pre-grow out

Environmental control systems Replicating the natural habitat of sea cucumbers is a technologically demanding task. It involves precise control of water quality, temperature, salinity, and lighting. We are developing advanced systems capable of monitoring and adjusting environmental parameters in real-time.

Solutions and future directions Addressing technical challenges in tropical sea cucumber hatcheries involves several key strategies. To improve larval rearing, it is essential to develop and fine-tune specialized diets and precise microfeeding protocols. Optimization of water quality management systems, including temperature and salinity control, is crucial. The incorporation of automation and real-time monitoring technologies can significantly enhance operational efficiency and precision. Implementing strict biosecurity measures, such as robust quarantine procedures and rigorous disease monitoring, is essential to prevent disease outbreaks. By implementing such solutions, hatcheries can overcome technical challenges and ensure the successful production of juvenile sea cucumbers. The future of tropical sea cucumber hatchery development relies on critical advancements within the hatchery phase. Central to this progress is the utilization of selective breeding and genetic technologies to enhance traits like growth and disease resistance. As climate change continues to impact marine ecosystems, hatcheries will adapt to shifting conditions and develop climate-resilient sea cucumber

Feed development Developing cost-effective, nutritionally complete feeds tailored to sea cucumber life cycle’s unique dietary needs is challenging. Our focus has been on utilizing microalgal concentrates, algal powders, and fermented diets in addition to concentrated live algae cultures. Fermented diets for juveniles are another innovative approach we are exploring, as this allows the incorporation of various organic waste materials, turning them into valuable feed resources. Scale-up and commercialization Most tropical sea cucumber hatcheries are pilot/ small-scale, and scaling these to commercial-scale operations is complex. Challenges include scalability, cost-effectiveness, and maintaining consistent quality

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NEW SPECIES varieties. Optimization of larval rearing techniques, efficient water management systems, and integration of automation and monitoring technology will significantly enhance hatchery efficiency. We are currently investigating AI solutions to boost performance and productivity, while lowering production costs and reducing environmental impact. SCC is dedicated to ensuring sustainability and tackling technical challenges faced by sea cucumber hatcheries. It is crucial to approach the expansion of sea cucumber hatcheries from two distinct angles: bolstering the blue economy and making a positive contribution to marine ecosystems and broader environmental objectives through on-land and or on-sea integrated multitrophic aquaculture (IMTA) in conjunction with other

aquaculture systems and recirculating aquaculture systems (RAS) implementation, thereby promoting both environmental and economic sustainability.

More information: Dr. Beni Azari Principal Consultant Seacucumber Consultancy Pty. Ltd. www.seacucumberconsultancy.com.au

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Hatchery Feed & Management Vol 11 Issue 4 2023

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FEEDS

Wet multi-layer microdiet for easier weaning of marine fish Abdeslam EL HARRAK, Huddle Corp.

What are the needs of the aquaculture industry at the hatchery level in terms of feed? At the stage where fish are most vulnerable, it is very important that every aspect of their environment is precisely managed to limit the risk of mortality, deformities, and exposure to disease. Different feeds and feeding regimes play a role in mitigating these risks, and although the industry is teeming with different products, a catch-all solution has yet to be found. Therefore, hatcheries must combine the use of several products in order to find what works for their own conditions: finding a solution becomes a real art for hatchery managers more or less based on well-described science. However, despite these differences in hatcheries, there seems to be a standard regime that includes the use of live feed with a period of weaning that leads to a dried inert diet. While it cannot be denied that Artemia and other types of live feed have supported hatchery production up until now, there is a global trend spanning several companies and research institutes to develop practical and scalable solutions to replace Artemia and other live prey with inert feed.

Weaning strategy with inert dry feed Studies highlighted that the replacement of Artemia with dry inert feed was quite challenging. Compound diets are well ingested at the early stage, but larvae are unable to take enough benefit from dry micro-diet. The digestibility and nutritional availability of the dry micro diet were the object of biochemical studies over more than 20 years and have shown that most of the digestive enzymes are present in young larvae and that inadequate diets can delay or maintain the secretion mechanisms for larvae with early weaning inducing mortality and poor growing. Are the dry micro-particles feed too concentrated for the digestive capacity of the larvae? Common

Seabass larvae at DPH 10 eating VivoHatch®

industrial processes, such as marumerization, spray drying, or micro extrusion, have to manage questions like homogenous composition – especially for smallsize preparation – or low leaching in the water and compromises are difficult to find with additional specifications like palatability, digestibility of particles, and water buoyancy. Dry feeds are in breaking edge with live feeds mainly due to the amount of dry matter consumed by the larvae per particle. The intake of the available nutrient concentration by the larvae is completely different and digestive behavior cannot be similar.

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FEEDS A biomimetic approach for easier weaning Future weaning improvement should consider a biomimetic approach to fit closer with live feed. Feeds that include a higher rate of moisture should be the solution for an easier transition from live feeds to dry inert feed in order to support the progressive ontogenesis development of the larvae. Wet micro diet feed has been described in the literature for years, but they face limitations, such as the industrial production process, weakness in handling oligopeptides that are needed for better digestibility but leaching very fast in water, and small size production to fit the early-stage larvae demand. This wet feed also involved thick encapsulation material that was defined as a limitation for nutrient digestion. Huddle Corp, mastering the physical chemistry interaction of nutrients, has developed a proprietary multilayer encapsulation technology that, thanks to specific nutrients encapsulation, creates a barrier to leakage with molecular wall and functional nutrients, for high availability of proteins, lipids and micronutrients. The industrial process was designed, scaled, and proofed for high quality and reproducibility of the moist micro-particles: VivoHatch®. The development of moist particles such as VivoHatch® allows a new area of possibilities in terms of formulation flexibility and micro diet properties. The dry matter of particles is higher than live feed but still with an amount of moisture that stays intermediate between live feed and dry inert feeds. Sizes of VivoHatch® are also targeting the live prey size ranges, with 50 to 150µm, then 150 to 300µm, and 300

Hatchery Feed & Management Vol 11 Issue 4 2023

FEEDS

Seabass larvae at DPH 16 eating VivoHatch®

to 500µm to give freedom to hatchery operators to use the appropriate particles that fit with their larvae physiological development. This approach allows bringing more proteins (hydrolyzed proteins highly soluble and with low molecular weight) and more qualitative lipids and PUFAs than live feeds. Besides higher nutritional quantity, the distribution of amino acids and PUFAs are following the composition of Artemia and rotifer to take advantage of biomimetic targets but with higher performance with a biomimetic approach. With this conception, higher reproducibility of nutritional targets in VivoHatch® is reached compared to the variability of the live prey that depends on their strain and the harvesting quality. VivoHatch® is shaped to remain in the water of rearing tanks while retaining nutrients to be delivered in the larvae gut. The liquid manufacturing process takes advantage of the best raw materials for larvae. Formulation involves highly soluble proteins (marine hydrolysate) and hydrophile molecules prepared and micro-structured in purified freshwater. Marine lipids and lipophile molecules, such as astaxanthin, are encapsulated with proprietary technology with natural minerals to ensure good protection against oxidation. First trials were made on seabass and turbot and confirmed that weaning was easier on modalities including VivoHatch® than with dry feeds. Zootechnical results with further data will be presented soon.

