Assam ASSEB Higher Secondary Skill Subject Fishery Sciences cheat sheet

Aquaculture is the controlled rearing of aquatic organisms; capture fishery is harvesting wild stocks. Assam's inland sector is dominated by pond and beel (floodplain wetland) fisheries.

Classification by salinity: freshwater (ponds, rivers), brackishwater (estuaries), marine (sea cages, coastal ponds).

Culture systems by intensity: extensive (no feed, low density), semi-intensive (supplementary feed, fertilization), intensive (formulated feed, aeration, high density).

Monoculture = one species; polyculture = multiple species with complementary feeding niches (e.g., surface, column, bottom feeders); composite fish culture in India typically uses 3 Indian major carps + 3 exotic carps.

Integrated fish farming links pond culture with piggery, poultry, duckery, or horticulture so wastes become pond inputs, reducing feed cost.

Cage and pen culture confine fish in enclosed water bodies; biofloc and recirculating aquaculture systems (RAS) allow high-density production with limited water exchange.

Capture-based aquaculture (ranching, ranching of seed) differs from true aquaculture because juveniles are collected from the wild rather than bred in captivity.

Key species groups in Assam: Indian major carps (catla, rohu, mrigal), exotic carps (silver, grass, common carp), air-breathing fishes (magur, singhi, koi), and small indigenous fishes.

Fish body form relates to habit: fusiform (fast swimmers), laterally compressed (reef dwellers), depressed (bottom dwellers), anguilliform (eel-like), and globiform.

Fins: paired (pectoral, pelvic) for steering and braking; median (dorsal, anal, caudal) for stability and propulsion. Caudal types: homocercal (symmetrical), heterocercal (shark-like), diphycercal (primitive).

Scales: cycloid and ctenoid (teleosts), placoid (elasmobranchs), ganoid (primitive). Scale rings (annuli) are used in age determination.

Mouth position indicates feeding niche: terminal (mid-water), superior/upturned (surface feeder), inferior/ventral (bottom feeder).

Gill structure: four pairs of holobranchs on arches, with primary and secondary lamellae providing a large respiratory surface.

Swim bladder (gas bladder) provides buoyancy; in physostomous fish it connects to the gut via the pneumatic duct, in physoclistous fish it does not.

Weberian apparatus in otophysan fishes links the swim bladder to the inner ear for sound detection.

Reproductive modes include oviparity, ovoviviparity, and viviparity; many freshwater species are seasonal breeders triggered by monsoon floods and temperature rise.

Counter-current gas exchange: blood in secondary lamellae flows opposite to water flow, maximizing oxygen uptake.

Heart is two-chambered (one atrium, one ventricle) with a sinus venosus and bulbus arteriosus; blood passes through gills before the systemic circuit (single circulation).

Osmotic strategy: marine teleosts drink water and excrete excess salt via gill chloride cells and small urine; freshwater teleosts absorb salts and excrete copious dilute urine.

Excretion is mainly ammonotelic: ammonia diffuses across gills; kidneys handle water balance and some urea/trimethylamine oxide.

Digestive tract in carnivores is short and stomach is prominent; herbivores/omnivores have longer guts and may lack a true stomach (cyprinids).

Hormones: pituitary gonadotropins control maturation; thyroid regulates metabolism; corpuscles of Stannius and ultimobranchial body regulate calcium.

Respiration rate and opercular movement increase with temperature, low dissolved oxygen, and stress; this is used as a field indicator of water quality.

Nervous system includes a well-developed lateral line for detecting water movement and low-frequency vibration.

Pond depth 1.5–2.0 m; pond area typically 0.2–1.0 ha for composite culture in Assam; bottom slope allows complete draining.

Dissolved oxygen should be above 5 mg/L; below 3 mg/L feeding and growth stop; below 1–2 mg/L fish gasp at surface (early morning) and mortality can follow.

pH optimum 6.5–8.5; liming with agricultural lime (CaCO3) or dolomite raises pH and alkalinity; quicklime (CaO) is used for pond preparation and eradication of predators.

Total alkalinity 50–200 mg/L as CaCO3 and total hardness above 50 mg/L support good plankton production.

Secchi disc transparency 25–40 cm indicates healthy plankton bloom; green water is desirable, blue-green scum or clear water is not.

Fertilization with organic (cow dung, poultry manure) and inorganic (urea, single super phosphate) inputs promotes natural food; avoid over-fertilization that triggers oxygen depletion.

Ammonia (unionized NH3) toxicity rises with high pH and temperature; keep total ammonia nitrogen low and monitor after heavy feeding.

Pond preparation sequence: drain and dry, remove weeds and predators, apply lime, fill water, then fertilize before stocking.

Crude protein requirement varies by species and stage: fry 35–45%, grow-out carp 25–30%, and higher for carnivorous species.

Feed ingredients: energy sources (rice bran, wheat bran, maize), protein sources (fish meal, soybean meal, groundnut oil cake, mustard oil cake), and minerals/vitamins.

Feed conversion ratio (FCR) = feed supplied (kg) / fish biomass gain (kg); lower FCR means better efficiency; typical carp FCR 1.5–2.5.

Protein efficiency ratio (PER) = weight gain / protein fed; net protein utilization and apparent digestibility coefficients measure protein quality.

Feeding rate is commonly 3–5% of body weight per day for fingerlings and 2–3% for grow-out fish, adjusted for temperature and natural food availability.

Feed form: mash, crumbles, pellets (sinking or floating); pellet size should match mouth gape; floating pellets allow observation of feeding response.

Feeding schedule: 2–3 times daily at fixed stations; avoid overfeeding because uneaten feed decomposes and depletes oxygen.

Essential amino acids (e.g., lysine, methionine) must be supplied; limiting amino acids reduce growth even when total protein is adequate.

