Assam ASSEB Higher Secondary Skill Subject Fishery Sciences flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Aquaculture

The controlled rearing of aquatic organisms such as fish, crustaceans, and molluscs in enclosed or managed water bodies, as opposed to harvesting wild stocks.

Composite fish culture

A polyculture system stocking several carp species with different feeding niches (surface, column, bottom) together in one pond to use all available natural food.

Beel fishery

A floodplain wetland fishery typical of Assam, where fish are harvested from natural depressions connected to rivers during floods; important for small indigenous species.

Fusiform body

A streamlined, spindle-shaped fish body form adapted for fast swimming in open water, as seen in carps and many pelagic species.

Heterocercal tail

A caudal fin in which the upper lobe is larger than the lower, as in sharks; it provides lift and is typical of elasmobranchs.

Annulus on scale

A growth ring on a fish scale formed during a season of slowed growth; counting annuli allows estimation of the fish's age.

Swim bladder

A gas-filled sac that regulates buoyancy; in physostomous fish it connects to the gut, in physoclistous fish it does not.

Counter-current exchange

Blood flow in gill lamellae runs opposite to water flow, maintaining a concentration gradient that maximizes oxygen uptake from water.

Ammonotelic excretion

Excretion of nitrogen mainly as ammonia, which diffuses across the gills; typical of most freshwater teleosts and requires abundant water.

Osmoregulation in teleosts

Marine fish drink water and excrete salt via gills; freshwater fish absorb salts and produce dilute urine to maintain internal osmotic balance.

Dissolved oxygen

Oxygen gas dissolved in water, measured in mg/L; levels above 5 mg/L support carp growth, while below 3 mg/L feeding and growth stop.

Secchi disc transparency

A measure of water clarity using a white disc lowered into the pond; 25–40 cm indicates a healthy plankton bloom.

Liming a pond

Applying lime (calcium carbonate or quicklime) to raise pH and alkalinity, improve buffering, and help eradicate predators and pathogens during pond preparation.

Feed conversion ratio

FCR equals feed supplied in kilograms divided by fish biomass gain in kilograms; lower values indicate more efficient feed use, typically 1.5–2.5 for carps.

Protein efficiency ratio

PER equals weight gain divided by protein fed; it measures how efficiently dietary protein is converted into fish flesh.

Supplementary feed

Feed given in addition to natural pond food to boost growth; carp feeds often mix rice bran, oil cake, and fish meal in defined proportions.

Induced breeding

Injection of hormones such as pituitary extract or synthetic analogues to trigger spawning in captive broodstock that would not breed naturally in ponds.

Hypophysation

Induced breeding using pituitary gland extract, given in two doses to females and one dose to males, to stimulate maturation and spawning.

Broodstock

Sexually mature male and female fish selected and maintained under good feeding and water quality for producing seed in a hatchery.

Nursery pond

A small, well-prepared pond used to rear spawn into fry for a few weeks before transfer to larger rearing ponds.

Saprolegniasis

A fungal infection causing cotton-wool-like growth on injured skin and eggs, usually secondary to handling injury; treated with salt or potassium permanganate baths.

Argulus

A fish louse, a crustacean ectoparasite that attaches to skin and gills, causing irritation and secondary infections; controlled with salt or chemical baths.

Disease triangle

The interaction of a susceptible host, a virulent pathogen, and an adverse environment; outbreaks usually require all three factors to coincide.

Gill net

A net that entangles fish by the gills; mesh size determines which size classes are caught, making it a selective fishing gear.

Cast net

A circular net thrown over the water and retrieved by a line; used in shallow ponds and rivers to catch small fish.

Beel fishing ban

A seasonal restriction on fishing during the monsoon breeding period, protecting spawning stocks and allowing juveniles to grow before harvest.

Ice chilling of fish

Cooling freshly caught fish to 0–4°C with ice slows enzymatic and bacterial spoilage, extending shelf life to several days before further processing.

TVB-N

Total volatile basic nitrogen, a chemical indicator of fish spoilage that rises as bacterial and enzymatic breakdown produces amines; high values indicate poor quality.

Fish silage

A value-added product made by acidifying minced fish waste so enzymes liquefy it; used as an ingredient in animal feed.

Benefit-cost ratio

BCR equals present value of benefits divided by present value of costs; a ratio above 1 indicates the enterprise is economically viable.

Break-even point

The output level at which total revenue equals total cost, calculated as fixed cost divided by contribution margin per unit.

Krishi Vigyan Kendra

A district-level farm science centre that provides extension services, training, and demonstrations to fish farmers and other agricultural producers.

Winkler titration

A titrimetric method for measuring dissolved oxygen in water; used in field practicals to assess pond suitability for fish culture.