More information: Abdeslam El Harrak CEO Huddle Corp. E: contact@huddlecorp.com

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Hatchery Feed & Management Vol 11 Issue 4 2023

DISEASE & HEALTH MANAGEMENT

Helping hatcheries overcome Transparent Postlarva Disease: HACCP plans and high-quality biosecure feeds Peter Van Wyk, Craig Browdy, Chris Stock, Cao Khanh Ly, Mark Rowel Napulan, Zeigler Bros.

Credits: Craig Browdy

Since 2015, Transparent Postlarva Disease (TPD) has led to significant losses in hatcheries in Ecuador, China, and most recently, Vietnam. In larval tanks affected by TPD, larval development appears normal until larvae reach the early postlarval stages. The first symptoms typically manifest between PL2-PL4, when diseased

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shrimp exhibit the characteristic signs of an empty gut and a colorless, translucent hepatopancreas. Mortalities usually commence a few hours later and can reach 80-100% within 24-48 hours. Evidence has been presented for three different possible causes:

DISEASE & HEALTH MANAGEMENT 1. Infection by new strains of Vibrio parahaemolyticus (Zou et al., 2020; Yang et al., 2022; Tran, 2023, as cited in Tham, 2023). 2. Co-infection by a new, non-luminescent strain of V. harveyi + non-AHPND V. parahaemolyticus (Hoang, 2023). 3. Infection by a novel RNA Virus from the family Marmidae, named Baishivirus (Xu et al., 2023). A growing body of evidence suggests that most TPD outbreaks in Asia have been caused by one or more Vibrio parahaemolyticus strains distinct from the strain responsible for AHPND. Toxins produced by these Vibrio strains differ from the PirA and PirB toxins associated with AHPND. Non-luminescent V. harveyi is often, though not always, observed in tanks with TPD. While Baishivirus likely induces similar symptoms, the fact that V. parahaemolyticus isolated from shrimp with TPD can infect healthy shrimp suggests that the RNA virus is not the primary pathogen responsible for the massive mortality of PLs in Vietnam. Further information is required to conclusively identify the causative agent and transmission mode. Zeigler Vietnam recently met with customers on management strategies for the prevention and control of Transparent Postlarvae Disease (TPD) in Phan Rang, Vietnam. Peter Van Wyk, Research and Development Technical Manager at Zeigler Bros. Inc. USA, presented recent updates about TPD and shared health management practices.

Hazard Analysis Critical Control Points It is crucial for hatcheries to implement management practices focused on overall disease prevention, especially practices that can reduce risks associated with pathogenic Vibrios. It is recommended that shrimp hatcheries adopt the Hazard Analysis Critical Control Points (HACCP) approach to minimize disease risk. HACCP is a preventative system of process controls designed to identify and minimize risks associated with significant hazards to the production process. Once risk factors are defined, Critical Control Points (CCPs) can be identified, and monitoring procedures and corrective actions can be established. For hatcheries that have experienced a TPD outbreak, a complete facility disinfection and drying process is necessary. Since Vibrio forms biofilms that shield bacteria from routine chlorination, biofilm removal is

critical to the success of the disinfection step. Three methods for biofilm removal are recommended: 1) mechanical removal; 2) chemical removal and 3) electrochemical disinfection. Hatcheries are also advised to invest in highly effective seawater filtration and disinfection technologies, such as rapid sand filtration, ozone systems, ultrafiltration systems, and UV sterilizers. However, sterile seawater can be quickly colonized by Vibrio, so to minimize the opportunity for Vibrio to become established, it is recommended that disinfected seawater be treated with a highquality probiotic, such as Zeigler Rescue, at a density of 100,000 CFU/mL is adviced as soon as possible after the last disinfection step. Natural feeds used in maturation systems are known to be vectors for the introduction of pathogenic Vibrios in hatcheries. To minimize this risk, all natural feeds should be screened by PCR and frozen before use. Hatcheries are also strongly recommended to eliminate the use of live polychaetes and replace the riskiest natural feeds with formulated maturation feeds, such as Zeigler’s Redi-Mate diet. In larval rearing systems, Vibrio is most often introduced with contaminated algae cultures and Artemia nauplii fed to the larvae. Key CCPs for algae production systems are the disinfection protocols for seawater and air supplies and the algae pure cultures. Many hatcheries have improved their algae quality through the use of automated algae bioreactors. However, when hatcheries encounter problems with Vibrio contamination of algae cultures, it is beneficial to have formulated diets capable of replacing a high percentage of the algae in the larval feeding protocol, such as Zeigler’s EZ Larva, a liquid larval diet with a nutrient profile similar to that provided by diatoms. Artemia nauplii have been shown to be an important vector for the introduction of pathogenic Vibrio into larval-rearing systems. While decapsulation of Artemia cysts reduces Vibrio levels, nauplii from decapsulated cysts can still contain significant levels of pathogenic Vibrio. Zeigler offers a micro-encapsulated liquid feed product called EZ Artemia Ultra, which is a biosecure alternative to Artemia nauplii and delivers probiotics effective against Vibrio directly to the larval gut.

High-quality feeds Survival is the most significant factor influencing

Hatchery Feed & Management Vol 11 Issue 4 2023

DISEASE & HEALTH MANAGEMENT

TPD negative and positive shrimp post larvae. Credits: Cao Ly

hatchery profitability, and the best way for hatcheries to maximize profits is to invest in high-quality feeds. An economic model based on typical commercial hatchery production parameters compared a lowcost feed scenario with a high-cost feed scenario. The model demonstrated that only a 2% improvement in survival was required to offset the cost of a more expensive feed that was 40% higher than the lowcost feed. If the higher-cost feed improved survival by 5%, profits were 20% higher than for the low-cost feed scenario. For a higher-cost feed to improve profitability, it must be of higher quality. Protein efficiency (grams of PLs produced per gram of protein fed) is a much better indicator of feed quality than feed protein level. In a study comparing the performance of Zeigler’s PL diet, Z Pro, to four top-selling competitor PL diets, shrimp fed with Z Pro grew significantly faster and had significantly higher survival rates. Z Pro protein efficiency averaged 80% higher than for the competitor diets, all of which had higher protein levels than Z Pro.

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In feeds with high protein efficiencies, nutrients are efficiently converted into postlarval biomass. Excess undigested nutrients are excreted into the water, resulting in high ammonia levels. Ammonia is an excellent nitrogen source for Vibrio and, therefore, high ammonia levels can lead to higher populations of Vibrio in the water column. Higher ammonia levels are stressful for postlarvae, resulting in slower growth and reduced resistance to Vibrio challenges. PLs fed with high-quality feeds are also more likely to yield higher survivals in nursery systems. The additional profits generated by the improvements in survival in both the hatchery and nursery systems highlight the importance of using high-quality feeds, especially during times of low PL prices. Zeigler is proactively assisting hatcheries in overcoming this latest disease challenge by enhancing biosecurity through the development of HAACP plans, while also providing cutting-edge probiotic and feed solutions to help hatcheries produce healthy, robust larvae capable of withstanding disease challenges.

