WBCHSE HS Fisheries cheat sheet

Capture fisheries take self-renewing wild stocks from rivers, estuaries and seas; culture fisheries (aquaculture) raise owned stock under managed conditions. Inland aquaculture dominates West Bengal's output.

India ranks second in the world in total fish production and second in aquaculture after China; inland freshwater aquaculture supplies the largest share of national output.

West Bengal is the leading producer of carp seed (spawn, fry, fingerling) in India and one of the top fish-producing states, with inland pond culture outweighing marine capture.

Sector weight: fisheries contribute roughly 1% of India's gross value added, about 6-7% of agricultural GVA, and support the livelihoods of more than 14 million people.

Intensity scale: extensive (no feed, low density, natural food only) -> semi-intensive (manuring plus supplementary feed) -> intensive (complete pellet feed, aeration, high density, high risk).

Water-type classification: freshwater ponds and tanks; brackishwater farms in the Sundarban belt at about 5-30 ppt salinity; marine cages and sea farming along the coast.

Life stages: egg -> spawn (5-8 mm) -> fry (10-20 mm) -> fingerling (75-100 mm) -> yearling; stunting results when fry are held too long at very high density.

Core terminology: plankton (phyto- and zooplankton), benthos (bottom-dwelling organisms), periphyton (film on submerged substrates), turbidity, carrying capacity, stocking density.

Hilsa (Tenualosa ilisha) is the state fish of West Bengal; it is an anadromous clupeid that migrates from the sea into the Hooghly for breeding.

Fin formula notation: D = dorsal, P = pectoral, V = pelvic, A = anal, C = caudal; Roman numerals are spines or hard rays and Arabic numerals are soft rays, e.g. D 3/14.

Scale types: cycloid (rohu, catla and most freshwater cyprinids), ctenoid (perch), placoid (sharks, rays), ganoid (gars); circuli and radii on scales give age and growth estimates.

Lateral line scale count (written L.l. 40-44) plus fin ray counts and gill raker counts are the standard meristic characters used in species identification.

Indian major carps: Catla catla - upturned mouth, no barbels, surface feeder; Labeo rohita - terminal mouth, one pair of short maxillary barbels, column feeder; Cirrhinus mrigala - inferior mouth, bottom detritus feeder.

Exotic carps used in polyculture: Hypophthalmichthys molitrix (silver carp, surface phytoplankton filter feeder), Ctenopharyngodon idella (grass carp, macrophyte feeder), Cyprinus carpio (common carp, bottom omnivore with two pairs of barbels).

Brackishwater species of the region: Lates calcarifer (bhetki), Mugil cephalus and Liza parsia (mullets), Penaeus monodon (bagda), Litopenaeus vannamei, Macrobrachium rosenbergii (golda), Scylla serrata (mud crab).

Air-breathing fishes - Clarias, Heteropneustes, Anabas, Channa - tolerate very low dissolved oxygen and are poor pond-mates for carps at high density because they are predatory or compete for feed.

Adipose fin is present in catfishes (Pangasius, Mystus, Wallago) and absent in cyprinids; the caudal fin of teleosts is typically homocercal.

Gill rakers are long, numerous and close-set in plankton feeders such as catla and silver carp, and short and sparse in carnivores such as Wallago and Channa.

Site criteria: soil with about 15-20% clay for water retention, gentle slope allowing gravity drainage, perennial water source, road access; avoid sandy-gravelly porous soils and steep hillsides.

Standard pond sizes: nursery 0.02-0.05 ha with 1-1.5 m depth; rearing 0.1-0.2 ha with 1.5-2 m; grow-out/stocking 0.4-1.0 ha with 2-2.5 m.

Shape rectangular with length:breadth about 3:1; dyke inner side slope 1:1.5 to 1:2; freeboard of 0.5-1 m above maximum water level.

Liming: agricultural lime (CaCO3) at 200-500 kg/ha/yr for soil pH 6.5-7.5; raise to about 1,000 kg/ha when soil pH falls below 5.5; quicklime (CaO) at 200-300 kg/ha for heavy organic bottoms.

