WBCHSE HS Fisheries key terms

Farming of aquatic organisms such as fish, prawns and molluscs under controlled or semi-controlled conditions, where stocking, feeding and harvesting are managed by humans to raise production above what natural waters would yield.

Harvesting of naturally occurring fish and other aquatic animals from rivers, estuaries, lakes and the sea, where recruitment is not controlled by humans and the yield depends on wild stocks.

Polyculture of compatible species with different feeding habits - surface, column and bottom feeders - stocked together in one pond so that food at every level is used and yield per unit area rises.

Integrated system in which fish are reared in rice fields using the standing water of the plot; fish eat weeds, insects and bottom organisms while their droppings fertilise the field, giving two harvests from one land area.

Farming practice in which a poultry shed is built over or beside a pond so that droppings and spilled feed fall directly into the water, fertilising it and meeting part of the feed requirement of the stocked fish.

Number of fish or seed of a given size released per unit area or volume of water, usually expressed per hectare or per cubic metre; it governs growth rate, survival and final yield.

Sexually mature male and female fish selected and kept under good nutrition and water quality for breeding, either by natural spawning or induced breeding, in order to produce quality seed.

Technique of injecting hormones or pituitary extract into mature broodfish held in captivity so that they spawn at a chosen time, because natural spawning is inhibited under confined pond conditions.

Induced breeding method in which an extract of pituitary gland, usually taken from a donor major carp, is injected into the broodfish to trigger ovulation in females and spermiation in males.

Manual collection of eggs or milt by gently pressing the abdomen of a ripe broodfish from front to vent; eggs are stripped into a container and milt mixed in for fertilisation.

Rectangular fine-mesh net enclosure hung in a pond with its top above the water line, used to hold broodfish and to incubate fertilised eggs until hatchlings become free-swimming.

Newly hatched fish larva about three to five days old that has absorbed most of its yolk sac and begun taking external food; the earliest stage sold by a hatchery.

Successive seed stages: fry are roughly 20–25 mm long at 15–20 days of age, while fingerlings are 80–100 mm at two to three months, after rearing in nursery and rearing ponds.

Small shallow pond of about 0.02–0.1 hectare, carefully dried, limed and manured, used to raise spawn to fry over two to three weeks with abundant fine plankton and no predators.

Pond of about 0.1–0.5 hectare in which fry are grown to fingerling size over two to three months with supplementary feeding and periodic manuring before stocking into grow-out ponds.

Standard shorthand recording the number of hard and soft rays in each fin, for example D 3/15, P 1/16, used together with meristic counts to describe and identify a fish species.

Thin rounded overlapping scale with concentric growth rings called circuli and no spines, typical of carps and many soft-rayed fishes; the rings are read to estimate age and growth.

Row of pore-bearing scales running along the flank from head to tail, holding sense organs that detect water movement and vibration; its scale count is a standard identification character.

Concentration of oxygen gas dissolved in pond water, expressed in milligrams per litre; it is the most critical water quality factor, and most carps need more than 4 mg/L to feed and grow well.

Application of calcium carbonate or calcium hydroxide to pond soil and water to raise alkalinity and pH, improve soil texture and destroy fish pathogens and parasites before stocking.

Toxic fraction of total ammonia in water, whose share rises sharply with pH and temperature; even 0.1 mg/L can stress fish, damage gills and reduce feeding and growth.

Adding organic or inorganic nutrients to pond water to stimulate growth of plankton, the natural food of fish, so that production increases without a matching rise in expenditure on formulated feed.

Depth at which a black-and-white disc lowered into water disappears from view; a simple field index of plankton density and turbidity, with 25–40 cm regarded as good for carp ponds.

Kilograms of feed consumed divided by kilograms of fish weight gained; a lower value means better feed efficiency and is a key indicator of feed quality and farm profitability.

Feed given in addition to natural pond food, made from rice bran, oil cake, fish meal and similar ingredients, to support higher stocking densities and faster growth than plankton alone can sustain.

Calculating and mixing feed ingredients in fixed proportions so that the protein, energy, vitamin and mineral needs of fish at a particular stage are met at the lowest possible cost.

Plankton, algae, aquatic weeds, insects and bottom organisms that develop in a pond and are eaten by fish; they form the base of pond production and are managed through manuring and liming.

All preventive measures taken against disease on a fish farm - good water quality, balanced feeding, screened seed, disinfection of ponds and equipment - so that outbreaks are avoided rather than treated.

Fungal disease of freshwater and brackishwater fish, common in West Bengal in winter, marked by red spots and deep necrotic ulcers, caused by Aphanomyces invadans and often spreading after cold spells.

Bacterial disease caused by Aeromonas hydrophila and related species, producing skin lesions, fin rot, abdominal swelling and internal haemorrhages, usually triggered by stress and poor water quality.

Fungal infection of damaged skin and eggs by Saprolegnia species, appearing as white cotton-like tufts; it invades injuries and dead tissue and spreads quickly in crowded, unhygienic hatchery conditions.

Passive vertical net of thin nylon or monofilament mesh set in water with floats and sinkers, which entangles fish behind the gill cover; mesh size makes it a strongly size-selective gear.

Portion of a catch that is not the target species or size, including juveniles and non-commercial animals, discarded or landed at low value; a central concern in judging gear selectivity.

Chilling freshly harvested fish with crushed or flake ice in insulated boxes or holds to bring the temperature near 0 °C, slowing bacterial growth and enzyme action during transport and marketing.

Unbroken series of refrigerated handling steps - chilling at harvest, insulated storage, refrigerated transport and cold storage - that keeps fish at low temperature from pond to consumer.

Processing raw fish into products such as fillets, fish sticks, smoked or dried fish, paste or pickle, which fetch a higher price and keep longer than whole fresh fish sold in bulk.

Total discounted benefits divided by total discounted costs of an aquaculture enterprise; a ratio above one shows that the project returns more than it consumes over its working life.

Process of carrying research-based advice on pond management, seed, feed, health and marketing to fish farmers through field visits, demonstrations, farmer groups and training so that practices improve.