DISEASE & HEALTH MANAGEMENT References Hoang, T. 2023. Co-infection of Vibrio in shrimp postlarvae. Linkedin: www.linkedin.com Tham, H. 2023. Warning of new disease appearing on white leg shrimp. Vietnam Agriculture website. Xu A, Xu S, Tu Q, et al. A novel virus in the family Marnaviridae as a potential pathogen of Penaeus vannamei glass post-larvae disease. Virus Res. 2023;324:199026. doi:10.1016/j.virusres.2022.199026. Yang F, Xu LM, Huang WZ, Li F. 2022. H ighly lethal Vibrio parahaemolyticus strains cause acute mortality in Penaeus vannamei post-larvae. Aquaculture 548:737605. Zou, Y., Xie, G., Jia, T., Xu, T., Wang, C., Wan, X., Li, Y., Luo, K., Bian, X., Wang, X., Kong, J., Zhang, Q., 2020. Determination of the infectious agent of translucent post larva disease (TPD) in Penaeus vannamei. Pathogens 9 (9).

More information: Peter Van Wyk R&D Technical Manager Zeigler Bros.

Craig L. Browdy Director R&D Zeigler Bros.

Chris Stock Global Director Aquaculture Sales Zeigler Bros. Cao Khanh Ly Technical Sales Manager, Vietnam Zeigler Bros. Mark Rowel Napulan Asia Sales Manager Zeigler Bros. E: mark.napulan@zeiglerfeed.com

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Hatchery Feed & Management Vol 11 Issue 4 2023

DISEASE & HEALTH MANAGEMENT

What is the best method for early warning and prevention of WSSV in shrimp farming? Melony Sellars, Genics

White spot disease (WSD) is a highly contagious viral shrimp disease. First detected in East Asia in the early 1990s, it has since spread worldwide. Australia was considered free of White Spot Syndrome Virus (WSSV) until 2016. At that time, Southeast Queensland had an incursion that started from imported uncooked commodities being used as recreational fishing bait in waterways adjacent to Penaeus monodon shrimp farms. The biosecurity response of the government resulted in all stock in the region being culled including 12th generation selectively bred breeding lines that were

Hatchery Feed & Management Vol 11 Issue 4 2023

producing three times more tonnes per hectare yearon-year compared to wild spawned larvae, with the added benefit of being highly robust and tolerant to endemic pathogens. With a movement restriction area (MRA) in place, these farms stayed dry for two years and one farm had another occurrence of WSSV afterward. This MRA region is now considered to have WSSV as endemic in natural waterways. In late 2022, WSSV was detected on a shrimp farm in Northern New South Wales (NSW) in locally caught broodstock. Since then, WSSV has been detected in

DISEASE & HEALTH MANAGEMENT

Areas affected by WSSV in Australia

three Northern NSW shrimp farms in early 2023. Today (November 2023), shrimp farms in the state of NSW are not operational.

Biosecurity procedures With WSSV on the doorstep of Australia’s coastlines where shrimp are cultured, the industry has been advised to be prepared and practice the highest biosecurity standards to prevent an incursion on their operations. One such example of success is that of Gold Coast Marine Aquaculture in Queensland where water treatment at the point of entry to the farm occurs followed by 50 µm drum filtration of all incoming water. The movement of shrimp from one area to another, or between companies, requires strict translocation or movement permits and highly sensitive PCR testing. Australia’s industry-level access to pathogen testing for reportable and exotic pathogens is highly regulated, and quite possibly the highest standards globally. Point of Care (PoC), pond-side test kits and field-deployable PCR-based tests are not approved for use in Australia for

the purpose of early pathogen detection and early risk mitigation when it comes to an exotic like WSSV Genics Shrimp MultiPathTM testing platform is accessed by 100% of the Australian industry for the purposes of translocation testing, and in areas where WSSV has previously occurred (South East Qld and Northern NSW), is the only commercial test available for surveillance of WSSV in apparently healthy shrimp for the purposes of early detection and early risk mitigation. In Australia, no other commercial test has reached the required standards to be approved for such purposes. Australian farms have many other biosecurity practices in place, such as waiting 72 hours between farm sites for visitors, ensuring clean clothing and shoes are worn, etc. Suppliers of aqua products are also very conscious of their responsibility to practice good biosecurity when delivering products and meeting with the industry. Importantly, the industry representative group, the Australian Prawn Farmers Association, ensures the industry is informed and up to date with the best biosecurity practices.

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DISEASE & HEALTH MANAGEMENT In terms of limit of detection or analytical sensitivity (ASe) “PoC test ASe was reduced 10-fold to 10,000fold compared to the laboratory reference qPCRs”. These comparisons included some of the world’s most commonly referred to and utilized test kits and field-deployable PCRs. In simple terms, the evaluated PoC kits and PCR systems that were compared to the real-time PCR are not suitable for early detection and early risk mitigation. Such test kits may, however, be good for the purpose of confirming animals that are clinically sick, which is too late for early detection and early risk mitigation. The take-home message for the global shrimp industry is that the real performance of PoC systems may not be exactly as per the claims on the packaging and require very careful interpretation.

Finding the most reliable test A recent Fisheries Research and Development (FRDC) report, authored by the CSIRO Australian Centre for Disease Preparedness (ACDP) and colleagues (FRDC report 2019-089), compared WSSV PoC and field-deployable PCR WSSV test kits to WOAH and CSIRO reference WSSV real-time PCR. They conclude that “overall, performance of the WSSV PoC tests varied widely and was generally reduced compared to laboratory-based reference tests, however, this is not unexpected given the trade-off between test performance and the simplified design and operational characteristics that make PoC tests appropriate for field use.”

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What are the alternatives for farmers? The recommendation for good biosecurity practices is early pathogen detection using highly sensitive testing platforms within broodstock cohorts, during nursery production and during grow-out by PCR testing of a statistically significant population size and target organs for sensitive pathogen detection, such as the Shrimp MultiPath platform. In terms of access to fit-for-purpose testing that is sensitive and cost-effective for this early detection purpose, shrimp producers in 45 countries already access the Shrimp MultiPath platform from Genics Accredited Laboratories in Australia. Shipping takes three days from most parts of the world and Genics returns data within 48 hours. The new my.genics.com.au portal allows easy online submission and shipment booking, with DHL picking up from your shrimp production site and delivering to the laboratory in a door-to-door service. New customers simply request an organization account at genics.com.au

DISEASE & HEALTH MANAGEMENT and our digital services team will have you set up within 12-24 hours. Other good biosecurity practices should be a daily routine. Biosecurity does not have to be made complex, it can be simple steps and procedures that help reduce the risk of a pathogen incursion. As one example, when moving between broodstock centers or hatchery facilities, ideally, leave at least 72 hours between sites and ensure that shoes are disinfected with bleach and clean laundered clothes are worn. Spraying hands regularly between tanks/ponds and between sheds with 70-80% ethanol is also good practice and helps reduce the risk of transmission within a facility. There are many simple procedures like these that increase your biosecurity.