Fertilization: cattle dung 10,000-15,000 kg/ha/yr, or urea 100-150 kg/ha plus single super phosphate 100-150 kg/ha, always applied in split doses to maintain a green bloom.

Dissolved oxygen: above 5 mg/L optimum, stress below 3 mg/L, mortality below 1 mg/L; DO peaks in late afternoon from photosynthesis and reaches its minimum just before dawn.

pH: 6.5-8.5 is optimal; heavy blooms cause a wide afternoon rise above 9, while pH below 5 depresses growth and indicates a lime requirement.

Ammonia: unionized NH3 is the toxic form and its share of total ammonia rises steeply with pH above 8 and temperature above 30 C; keep NH3 below 0.1 mg/L and total ammonia nitrogen below about 1 mg/L.

Alkalinity of 50-200 mg/L as CaCO3 and total hardness above 50 mg/L buffer pH and stabilise plankton; Secchi disc transparency of 30-40 cm indicates a healthy bloom.

Hypophysation: pituitary gland of a mature donor major carp is homogenised and injected intramuscularly; glands are preserved in absolute alcohol; a priming dose of 0.2-0.5 mg/kg precedes the resolving dose of 2-4 mg/kg in females.

Synthetic inducers: Ovaprim (salmon GnRH analogue with dopamine antagonist domperidone) at 0.3-0.5 ml/kg for females and about half for males; WOVA-FH and Ovatide are equivalents; HCG is used at 1,000-3,000 IU/kg.

Latency period from the final injection to spawning is roughly 6-12 hours at 26-28 C; it is shortest in mrigal and longest in catla.

Sexing major carps: males feel rough on the pectoral fin and operculum due to breeding tubercles and ooze milt on gentle pressure; females are smooth with a swollen, soft abdomen and reddish vent.

Hatchery components: brood stock pond, spawning pool or hapa, incubation/hatching tanks, spawn collection chamber and nursery ponds; eggs hatch in about 15-20 hours at 26-28 C.

Nursery pond preparation: dry, plough, lime, then eradicate predatory fish, insects and weeds with mohua oil cake at 2,000-2,500 kg/ha or bleaching powder before manuring and stocking.

Stocking norms: spawn 3-5 million/ha in nursery for 3-5 days, fry 200,000-300,000/ha in rearing ponds, fingerlings 5,000-10,000/ha in grow-out ponds.

Brood stock management: maintain 1-2 kg fish at about 1,000-1,500 kg/ha, feed oil cake-rice bran plus cereal, and segregate the sexes before the breeding season to prevent uncontrolled spawning.

West Bengal is India's largest carp seed producer, with hatchery clusters around Naihati, Kalyani and Purba Medinipur supplying spawn and fry to other states.

Natural food chain in a fertilised pond: phytoplankton -> zooplankton (Brachionus, Moina, Daphnia, Cyclops) -> benthos (Chironomus, Tubifex) -> fish; liming and manuring can multiply natural food several fold.

Conventional supplementary feed is rice bran plus mustard or groundnut oil cake at about 1:1, fed at 3-5% of body weight daily for fingerlings and 2-3% for growers, reduced in winter.

Nutrient targets: carp fry need 35-40% crude protein, grow-out 25-30%; lipid 5-8%, carbohydrate 25-40%, plus 2-5% binder such as molasses, wheat flour or tapioca.

Pearson's square: when blending two ingredients to a target protein, parts of ingredient A = (target - CP of B) and parts of B = (CP of A - target).

FCR = total feed supplied (kg) / total fish biomass gained (kg); carp on supplementary feed typically show FCR 1.5-2.0; feed efficiency ratio is the reciprocal, 1/FCR.

Feeding schedule: 2-3 feeds daily at fixed points or check trays, with monthly sampling to recalculate biomass; suspend or cut feeding during low DO, disease outbreaks or sudden temperature drops.

