EXPERT TOPIC
TIGER PRAWN
EXPERT TOPIC
Giant tiger prawn
by Rebecca Sherratt, Features Editor, International Aquafeed
The Giant tiger prawn (Penaeus monodon) is a prominent crustacean within the aquaculture industry, farmed in large numbers that are second only to the Whiteleg shrimp (Litopenaeus vannamei).
O
ne reason for the Giant tiger prawn’s widespread popularity is their adaptability and ease of farming. This particular shrimp can flourish in a wide range of salinities between 3-35ppt, although their optimal levels are between 15-25ppt and temperatures of between 28-33°C. Giant tiger prawns can be found across the globe, ranging from Southeastern Asia, the Pacific Ocean, Northern Australia and the Arabian Peninsula. Giant tiger prawns can be distinguished by their dark colouring. Their carapace and abdomen, banded with black and white, contrast the red, light blue or brown hue of their bodies. Giant tiger prawns can exceed sizes of 330mm and 33kg in weight, females typically exceeding males in size. Giant tiger prawns feed upon small crustaceans, molluscs and polychaete worms. Many wild subspecies of tiger prawns are nocturnal, emerging from the substrate under cover of darkness to search for food or to mate. Larvae will hatch offshore, before entering estuaries and swamps that serve as nursery grounds. Juvenile Giant tiger prawn will move into deeper waters upon maturation. Commercial farming of Giant tiger prawns began in the late 1980s and has seen a gradual increase with only slight fluctuations in farming numbers throughout the years. In 1990, 289,799 tonnes (t) of Giant tiger prawns were farmed for aquaculture globally, which increased to 630,984t in 2000 and 701,081t in 2016.
Optimal feeding solutions
In order for farmers to achieve optimal yield in their harvests, much research has been conducted to discover nutrients that best promote shrimp growth. Giant tiger prawns are typically farmed in ponds, wherein their natural diet of copepods and polychaetes can be supplemented with pelleted feeds to achieve a nutritionally balanced diet. In a study conducted by Tacon in 2002, an estimated 75-80 percent of all farmed shrimp are fed with industrially compounded aquafeeds. The most efficient feed for Giant tiger prawns must be rich in 10 essential amino acids; methionine, histidine, tryptophan, isoleucine, arginine, valine, threonine, lysine and phenylalanine. Of these ten, methionine, arginine and lysine can prove expensive to make readily available, which is where cystine can prove useful as an alternative to methionine and tyrosine as a partial substitute for phenylalanine. Fatty acids are also vital for the growth of Giant tiger prawns. Four specific fatty acids are deemed vital for the species; docosahexaenoic, linolenic, eicosapentaenoic and linoleic acids. In a 1976 study by Guary et al, it was demonstrated that Giant tiger prawns will exhibit improved growth rates when fed lipids from marine sources, rather than from vegetable oil. Other fatty acids such as arachidonic acid do not necessarily promote optimised growth, but have been deemed advantageous in ensuring proper maturation. Soybeans have become a popular ingredient within shrimp feed as a source of phospholipids. Lecithin has been proven to be an effective growth-promoter in shrimp, which soybeans provide in abundance as 52 | July 2020 - International Aquafeed