Tricks to keep in mind Here are some insights on the tricks of the trade with PoC testing and field-deployable PCR kits to look out for: • The validation on synthetic templates not shrimp DNA and RNA as a farmer would be using. This helps make the tests seemingly look more sensitive than they actually are when used on shrimp tissue. Sensitivity is very important for early detection purposes and by way of example, an assay may have a limit of detection of 5 copies per reaction on a synthetic template but it might increase to 40-80 copies when using shrimp DNA or RNA. At 40-80 copies, the test is simply not fit for the purpose of early detection and early risk mitigation. • Miniaturization of regent volumes. While this might sound smart, it is done to reduce the cost of making the test and it reduces the ability of finding very low pathogen numbers. If you miniaturize you also need to load less DNA and RNA which means you reduce your chances of finding low-load pathogens in your sample. • Lack of DNA and/or RNA quality controls for the actual shrimp DNA and RNA. Some kits don’t do controls at all, and some do an internal control which is not shrimp DNA and RNA but makes it sound like it is. The reason you need a shrimp DNA and/or RNA control is because shrimp tissue contains PCR inhibitors like chitin which can stop a PCR reaction from working, with the risk of a false negative result if not run properly. Beware of kits that claim an internal control when they provide the template for the control, the template must be your shrimp DNA and or RNA from

your sample. If you are testing DNA pathogens like WSSV you need a shrimp DNA control. If you are testing shrimp RNA pathogens like IMNV you need shrimp RNA control. • Very short best-before or expiry dates on kits mean you are almost always operating outside of a manufacturer-recommended range and this is something to watch out for.

Conclusions The report shines a light on some of the issues with PoC testing and field-deployable PCR kits that Genics has been communicating to the industry for the past four years. There is a reason Shrimp MultiPath is run in an accredited highly controlled laboratory with trained experts – this is currently the only way farmers can be re-assured of very sensitive, accurate pathogen testing results for multiple pathogens. All other technologies are not robust enough and cannot be performed in such a cost-effective way. PoC or field-deployable PCR is simply not suitable for early detection and early risk mitigation. “Tassal is proud to be working with the Genics team in our prawn operations. Genics provides professional, fast and cost-effective pathogen diagnostics for prawns that are of the highest standards. Genics has provided us with expertise, sample logistics and a one-stop shop for diagnostic sampling,” said Colin Johnston, senior veterinarian at Tassal. Shrimp MultiPath is the only tool for cost-effective multiple pathogen detection for the purposes of early detection and early risk mitigation in shrimp globally. Our friendly team is here every step of the way and will work with any producer to design a statistically significant sample plan that is fit for purpose for good biosecurity practices.

More information: Dr. Melony Sellars CEO & Managing Director Genics E: info@genics.com.au

Hatchery Feed & Management Vol 11 Issue 4 2023

DISEASE & HEALTH MANAGEMENT

What role does the health of shrimp post larvae (PLs) play in farm outcome? Stephen G. Newman, Aquaintech Inc.

Clean shrimp indoor facility

The terms microbiome and microbiota are frequently confused with each other. The microbiota is a subset of the microbiome. It refers to the microorganisms that are present in each environment. The term microbiome refers to the total genome and gene products of all the bacteria, bacteriophage, fungi, protozoa, and viruses that are present in a specific environment. This can be in and on an animal or a plant. It can also

Hatchery Feed & Management Vol 11 Issue 4 2023

refer to any element of the environment including objects. As applied to aquaculture most often it is used in reference to what is present internally as well as the external surfaces of a given aquatic animal. It also refers to the specific composition of individual elements of a production environment, such as the sediments, the water column, etc. A given microbiome is really just a subset of a much larger

DISEASE & HEALTH MANAGEMENT correlate with the overall health of the population. Whether we will be able to link specific elements of the microbiome causally with health, disease resistance and/or tolerance is the challenge. Correlation is not causation.

ecosystem, just as the microbiota are components or elements of the microbiome. Not all that long ago much of the microbiome was hidden from science. It was widely held that we could culture most of the bacterial and fungal components on artificial media. Many workers reported broad changes in the microbiome based on observations of how experimental protocols altered what could be cultured. Using much more sophisticated tools today we can characterize many of the elements of a given microbiome, the vast majority of which, we now know, cannot be cultured. This, for the first time, has allowed us to see how complex the microbiota/microbiome is and how it can be affected by the use of many different materials in the feed and in the environment. We have a much clearer, albeit evolving, idea of what microbiota are elements of the microbiome. There are some indications that specific microbiota may be used as indicators of animal fitness. Given the extreme variability of production paradigms and environments, any generalization of this nature is questionable, although there is data that suggests that healthy animals may have microbiomes that one can

Shrimp hatchery production Currently, the exact tonnage of farmed shrimp being produced globally each year can only be approximated. Production is somewhere between 3.8 and 6 million MT with the numbers being source dependent. Using the higher figure, to produce the 6 million MTs of shrimp that will be farmed globally in 2023, an estimated 600 billion post larvae (PLs) would have had to be produced (assumes 20 g average weight at harvest, 50% survival in the hatchery). This production is spread across thousands of hatcheries in dozens of countries. The state-of-the-art production of post-larval shrimp remains, for the most part, relatively primitive. Larger operations may produce a billion or more PLs a month although this is the exception with most production coming from smaller hatcheries. Biosecurity is weak in general regardless of the size of the facility and those who operate them all too often neglect the tools of science (Newman personal observations). Widespread use of disinfectants can damage the microbiota and create niches for rapidly reproducing bacteria, such as Vibrios, to dominate. A major source of diseases in farmed shrimp is a result of the carry-over of obligate pathogens from broodstock. PCR testing of populations using the standard statistical approach can result in animals carrying pathogens below the threshold. For example, when there is a 98% chance of finding a given pathogen when screened for using non-pooled samples, appropriate primers, and conditions conducive to maximum sensitivity, 2% of the population can still be carriers, i.e. 20,000 out of a million PLs. These will continue to spread pathogens, both those that are present historically and potentially new ones that are cropping up with a consistent frequency. Broodstock should be held under lifelong quarantine, screened repeatedly by sensitive and specific PCR primers with moribund animals examined clinically including thorough examination by histopathology to determine the cause. Endogenous viral elements (EVEs) are increasingly being reported and this can

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DISEASE & HEALTH MANAGEMENT lead to costly false positives. It is critical that the right primers are used. Eliminating obligate pathogens from the broodstock ensures that nauplii, pre-larval and PLs are not carrying them into their respective production systems.