Induced breeding uses pituitary gland extract (PG extract) or synthetic hormones (e.g., ovaprim, human chorionic gonadotropin) to trigger spawning in captive broodstock.

Hypophysation: donor pituitary from mature major carp is injected into the female in two doses (preservative and resolving dose), with a single dose for males.

Breeding hapa or circular hatchery: eggs are collected, incubated in hatching hapa or Chinese circular hatchery, and hatch in about 18–24 hours depending on temperature.

Sexual maturity in Indian major carps: catla 2–3 years, rohu 2–3 years, mrigal 1–2 years; breeding season coincides with monsoon (May–August in Assam).

Broodstock management: separate male and female ponds, feed with oil cake–rice bran mixture, maintain good water quality, and select healthy brooders.

Sex identification: males have rough pectoral fins and oozing milt; females have smooth pectoral fins and a swollen, soft abdomen.

Hatchery water quality: temperature 26–30°C, dissolved oxygen above 5 mg/L, and low ammonia; eggs need gentle water flow and no silt.

Seed rearing: spawn to fry in nursery ponds, fry to fingerling in rearing ponds, with density and feeding adjusted to stage.

Disease triangle: susceptible host + virulent pathogen + adverse environment; most pond outbreaks are triggered by water quality stress.

Bacterial diseases: hemorrhagic septicemia (Aeromonas), tail rot and fin rot, dropsy; treatment includes antibiotics only under veterinary guidance and improved water quality.

Fungal diseases: saprolegniasis (cotton wool growth) on injured skin and eggs; treat with salt or potassium permanganate baths.

Parasitic diseases: Argulus (fish louse), Lernaea (anchor worm), Dactylogyrus (gill fluke), and Ichthyophthirius (white spot); control with salt baths, formalin, or potassium permanganate.

Viral diseases have no direct cure; control by quarantine, screening, and disinfection. Koi herpesvirus and spring viraemia of carp are notifiable examples.

Diagnosis: observe behaviour (gasping, rubbing, lethargy), external lesions, gill colour, and wet mount microscopy of skin and gills.

Prevention: pond drying and liming, screening of seed, avoiding overstocking, maintaining dissolved oxygen, and quarantining new stock.

Drug withdrawal periods must be observed before harvest to avoid residues; record all treatments.

Gill nets entangle fish by the gills; mesh size determines the size of catch and thus selectivity.

Cast nets are thrown and retrieved; used in shallow ponds and rivers for small fish.

Drag nets and seine nets encircle and haul fish to shore; used in open water and pond harvesting.

Hooks and lines (longline, handline) are used for predatory and large fish; baited hooks target carnivores.

Traps and pots capture fish alive; fyke nets and bamboo traps are traditional in Assam floodplain fisheries.

Beels (floodplain wetlands) and rivers support capture fisheries; fishing bans during monsoon protect breeding stocks.

Electrofishing and explosives are destructive and illegal; they kill juveniles and damage habitat.

Gear selectivity and bycatch reduction are core management tools; minimum mesh size regulations protect juveniles.

Fish spoils rapidly due to high moisture, neutral pH, and enzymatic/ bacterial action; chilling to 0–4°C with ice extends shelf life to several days.

Preservation methods: icing, freezing, drying, salting, smoking, canning, and fermentation. Drying reduces moisture to about 15–20%.

Value-added products: fish pickle, fish balls, fish cutlet, fish sausage, dried fish, fish protein concentrate, fish oil, and fish silage.

Quality indicators: sensory evaluation (eyes, gills, flesh, odour), TVB-N (total volatile basic nitrogen), and microbial counts.

HACCP (Hazard Analysis Critical Control Points) and good manufacturing practices ensure food safety in processing units.

Marketing channels: producer → wholesaler → retailer → consumer; cooperatives and self-help groups shorten the chain and improve margins.

Cold chain infrastructure (ice plants, cold storage, refrigerated transport) is a key constraint in Assam's fish marketing.

Branding, packaging, and certification (e.g., organic, geographical indication) add value and market access.

Cost-benefit analysis: total revenue minus total cost; net profit = gross income − (fixed cost + variable cost).

Break-even point = fixed cost / (selling price per unit − variable cost per unit).

Benefit-cost ratio (BCR) = present value of benefits / present value of costs; a BCR above 1 indicates viability.

Payback period = initial investment / annual net cash inflow; shorter periods mean faster recovery.

Extension methods: individual contact (farm visits), group methods (demonstrations, field days), and mass media (radio, posters, mobile advisories).

Krishi Vigyan Kendras (KVKs), the Department of Fisheries, and NGOs are key extension providers in Assam.

Entrepreneurship support: credit via NABARD and banks, subsidies for pond construction, hatchery units, and cold storage.

Record keeping (input costs, stocking, harvest, sales) is essential for farm economics and access to credit.

Water quality testing: pH by pH meter or indicator paper; dissolved oxygen by Winkler titration; alkalinity and hardness by titration; ammonia by nesslerization or test kit.

Secchi disc measures transparency; a disc disappearing at 25–40 cm indicates a healthy bloom.

Plankton sampling with a plankton net and observation under a microscope; identify phytoplankton (e.g., Chlorella, Microcystis) and zooplankton (e.g., Daphnia, Cyclops).

Fish measurement: total length (snout to caudal tip), standard length (snout to caudal base), and weight; length-weight relationship W = aL^b.

Age determination by scale reading: count annuli and back-calculate length.

Hatchery practical: observe induced breeding, egg incubation, and spawn collection; record hatching rate.

Pond preparation practical: drying, liming, manuring, and stocking density calculation.

Field visit to a fish farm, beel, or market to observe production, harvesting, and marketing practices.