Fish and fisheries Questions


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✍️ Write 2 cultured fish with scientific name.

➡️ Grass carp- Ctenopharyngodon idellus.

Dogfish- Squalus acanthias.

Eel- Anguilla spp.

Rohu- Labeo rohita.

✍️Case culture and pen culture advance n dis advantage.

➡️ Advantages:

○ The culture fishes obtained habitats of natural, physiological characteristics.

○ Constant supply of nutrients & planktnjonic feed organisms through the surrounding water body.

● Higher production & growth rate due to natural & restricted movements.

○ chances of water quality degradation.

● Supply of artificial food not required or if supplied the requirements is very low.

● Frequent monitoring of water quality not required.

● Harvesting is easy.

● Fishes have more market value compared to those culture fish ponds.


● Unfavorable water condition such as flood or drought may damage the pen culture.

● Over growth of aquatic weeds during winter season may create problem in the movement of fish as well as in netting operation.

● Low quality use of material may Caused under water damage of barrier causing

exit of culture fishes to natural water body.

● Accidental entry of predatory fish may Caused considerable damage to the juvenile fish.

✍️ Write about any two fish byproduct.

Fishes are one of the major source of essential proteins, fats, minerals, vitamins and for human and other piscivorous animals. In the fishery industry different parts such as head, scales, visceral Organs etc. Are produced as by-product because such parts are not consumed by humans. These are called fishery by-product and can be used to produce several important products with different market value.

Among them 2 byproduct are described below :

Fish flour: it is high quality fish meal where good quality raw material and hygienic manufacturing methods are used to produced flour of fish. It is used for human consumption as a suplimentary food. The bakery also uses to produce bread, biscuit and cakes from fish flour.

Fish silage: it is a semi solid jelly like substance produced from fresh fish in the European countries. It is nutritious containing protein, fatty acids and other components. It is obtained from formic acid or proteionic acid treatment or by fermentation. Fish silage is consumed by human or used to produced fish feed.

Fish glue: skin and fins of some fishes are used to produce glue. Fish glue in the manufacturing of postal stamps, book binding, paper boxing, shoe industry etc.

✍️Name any two fish Diseases and their agent.

Fishes are aquatic organisms where they encounters various infectious agents such as bacteria, fungi and sometimes parasitic organisms. Healthy fishes cultured in ideal aquatic parameters generally donot develop diseases. But sometimes these pathogens infect the fishes does affecting the productivity of cultured form.

Fish Diseases can be divided on the basis of causative pathogen.

Tail and Fin Rot Disease: it is a bacterial disease.

pathogen: Aeromonas, Pseudomonads, Mycobacterium and vibrio species.

Symptom and Damage: Initial damage in the fin or tail occurs due to mechanical reasons where the bacteria infect a whitish line or spot developes.

Branchiomycosis: it is a fungal disease.

pathogen: Branchiomyces.

Symptom and Damage: Decaying of gill occurs resulting haemorage, slime secretion increase, eye and body colour become pale.

✍️ Write about the mechanism of action of any one fish preservation methods.

➡️At present different methods are used to preserve the fish and fishery products based on the desirable end product properties. Most commonly used fish preservation methods are; chilling, freezing, curing (drying, salting and smoking), canning, marinating, boiling and fermentation. The other methods such as preservation by irradiation, freeze-drying, modified atmospheric packaging, retort pouch packaging are also used for preserving fish.

Canning and Retort pouch packaging:

The preservative effect in both the cases is mainly by subjecting the products in hermetically sealed containers / pouches, to high temperatures in order to bring the commercial sterility, where most of the microorganisms cannot survive, except highly heat stable spore formers. In this method the products are heated to high temperatures (121oC) for certain time with the intention of achieving commercial sterility to avoid the risk of pathogens and toxins, mainly Clostridium botulinum, which is a high heat resistant spore forming and toxin producing bacteria occurs in canned foods.

✍️Type of scale of fish.

Scales are important Exoskeleton in fishes. They have been divided into two basic types placoid and non placoid. The former is derived partially from the epidermis and partly from the dermis. Eg. Elasmobranch. But the non placoid scales are derived from the dermis. Eg. Pleleos.

1.Placoid scales: Placoid scales or dermal denticles are commonly found in the shark. These are plate like scales. The disc like broad vessel plate is embedded in the dermis and the spine is projected out through the epidermis . The spine has has a covering of anamel like material known as vitro dentine. Vitro dentine is epidermal in origin and the dentine is dermal in origin.

2.Cycloid scales: This scales are found in curbs. These are smooth disc like scales more or less circular in outline. The three margin of the scales had characteristic ridges alternating with grooves. The ridges are in the firm of concentric rings. The central part of the scales is known as focus.v

3.Ctenoid Scales: Ctenoid scales are present in several pteleos. Eg. Anabus. The posterior margin of the scales is comb like or serrated. A nuclear central zone can be recognised in this Scales also which is called the focus of the scale.

4.Ganoid scales: These are diamond shaped scales. Ganoid scales are the characteristics of primitive forms eg. Stargeons boufins .The scales are boney plates transverse centrally by canals.

5.Cismoid scales: this Scales are found in the living and extinct (crosopterygeans) . The external layer is thin and anamal like known as vitro dentine. Below these layer there is the layer of dentine like material the cosmine.

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