Vibriosis in shrimp culture One of the most common reported problems in hatcheries is vibriosis due to infections with Vibrio bacteria. Vibrios are ubiquitous in marine and, to a lesser extent, freshwater environments. They serve an important function in the recycling of chitin, the structural component of crustacean exoskeletons, among other things. Some are human pathogens (Vibrio parahaemolyticus, Vibrio cholerae) and others are aquatic animal pathogens (Vibrio parahaemolyticus, Vibrio anguillarum, etc.). As of this writing, some 149 distinct species have been identified with many thousands of variant strains. Note that many bacteria can cause disease in farmed shrimp, not just in the hatchery, but on the farm as well. These include Aeromonas, Pseudomonas, Clostridium, Propigenium, Streptococcus and many others. Focusing exclusively on Vibrios as being the source of problems, although widespread, is not consistent with optimum results. Attention needs to be paid to known pathogens and ensuring that their presence is minimized by breaking the cycle between broodstock and the farm and minimizing the presence of known vectors in farms as well as creating a production environment that ensures reduced stress on the animals. Perhaps the most widely Vibrio-linked problem in shrimp hatcheries is known as the zoea syndrome. Zoea are the first feeding stage of larval shrimp and large mortalities can occur at this highly sensitive stage if Vibrio loads are not adequately controlled. The first effort to control the impact of Vibrios in shrimp hatcheries via the use of microbiota manipulation was developed by Giovanni Chasin and published by Garriques in Ecuador in the early 1990s. They reported that Vibrio strains from the wild that were able to degrade sucrose on the widely used selective media for Vibrios, thiosulfate-citrate-bile salts-sucrose agar (TCBS), i.e. they formed yellow colonies when added in large numbers to hatchery tanks were able to dramatically reduce the severity of the disease. This approach has some challenges when applied to the

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field. Unfortunately, the assumption was that these Vibrios, typically Vibrio alginolyticus, were not virulent. Animals were routinely tested for susceptibility to verify this. However, failure to understand how diverse this taxon is and how readily they exchange genetic material has resulted in hatcheries losing entire production runs using a similar approach. The ability to degrade sucrose has nothing to do with virulence. Other important pathogens are toxigenic strains of V. parahaemolyticus. The combination of PirA/PirB toxins has wreaked havoc globally and continues to be problematic. These toxins have been found in several other species and are highly specific for the tubules in the hepatopancreas. Damage can range from being barely evident to death. Often secondary bacterial infections kill. Recently, a relatively new syndrome, transparent shrimp disease, has been associated with other strains of toxigenic V. parahaemolyticus. Given the ubiquitous nature of Vibrios, this strain is quite likely to spread as much as the PirA- and PirBproducing strains have.

Microbiota manipulation We are still in the early stages of this being a truly science-based protocol. Knowing what to add, where to add it, how much to add and how often are only a few of the challenges. Perhaps the greatest single challenge is that many of the companies that sell bacteria as probiotics are selling products for bioremediation. Probiotics are living bacteria, ingested orally, that alter the microbiome (the microbiota) and have a positive impact on animal health. While there are some claims that this is what is occurring the field results do not seem to verify that there is indeed a probiotic effect as defined above. Shrimp consume large amounts of bacteria as their natural food source. This practice of adding any number of a wide variety of bacteria continues despite potential hazards. There is a widespread failure to appreciate that bacteria readily exchange genetic material, sometimes at high frequencies, and that this can lead to acute problems as a result of the exchange of genetic material between virulent obligately pathogenic strains and currently benign strains. Typically, this is between bacteria with some genetic similarity, but this is not always the case. The practice of adding as many different sources of bacteria as there are vendors poses a risk to the stability

DISEASE & HEALTH MANAGEMENT

Figure 1. Impact of Bacillus (PRO4000X) on (yellow on TCBS) Vibrio loads in hatchery tanks.

of the pond and hatchery ecology as well. Bacteria compete against each other and the strains of VP that cause AHPNS have a very effective tool for doing this. With this in mind, the ability of several spore-forming gram-positive bacteria (Bacillus species) were tested for their ability to impact Vibrio loads in a shrimp hatchery in India. A tableted product (PRO4000X) containing equal proportions of specifically selected proprietary strains of Bacillus subtilis and B. licheniformis was added to hatchery tanks and the impacts on total Vibrio loads determined (Fig. 1, 2). These tests demonstrated that these proprietary Bacillus strains when added daily to shrimp hatchery tanks were able to dramatically lower the total Vibrio loads and keep them low. This was an example of microbiota manipulation in a production environment

that had a dramatic impact on the presence of presumptive pathogens that routinely have a negatively impact on shrimp hatchery production. The hatchery personnel noted that the tanks were much cleaner, that they were able to stop exchanging water and that the animals in the experimental tanks were cleaner, stronger, grew better and were free from vibriosis problems. These examples of microbiota manipulation show a clear cut, although not permanent, impact. The Bacillus spores had to be added daily to ensure that levels did not decline to the point where they no longer resulted in the desired outcome, i.e. reduction of Vibrio loads (Habeeb Rahman-personal communication). When the Bacillus spores are no longer being added the impact will disappear. It is not likely that the Bacillus have

Figure 2. Impact of Bacillus (PRO4000X) on (green on TCBS) Vibrio loads in hatchery tanks.

Hatchery Feed & Management Vol 11 Issue 4 2023

DISEASE & HEALTH MANAGEMENT become a stable component of the microbiota. One would expect that daily addition would not be needed if the added Bacillus strains were able to become stable elements of the microbiota/microbiome. These tests demonstrate that in shrimp hatchery tanks it is possible to alter the microbiota in a manner that has a beneficial impact on the overall production, significantly altering the composition of the bacteria normally present. While the exact mechanisms remain to be elucidated, the evidence suggests that we are looking at a simple case where the added Bacillus spores upon germination compete against resident species for nutrients. This effect has also been noted in shrimp ponds as well (Habeeb Rahman personal communication). Similar experiments have been carried out in production ponds demonstrating that this approach can impact the presence of potential pathogens in grow-out ponds. The reduction of potential pathogens is a valuable tool and an important step in minimizing the impact of animal health challenges on production. However, this does not occur in a void. Broodstock must be produced in a manner that ensures that no pathogens are present. Biosecure production protocols must be present throughout the PL production process to ensure that Artemia and algae culture are not introducing pathogens. Open to the air systems can easily be contaminated. Stocking PLs that do not carry high loads of obligate and opportunistic pathogens is essential for sustainable shrimp production.

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Stocking protocols must be geared toward minimizing stress and the production environment should be free of accumulated organic matter, and well aerated with automatic feeders programmed to minimize waste, feeds should be designed to minimize waste by unnecessary grinding of feed before ingestion with highly digestible ingredients and adequate levels of micro and macronutrients. The goal should be to create an environment that is conducive to high survival and allows the animals to realize their genetic potential, growing as rapidly as they can. Shorter cycles allow for more cycles per year. Knowing what is being stocked both quantitatively and qualitatively is the only way to know what the true outcome is. Efforts to alter the microbiota have been successful using Bacillus species in the hatchery and the farm with favorable results. These are short-term changes. High-quality, pathogen-free PLs are an integral part of sustainable production.

