In this issue:

High-health postlarvae a prerequisite for sustainability of the Indian shrimp industry. Broodstock and all-female scampi grow out ponds in south India. Genetically modified fish and potential applications. Rainbow trout farming in hill terraces of Nepal. Sugar industry by-products as plankton boosters and yield enhancers in carp culture. Growth and production of Penaeus monodon in low saline culture systems. Poor households raise prawns for export. Marine fish marketing in Bangladesh.

‘Spawn’ is the name for the young fish about three days old that are available from hatcheries. Sometimes these young fish are also called hatchlings. The spawn of catla, rohu and mrigal is about 6-8 mm long. At this stage, the ‘yolk sac’ is absorbed, the mouth opened and the fins fully developed. Spawn are reared intensively, first to the ‘fry’ size and then to the ‘fingerling’ size. All the three stages are marketed and collectively called ‘seed’.

The “fast fingerling system” can produce advanced fingerlings about two months earlier than they are normally available from fish farms.  The farmer uses just one pond for continuous growing until fingerling size is reached, and fewer fish are stocked. A farmer with a small, seasonal pond can produce fingerlings in one month. These can then be sold for a high price because everyone wants fingerlings as early as possible.

The fingerling rearing pond, like the nursery pond, should be free from weeds and predators. Submerged weeds and predators are killed by mahua oilcake, which then acts as a good fertiliser. If there are no weeds, to kill predators and competitors quickly you can just add 100 kg of urea followed 24 hours later by 200 kg of fresh bleaching powder for a 1-ha area of a 1-m deep pond.

In watersheds, medium irrigation projects can be useful for aquaculture even though these water bodies are many times larger than ponds, and are basically built for irrigation or water storage. However, the full potential of these water bodies is not yet realised. Net pens or cages can be used to rear fingerlings in such environments.