IU S A G N A P F O
O C I R O T R UE P IN
., McGee, Ph.D by Michael V. Rico Lajas, Puerto
he Asian catfish Pangasius, Pangasianodon hypophthalmus is recognised as a leading aquaculture food fish on world markets. The commercial culture of Pangasius was developed in the mid 1990â€™s in Vietnam and quickly expanded to production levels of nearly one million tons per year. Other countries including Thailand, Cambodia, Myanmar, Indonesia, Philippines, Bangladesh and India have adapted Pangasius as part of their aquaculture production. Pangasius can be successfully cultured in most tropical regions of the world however countries in the Western Hemisphere have been slow to embrace Pangasius aquaculture, in part, due to the lack of practical knowledge of the species food requirements during the larval and fry stages. Pangasius are a riverine species and require specific environmental conditions under which to reproduce naturally. All Pangasius reared in aquaculture are reproduced by hormone inductions. The eggs and milt are stripped from the fish and artificially propagated under hatchery conditions. At a temperature of 28 C Pangasius eggs hatch in about 24 hours and the larvae become free swimming almost immediately afterwards. The larvae are small (3 mm) and require further development for at least 48 to 60 hours prior to first feeding. Pangasius larvae are pelagic, swimming through the water column and normally feeding on small zooplankton that they randomly encounter.
Under culture conditions Pangasius larvae are moved about 24 hours after hatching to a nursery pond that has been prepared for this purpose. Larvae are stocked at a density of 400 to 600/m3 and are dependent on natural zooplankton of the correct size, type and abundance to sustain the larvae during at least the first seven days of life when they do not feed on prepared diets. The larvae will consume newly hatched Artemia if reared in hatchery tanks however densities of the larvae must be reduced to around 10 larvae per litre to avoid cannibalism which at the early life stages can significantly reduce survival. Caribe Fisheries began reproducing pangasius in 2002 and has continued to evaluate procedures to improve spawning success and larval survival. It was noticed that survival of Pangasius from larvae to fingerlings in nursery pond varied widely between ponds. To better understand the factors that lead to these disparate results a study was conducted from May to September 2014. Observations were made daily on all ponds used for pangasius fingerling production to document the zooplankton populations, presence of predators and the condition and survival of the larvae during the first seven days after stocking. Although the study was conducted under commercial farm conditions the general methods used and the results obtained are considered useful in indicating conditions which can lead to improved production of pangasius from the larval to fingerling stages. Earthen ponds used in the study were approximately 20 X 40 metres and 1 metre deep. The ponds were covered with 2 cm bird netting to prevent adult dragonflies from laying eggs in the
26 | May | June 2016 - International Aquafeed