More information: Stephen G. Newman Ph.D. President and CEO Aquaintech Inc. E: sgnewm@aqua-in-tech.com

DISEASE & HEALTH MANAGEMENT

Unlocking aquaculture success: Gut microbiota management for optimal health and productivity François Jégou, ADM Animal Nutrition

Aquaculture has been the fastest-expanding food production sector globally for the past 50 years, growing at an average of 5.3% per year since the turn of the century (Dongyu QU, FAO, 2021). However, this success story, based mainly on a few species such as Pacific whiteleg shrimp (L. vannamei), tilapia, carp, salmon and catfish, is continuously challenged by daily realities, including multiple and complexly associated infectious pressures – primary and opportunistic, impacting farming business economics and survivability. When it comes to aquaculture performance, health and profitability, most farmers know how important a successful early start can be in future life stages. Therefore, reliable, stable and consistent sourcing of post-larvae or fingerlings in order to ensure a smooth

and efficient transition to pre-growth and grow-out performance is critical. Aquaculture by definition means rearing groups of living organisms in water, of which quantity, quality and constancy may be highly variable. These irregularities represent significant stress impacting their microbiota, which constitutes one of the first functional barriers to maintaining the organism’s homeostasis. These stressors need to be overcome individually and collectively by such groups of aquatic organisms, that may to a certain extent be deficient, especially when it comes to immature life stages. Such homeostatic imbalance may often last for a portion or the entire production cycle, leading to several hazards in terms of farm health and thus performance.

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DISEASE & HEALTH MANAGEMENT Beyond its primary function in digestion, the intestine plays a fundamental role in immunity. Indeed, besides direct inhibition, fish gut microbiota has essential functions in epithelial renewal and maturation, which in turn regulate immune responses (Gomez & Balcazar, 2008; Wang et al., 2017). Both activities are intrinsically related via the resulting microbiota, its maintenance and its optimization.

the immune response, reducing oxidative stress, or protecting the intestinal epithelium, allow for stabilization of the gut microbiota, as well as reduced chances for multiplication and colonization of noxious organisms, and optimizes microbiota activities to promote fish and shrimp health and performance. Illustrations of these strategies may be brought through trials ADM carried out on main challenges facing global aquaculture, including WSSV (White Gut microbiota and feed additives Spot Syndrome Virus) disease and AHPND (Acute Strategies involving blends of selected weak and Hepatopancreatic Necrosis Disease) or EMS (Early strong organic acids, or compounds favoring firmicutes Mortality Syndrome) in shrimp, and Streptococcosis, populations while reducing proteobacteria, regulating which affects several key fish species worldwide such as tilapia, barramundi, grouper and more. Due to microbiota optimization, the same feed additives bring significant benefits to growth and feed efficiency in usual field conditions. Overleaf are examples of results obtained with two feed additives from ADM’s portfolio, both in challenged and usual conditions. Other range products play complementary roles within the organism, such as reducing oxidative stress and intestinal inflammation, epithelium protection, helping organisms better cope with parasitic stress, toxinic stress or regulating the overall immune response. In a trial examining the results of B-Safe, a patented mix of activated clay and Figure 1. Survival of shrimp feed with B-Safe exposed to a WSSV challenge vegetal extracts, researchers found that a dosage of 5kg/MT feed resulted in a 138% increase (p<0.05), a significantly higher survival rate within six weeks, for shrimp exposed to an infectious WSSV challenge (Fig. 1). A trial with tilapia that utilized B-Safe at the same dosage of 5kg/MT feed allowed for a 37% higher survival rate four weeks after being exposed to a Streptococcus agalactiae cohabitant challenge test. Blood samples also showed significant two-fold concentrations in lymphocytes, as compared to control inoculated tilapia, as well as higher red Figure 2. Survival of tilapia feed with B-Safe exposed to a Streptococcus challenge blood cell counts (Fig. 2). Additionally,

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DISEASE & HEALTH MANAGEMENT

Figure 3. Survival of shrimp fed with Fitactif exposed to an AHPND challenge

tilapia fed with B-Safe incorporated at the dosage of 3kg/MT feed for 50 days expressed significant, 11% higher growth and 11.2% improved feed efficiency compared to control, resulting in a net return on investment (ROI) of 11:1. ADM also conducted a trial with shrimp that administered Fitactif, a blend of selected short and medium chain fatty acids at the dosage of 6kg/MT feed, which resulted in a significant 45% gained survival rate three weeks after being exposed to an AHPND-Vibrio

parahaemolyticus immersion challenge. Interestingly, these results were similar to those obtained with antibiotics florfenicol or oxytetracycline, although Fitactif is not an antimicrobial solution. Therefore, Fitactif does not contribute to antimicrobial resistance risk (Fig. 3). Furthermore, research demonstrates that grow-out shrimp supplemented with Fitactif at 3kg/MT feed for 48 days exerted 13% higher growth performance compared to untreated shrimp. This generated a ROI of 11:1.

Figure 4. Effects of different treatments on shrimp microbiota. Upper chart: Intestine; Lower chart: Hepatopancreas

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DISEASE & HEALTH MANAGEMENT microbiota management results from both careful selection of feed additives, as well as precise nutrition consecutive to specific feed formulation, adapted to each physiological life stage and condition. For example, while optimal growth in early life mainly needs the correct supply of digestible protein (DP) much more than total protein, it is mostly dependent on digestible energy (DE) in later stages. Moreover, proper ratios of DP and DE are crucial in both stages (Fig. 5). Additionally, seasonality often has great impacts on the organism and its environment, physically and biologically. Farmers should review the effects of seasonality and adapt feeds accordingly. Through an adequate qualitative and quantitative selection of raw materials and nutrients adjusted accordingly to each relevant encountered situation, precise nutrition supports growth, feed efficiency, gut health, farm sustainability and profitability.

Conclusions ADM consistently focuses on different and synergistic ways to optimize specific functions impacting the gut microbiota in a positive way, stabilizing it for the benefit of continuous growth and health. This is achieved both by means of precise nutrition, specific to each physiological life stage and condition, as well Figure 5. Proper ratios of DP and DE are crucial in early and later stages as dietary and non-antimicrobial tools helping in the organism’s homeostasis. Results of such As detailed in Figure 4, metagenomics represents a an approach show significant improvements in survival, state-of-the-art study of genetic material recovered growth and feed efficiency in different situations – directly from environmental or clinical samples by from common commercial to challenged conditions, sequencing method. This graphic visualizes the effects infectious or non-infectious – and set the way forward of different treatments on microbiota in various to aquaculture profitability and sustainability. conditions and provides appropriate help in their judicious selection considering the given situation. In this case, the upper chart shows intestine samples and the lower shows hepatopancreas samples after a WSSV More information: challenge in shrimp. François Jégou Gut microbiota and feed formulation Bringing benefit during the entire production cycle in normal as well as in challenging conditions, optimized

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Aquaculture Technical Manager ADM Animal Nutrition E. francois.jegou@adm.com

WATER QUALITY

Improving fish welfare at the hatchery through water quality Jakob Surber, Dryden Aqua

Figure 1. Aquaculture hatchery media system

Water quality sets the foundation for good fish health and welfare. While many important factors serve as indicators of good water quality, the ones that are talked about most often are the levels of oxygen, CO2, ammonia, nitrate, and pH. This makes sense, as these are the parameters that, if lacking, will kill the fish the fastest. Less talked about, but still highly detrimental, are total suspended solids (TSS). Acceptable TSS levels in a grow-out system vary by species. However, as a rule of thumb, the recommendation is to stay between 5-10mg of TSS per liter. A value that is rarely reached by many systems.

