Fishery and Aquaculture: Composite Culture and Pond Management
What this domain tests
Species identification and feeding habits, pond preparation and stocking, water quality, and freshwater and brackish-water culture systems, with attention to West Bengal's bheri and Sundarban prawn farming.
Core facts
- Indian major carps: catla (surface feeder), rohu (column feeder), mrigal (bottom feeder). Exotic carps - silver carp, grass carp, common carp - fill the same niches, which is why six-species composite culture uses the whole water column.
- Pond preparation: dry, remove weeds and predators, apply lime 200–250 kg/ha, then cow dung or poultry manure; fill and allow plankton to develop.
- Stocking density roughly 5,000–8,000 fingerlings per hectare, with a species ratio of about 4 : 3 : 2 : 1 for catla : rohu : mrigal : silver carp.
- Water quality: pH 6.5–8.5, dissolved oxygen above 5 mg/L, secchi depth about 30–40 cm.
- Prawns: bagda (Penaeus monodon) in brackish water, golda (Macrobrachium rosenbergii) in fresh water. EUS affects finfish; white spot syndrome virus hits shrimp.
Worked example
A 1 ha pond is to be stocked at 5,000 fingerlings using catla : rohu : mrigal : silver carp = 4 : 3 : 2 : 1, i.e. 10 parts. One part = 500 fish. Catla 2,000, rohu 1,500, mrigal 1,000, silver carp 500. Reasoning: total the ratio parts first, then divide the stocking number by the total.
Traps that cost marks
Calling rohu a surface feeder; mixing the ratio parts; quoting the agricultural lime dose for a pond; confusing WSSV with EUS.