On-farm feed preparation: sun-dry, grind, sieve, mix, add binder, pelletise and dry to below 10% moisture; store in a dry aerated place to prevent rancidity and aflatoxin formation.

Specific growth rate (%/day) = 100 x (ln Wt - ln W0) / number of days; use it to compare growth between treatments or ponds.

Uneaten feed consumes oxygen and releases ammonia as it decays, so overfeeding is a leading cause of water quality failure and disease.

Bacterial diseases: Aeromonas hydrophila (haemorrhagic septicaemia with red patches and dropsy), Flavobacterium columnare (columnaris, grey saddle lesions and frayed gills), Edwardsiella tarda, Pseudomonas and Streptococcus; Vibrio species dominate in brackishwater and shrimp.

Fungal and oomycete diseases: Saprolegnia (white cotton-wool tufts on skin and eggs), Branchiomyces (gill rot) and Aphanomyces invadans, the agent of epizootic ulcerative syndrome with deep winter ulcers.

Parasitic problems: Argulus (fish louse), Lernaea (anchor worm), Dactylogyrus and Gyrodactylus (gill flukes), Ichthyophthirius multifiliis (white spot), Trichodina and Bothriocephalus (tapeworm).

Viral diseases: koi herpesvirus and spring viraemia of carp in carp; white spot syndrome virus and infectious hypodermal and haematopoietic necrosis virus in shrimp; tilapia lake virus; there is no cure, so cull, quarantine and disinfect.

Water quality as disease driver: DO below 3 mg/L, unionized ammonia above 0.1 mg/L, nitrite accumulation, abrupt temperature change and crowding suppress immunity and trigger outbreaks.

Prophylaxis: dry and lime the pond bottom, screen inlet water, quarantine new stock, avoid overstocking, feed a balanced ration, remove dead fish promptly and disinfect nets and buckets.

Banned substances in food fish include chloramphenicol, nitrofurans and malachite green; only approved drugs should be used, under veterinary prescription, with a written record.

Approved antibacterial dosing: oxytetracycline 50-75 mg/kg biomass daily for 7-10 days with a 21-day withdrawal before harvest; florfenicol 10 mg/kg biomass for 10 days.

Bath and dip treatments: common salt 2-3% for a short dip or 0.5-1% prolonged, potassium permanganate 2-4 mg/L, formalin 250 mg/L for 30-60 minutes; test the dose on a few fish before treating the whole pond.

Composite fish culture uses six species in three non-competing niches: catla and silver carp at the surface, rohu and grass carp in the column, mrigal and common carp at the bottom.

A widely used stocking proportion per 10 fingerlings is catla 3, rohu 3, mrigal 1, silver carp 1, grass carp 1, common carp 1; raise grass carp numbers if submerged macrophytes are abundant.

Stocking density in grow-out ponds is 5,000-10,000 fingerlings/ha with an expected yield of 3,000-5,000 kg/ha/yr when manuring and supplementary feeding are combined.

Paddy-cum-fish culture: a refuge trench of about 25% of the field area, water depth 10-15 cm, stocking 5,000-10,000/ha of common carp, rohu or freshwater prawn, giving an extra 500-1,000 kg/ha while fish eat weeds, insects and snails.

Integration rates: poultry-fish 500-650 birds/ha (droppings of 40-50 birds manure 1 ha), duck-fish 200-300 ducks/ha, pig-fish 40-60 pigs/ha, cattle-fish 5-10 animals/ha.

Integrated systems need continuous DO monitoring and periodic water exchange because constant droppings raise ammonia and BOD; excess manure should be diverted away from the pond.

Grass carp at 1-2 fish per 100 m2 controls submerged weeds biologically, while silver carp filters and controls heavy algal blooms.

Harvest strategy: partial harvesting of table-size fish with gill nets from about month 6, followed by complete harvest by draining at month 10-12.

Gear groups: gill nets (set and drift), cast net, seine and drag nets, lift nets, traps, hook and line/longline, and trawl; each targets a particular habitat, depth and size class.