Effects of high TSS High TSS has a range of direct and indirect effects on fish welfare.

• Particles can clog or physically damage a fish’s gills. Apart from the damage itself, the physical stress increases the fish’s susceptibility to other pathogens. • Particles in suspension can be many things but are often organics that feed bacterial proliferation. • Organics mechanically clog biofilter media, decreasing the available surface area for aerobic nitrification. • T he organic load in the biofilter also creates favorable conditions for unwanted heterotrophic bacterial growth. The heterotrophs compete with the autotrophic nitrifying bacteria and can form an anoxic sludge on the bottom of the biofilter. • Organic particles, such as feces, feed particles, and bacterial floc from the biofilter use up oxygen during metabolization if they are not mechanically removed from the water column.

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Figure 2. Filtration spectrum of different separation processes

• Particles can always act as a vector and/or breeding ground for pathogens. • The particles may be pathogens (such as Cryptocaryon or Vibrio) or parasites themselves.

Why finer filtration? Lowering the amount of TSS increases water quality and, therefore, leads to healthier fish. Many farms rely on quite coarse mechanical filtration such as drum filters (typically upwards of 50 microns), which may or may not be aided by a side loop foam fractionator. This leaves a large range of fines that remain in the water. Also, drum filters were originally designed for mining applications to handle solid particles. Soft organics are pushed through the sieve

even at quite low differential pressures, creating large amounts of fines. While full grow-out RAS often requires a drum filter due to its small footprint compared to the large water volumes it processes, hatchery systems operate under different conditions. On one hand, the amount of water, and the stocking density (and thus organic load) are lower in hatchery systems. On the other hand, larvae and fingerlings are much more susceptible than adult fish.

What filter to use? Due to the lower water volumes, and higher sensitivity of the inhabitants, finer filtration is possible and desirable. For finer filtration, there are three

Table 1. Comparison of different water filters

Drum filters

Media filters

Cartridge & bag filters

Membrane filtration

Throughput

+++

Filtration performance (µm)

++-+++

+++

++++

Pressure loss

+-x

xxx

Backwash

+++

Backwash energy usage

n/a

Backwash water usage

+-++

n/a

Pathogen removal Best suited for

xxx

+-++

++++

Large throughput course filtration

Medium throughput fine filtration

Low throughput fine filtration

Low throughput ultrafine filtration

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WATER QUALITY partner, implemented several full AFM filtration systems for their customers, allowing the increase of bio-load by 20%, while reportedly decreasing mortality by 10% in seabream larvae. In their weaning unit, a 50% side stream filtration through AFM allowed them to reduce water replacement by 60%, while simultaneously decreasing mortality by 40% Figure 3. Comparative of particle size removal performance of AFM and sand filters Full f ines f iltration in hatcheries leads to options: membrane filters, cartridge/bag filters or considerable benefits: media Filters (Table 1). • Drastically lowering the TSS in fish tanks, including the Membrane filters offer spectacularly fine filtration bacterial floc of the MBBR. (0.01µm or even smaller). However, they need • Allowing for more effective operation of the MBBR, high pressure and thus large amounts of energy by preventing biological and mechanical fouling and to operate. Without prefiltration, they will clog lowering BOD. quickly. Backwashing is limited, requires aggressive • Increasing the carrying capacity of the system. chemicals, and cannot prevent permanent protection • It may lower turbidity enough to forget ozonation in from fouling. favor of UV, removing a risk factor for man and animal. Cartridge and bag filters can also offer very fine • Improving biosecurity by mechanical filtration of filtration (down to 0.5µm), but they need to be manually pathogens from the water column, reducing the need cleaned, which is often ignored, leading to deteriorating for chemical treatment, and lowering mortality. filtration performance. With proper filter hydraulics and the right filter media, Conclusion media filters can filter down to 1µm. Ideally, they are Aquatic animals of every life stage will always benefit backwashed automatically at a pressure differential of from the highest possible water quality. While 0.5bar to prevent channeling inside the filter. To ensure integrating a highly effective filtration system does not optimal filtration, a filter that is built to DIN standard come cheap, we believe that prevention will always 19605 should preferably be used. Small domestic be cheaper treating symptoms time after time. Due to swimming pool filters or, horizontal sand filters, their low water flows, but highly susceptible inhabitants, which are often used for small hatcheries or research hatcheries are uniquely suited to 100% media filtration. systems, are not designed for the high TSS loads of an aquaculture system. While sand will bio-foul eventually, as long as the manufacturer’s protocols are respected, bio-resistant media like AFM will deliver consistent 1-µm filtration for decades.

The case for 100% media filtration in hatchery systems The relatively low water flows in hatchery systems make them uniquely suited to finer filtration. Many different combinations, and arrangements of water treatment units are possible. Adec, our Turkish

More information: Jakob Surber Technical Specialist Dryden Aqua E: info@drydenaqua.com

Hatchery Feed & Management Vol 11 Issue 4 2023

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Drum filters: The key component for ensuring clean water Kurt Carlsen, CMAqua Caution against comparing drum filters and disc filters Turbulent waters at the mechanical filtration stage will lower the actual filtration result dramatically. To achieve excellent water quality, it is crucial to remove particles rather than crush them. Figure 1 illustrates how a gentle 80-micron filtration process can reduce particle load by 90% in a fish farm – significantly

higher than the 68% achieved with a more turbulent particle treatment. This substantial difference is also seen by the fact that you need 15-micron filtration turbulent waters to match 80-micron to get the same filtration efficiency. This creates a substantial gap in water quality or investment. There is no good choice moving forward if turbulent water treatment is ignored.

Minimal turbulence with drum filters Drum filters feature large openings at their entrance, allowing particles to flow gently into the filter and be captured by the filter cloth. Leading drum filter manufacturers include grid cells in the filter cloth, retaining particles until they are flushed away by the backwash system into a sludge tray. Due to the nature of drum filters and the gentle handling of particles within the cells, implementing intelligent control in the backwash system makes practical sense. Intelligent control significantly reduces backwash water consumption, activated only when the filter capacity is fully utilized. High turbulence with disc filters Disc filters feature smaller entrances, causing particles to encounter edges at high flow velocities. Unlike the filter cloth in drum filters, the filter cloth in disc filters lacks cells. As particles slide around during rotation, they will break with such rough handling. The vertical backwash in disc filters, along with the smooth filter cloth without cells, makes it impossible to implement intelligent backwash control due to particles sliding on the cloth. The nature of the disc filter construction ultimately leads to particle grinding and, consequently, higher backwash water usage and rough handling of the fragile particles.

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WATER QUALITY

Figure 1. Factors influencing suspended solids size in aquacultu reauthored by Dr. Alexander Brinker and Dr. Roland Rösch from the Fisheries Research Station of Baden-Württemberg in 2004. PSDs before and after passing a 0.7m waterfall at the end of raceway 1 (basin 145). The bracket shows the difference of 21.8 basis points between the two PSDs at 80 um (drum filter screen size).

mist-free environment, corrosion-resistant materials, space-saving designs, or reduced backwash water usage, CM Aqua has you covered. • PE tops significantly reduce noise levels and prevent mist leakage during backwash. • X-series is entirely corrosion-free, with no metal components. • XL-series boasts exceptional capacity with a minimal footprint. • IC controls result in three times less backwash water consumption compared to standard drum filter control. • Direct Drive Gear Wheel (DDGW) employs high-tech polymer gear wheels that require no maintenance or lubrication apart from water.

Efficient particle removal Gentle treatment of the particles can remove up to three times as many particles in RAS and outlets. It is simply sad to see the re-introduction of disc filters, sedimentation and other filtration systems, not focusing on this most critical issue in filtration. Advantages of drum filters Drum filters have a strong historical connection to aquaculture. Firstly, the filtration is optimal, proven over the past 30 years. Many fish farmers select drum filters due to maintenance considerations. They focus on keeping the water quality optimal for their fish, prioritizing fish health, fish growth and welfare. CM Aqua contributes to this goal with well-tested and efficient solutions. CM Aqua filters consistently maintain clean water with highly predictable results. They significantly reduce maintenance, decreasing the labor hours required for facility upkeep and inspecting the filters is extremely straightforward due to their simple design. Diverse range of drum filters Drum filters are available in numerous variations within the HEX series. Whether you seek low noise levels, a

More information: Kurt Carlsen Sales Director & Founder CMAqua E: kc@cmaqua.dk

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WATER QUALITY

Harvest Rake helps fish hatchery maintain optimal conditions for trout farming Steve Dill, Mark Hickok, Duperon Corporation

Background Built in 1974, the Jim Hinkle Spring River State Fish Hatchery is on a seven-acre island in the Spring River near Mammoth Spring, Arkansas, USA. The hatchery is one of the largest state-owned trout-producing facilities in the southeastern United States and is the Arkansas Game and Fish Commission’s only cold-water facility. Every year, the hatchery produces 650,000 to 800,000 rainbow trout for Arkansas tailwater trout streams and

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spring creeks, and it provides trout for the seasonal Family and Community Trout Fishing Program and the winter trout-stocking program in southern Arkansas. Future additions to the hatchery include brown trout and tiger trout. Water for gravity-fed hatchery comes from the Spring River near the Spring River Dam at a rate of about 70,000 gallons per minute. The hatchery consists of 56 tanks, 21 linear raceways, 11 fiberglass siloes and 24

WATER QUALITY

round concrete siloes. The dam was built around 1910 to generate electricity for Mammoth Spring but is no longer operational as a hydroelectric dam.

Trout require clean, moving water to thrive; the prior solution was labor-intensive Removing debris carried by the river before its water enters the hatchery is important to keep the waters at optimal conditions for fish farming. Trout depend on moving water for survival, and debris can slow water flow to a point that it’s not healthy for the fish. The freshwater intake at this facility has a high volume of weeds, stringy material and vegetation that jeopardizes the water volume for the downstream fish hatchery production. The performance of screening equipment ahead of the production process is vital to the complete operation of the facility. To remove this debris, the hatchery was using an aging, locally constructed screening device that required a high amount of maintenance and labor. Especially

during heavy rain and floods, cleaning the screens was an all-hands-on-deck event that required manual debris removal to keep the river flowing through to the hatchery. In extreme circumstances, the screens would have to be removed, leaving it all up to the inlet bar grate to keep the hatchery from getting overloaded with debris. And afterward, sometimes for days, cleaning the screens and bar grate required workers in diving equipment to go below the surface of the water to clean out muck, vegetation and debris. Any decrease in water flow was also a decrease in dissolved oxygen, which posed a serious threat to the survival of the trout.

Harvest Rake screens ensure dependable debris removal, reduce labor costs and adhere to environmental regulations In 2023, the hatchery installed two Duperon® Harvest Rake screens to replace the older generation manual screens. The Harvest Rake screens collect debris upstream from the hatchery and deposit it on a

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WATER QUALITY

conveyor belt, which automatically returns it to the river downstream of the hatchery. This process allows the hatchery to remain debris-free while minimizing impact on the natural debris flow of the river. With the previous system, debris collection and offloading back into the river were all done manually. The Harvest Rake is specifically designed to manage high volumes of aquatic vegetation and is an especially good solution for sites that have side currents, backflow or channel turbulence. As an automated system, the Harvest Rake is reducing labor requirements for the hatchery. The setup includes speed control that can be adjusted for large debris and above-average flow conditions, such as after a large rainfall event. The installation at Jim Hinkle also includes a rear spray bar that ensures the conveyer is always clear and ready to accept debris from the rake. The Arkansas Game and Fish Commission required environmentally responsible equipment that would not disrupt the existing wildlife upstream or downstream of the hatchery, while also ensuring that mechanical equipment would not expose natural wildlife to hazardous chemicals. The Duperon Harvest Rake met all environmental compliance requirements.

Harvest Rake proved its worth during a recent flood On July 13, 2023, a major rainfall event caused flooding and a three-foot rise in the Spring River near Mammoth Spring in three hours. Had the previous system still been in place, hatchery manager BJ Vandiver would have

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had to call in at least two workers for “flood duty,” which, in this case, would have lasted all night long, as the river crested at around 11:00 PM. These workers would have spent the night manually removing debris from the screens to ensure that water kept flowing into the hatchery. Once the flood had passed, Vandiver estimates it would have taken at least a week to clean out the screens and remove all flood debris from the intake area in order to return to optimal flow rates that ensure trout survivability. For the Harvest Rake, however, the flood was no match. Vandiver said he reported to the hatchery to check on the equipment and was relieved to see the Harvest Rake dutifully and easily removing large amounts and large pieces of debris from the screens while allowing the river water to continue flowing safely into the hatchery. Not only did he not have to call in additional workers; he himself was able to return home. “With the Harvest Rake, the screening of the river is no longer something I have to worry about,” said Vandiver. “I don’t worry about it getting clogged up, I don’t worry about a large log damaging it, and I don’t worry about losing fish during a heavy rain.” References available on request.

More information: Steve Dill Mechanical Engineer Duperon Corporation E: sdill@duperon.com

Mark Hickok Regional Manager Duperon Corporation E: mhickok@duperon.com

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