Gill net selection is governed by mesh size and hanging coefficient (about 0.5), which fixes mesh opening; statutory minimum mesh sizes protect juveniles and brood stock.

Cast net: a circular net with weighted perimeter and mesh of 10-25 mm, thrown over fish in shallow ponds and rivers for sampling and small-scale harvest.

Seine net: two long wings with a central bag encircle a shoal and are hauled ashore; it is the standard complete-harvest gear in ponds, often with a 20-30 mm cod-end.

Trawl: a conical bag dragged by a boat, used in the Hooghly estuary and coastal waters; bycatch reduction devices and turtle excluder devices cut non-target catch.

West Bengal craft: plank-built and dugout country boats, FRP boats with outboard motors and mechanised trawlers; boats must be registered and fishing licensed.

Gear maintenance: dry after every trip, remove debris and mud, mend tears with matching twine, apply preservative and store away from direct sun and rodents.

Hilsa in the Hooghly is taken mainly with drift gill nets, and fishing is legally banned during the peak breeding period to protect the brood stock.

Kill and chill quickly: bleed, gut or gill, wash in clean potable water and ice at once; fish to ice at about 1:1 in insulated boxes holds flesh near 0 C.

Cold chain options: box icing, chilled seawater at about -1 C, slurry ice and refrigerated seawater for short storage, then frozen storage at -18 C or colder for long storage.

Spoilage indices: onset and resolution of rigor mortis, TVB-N above about 30-35 mg/100 g indicating spoilage, K value, rising pH, ammonia odour and softening of the belly wall.

Drying: moisture must fall below 15-20% for safe storage; salting (dry or brine) followed by sun drying is traditional for Bombay duck along the West Bengal coast.

Smoking: hot smoking at 70-80 C cooks and dries the flesh, while cold smoking at 25-30 C adds flavour and requires a prior salt cure to be safe.

Value addition: fish pickle, surimi and fish balls, fish protein concentrate, omega-3 rich fish oil, chitosan from shrimp shell, fish silage and fish meal from processing waste.

Marketing channel: fisher -> aratdar or commission agent -> wholesaler -> retailer -> consumer; each link takes a margin, so the fisher's share of the consumer rupee is often only about 50-60%.

Quality compliance: FSSAI licence and standards, HACCP-based processing, traceability and cold chain records; fresh fish is GST-exempt while several processed fishery products attract 5% GST.

Price determinants: species, size grade, freshness, the day's landing volume, festival demand (hilsa prices rise before Durga Puja) and distance and transport cost to the market.

Feasibility sequence: market study -> site and technical plan -> capital and operating cost estimate -> financial appraisal using NPV, benefit-cost ratio, IRR, payback period and break-even point.

BCR = present value of benefits / present value of costs; the project is viable when BCR exceeds 1, IRR exceeds the bank lending rate, and payback is shorter than the loan tenure.

Cost classification: fixed costs (land, pond construction, pump, aerator, shed) versus variable costs (seed, feed, lime, fertilizer, labour, electricity, drugs, fuel).

Pradhan Mantri Matsya Sampada Yojana (2020, outlay about Rs 20,050 crore) supports pond development, hatcheries, cold chain and marketing, with a higher subsidy share for SC/ST and women beneficiaries.

Credit channels: Kisan Credit Card for fishers and farmers, NABARD refinance, bank term loans, Fish Farmers Development Agencies and fishery cooperative societies; pond lease and insurance improve eligibility.

Insurance: group accident cover for fishers and aquaculture stock cover for ponds, with premium partly subsidised under government schemes.

Extension methods: individual (farm visit, office call), group (method demonstration, field day, training, aqua club) and mass (radio, television, leaflet, SMS, Kisan Call Centre 1800-180-1551).

Diffusion of innovation follows awareness -> interest -> evaluation -> trial -> adoption, with innovators, early adopters, early and late majority and laggards in that order.

Enterprise records: daily pond diary, seed and feed registers, cash book and cost of production per kg, from which gross margin and net return are computed.