Fisheries | Biology for Grade 12 PDF Download

Fisheries

- Fishes & other aquatic animals are reared and caught for food which is rich in protein vit A & D

- Pisciculture is rearing catching & management of fishes.

Pisciculture

- Culture fishery is the raising of fishes in tanks & ponds.

- Capture fishery is management of catching of fish without actually raising them.

- The per capita consumption of fish in India is estimated at 1.52 kg/ yr.

- India is at present the 6th foremost sea food producing nations in the world.

Blue Revolution is an effort to increase fish yield in India.

Cultivable species. of fresh water fishes -

* Indigenous species *

1. Labeo rohita (Rohu) – most common carp

2. Labeo calbasu (Calbasu)

3. Catla catla (Catla)

4. Wallage attu (Malli) 

5. Clarias betrachus (Magar)

6. Mystus singhala (Singhara)

7. Heteropneustes heteropneusts (Singhi)

8. Channa (Murrels) 

Exotic sps. 

- Cyprinus carpio (Common carp)

- Ctenopharyngodon idella (grass carp)

- Hypopthalmicthys molitrix (chinese carp/silver carp) 

- Osphronemus goramy (gaurami)

- Tilapia mossambica

Marine fishes -

1. Hilsa (Hilsa) - Coastal India

2. Aluitheronema (Salmon) - East & west coast

3. Sardinella (Sardine) - West & south coast

4. Harpodon (bombay duck) - Coastal Maharashtra

5. Stomaleous (pomphret) - Indopacific coast

6. Anguilla ( Eel), Mackerel

7. Chanos chanos (Milk fish)

8. Mugil (grey mullet)

* For efficient utilization of different type of food in the pond it is necessary to cultivate 2 or 3 types of fishes together. This is called composite or mixed farming

The major carps catla, rohu & Mrigal form a satisfactory combination in the ratio of 3 : 3 : 4. Selection of cultivable fish species is an important aspect of fish culture. Culturable fishes should have a high food value (both in quantity and quality), high reproductive and growth rates, higher disease resistance capacity, tolerance against the environmental fluctuations, an easy acceptance towards natural and artificial food and should be well compatible to the other fishes present in the pond or the aquatic habitat.

The above criteria are fulfilled only by  a few species of fishes, which are called as major carps. Therefore, the culture of these fishes are practiced in India at a large scale. At present three main species of the indigenous carps in India are included as the category of major carps. The three species are- Labio rohita, Catla catla and Cirrhinus mrigala. These species along with certain exotic carp species are cultured together in a  fish pond. This technique is called composite fish culture. An appropriate ratio among the individuals of various species is observed at the time of stocking the pond with fishes.

Important Steps of Fish culture

The major steps followed in the fish culture practice are briefly described in following lines

(i) In the beginning of the culture programme, a suitable site for  the establishment of a fish farm, is selected in  accordance to the standard criteria. a number of ponds of different types are then constructed and a dependable source of water is ensured to supply water into the nursery ponds, rearing or raising ponds and stocking ponds. The size, shape and depth of water in these ponds differ from each other.

(ii) Fishery ponds are usually Treated with lime to maintain an appropriate pH of pond water, Organic and inorganic manure and fertilizers are supplied in the pond to encourage the growth of planktons and other organisms that serve as natural food for fishes (this is called fertilization of pond). It is quite essential to remove the harmful aquatic weeds, predatory fishes and the harmful insects from the pond before introducing fish seed into the pond.

(iii) Fish seed is procured from the natural breeding places of fishes or may be collected from rivers during monsoon season.

(iv) In order to obtain pure seed of the desirable fish species, healthy males and females of a superior fish species are selected. These are then induced to breed artificially by (Hypophysation) giving in them the injections of pituitary extract (containing FSH or LH) or of a synthetic hormone like human chorionic gonadotropins (HCG). This stimulates females for spawning and the males to emit milt (containing sperms) on the ova to fertilize them.

(v) The fertilized eggs from the breeding pond are collected and transferred into hatcheries or hatching pits where they hatch to give rise to small hatchlings or sac fry.

(vi) The Juvenile sac fry are now transferred from the hatcheries into nursery ponds, where they develop into fry. These fry by feeding on zooplanktons and phytoplanktons, present in nursery ponds, grow in size and change into fingerlings. Fry are also fed by artificial food.

(vii) The fingerlings in next step, are transferred into rearing or raising ponds (this is called thinning), where they feed on both natural and artificial food. In rearing ponds, the fingerlings grow upto a size of 15-20 cm long. Now these are transferred into stocking ponds.

(viii) In the stocking pond the fingerlings soon become adult and attain table size (edible size) in about 6-9 months. These are given adequate food in these ponds and due care is given to protect them from diseases and other hazardous agents.

(ix) When the fish in pond have attained a suitable table size, the fishes are captured by using fish gears like hooks and lines, drag net, gill net , cast nest. This is called harvesting. These fishes are then taken to landing centres from where they are disposed off by selling into market. Our country has sufficient water resources including thousands  of the ponds in rural areas, These ponds may be used for fish culture together with the piggery, duck rearing, goat. which this along with providing employment to rural people, may also be an additional source of income.(Integrated fish culture) Certain premier institutes in India viz., Central Inland Capture Fisheries Research Institute (CICFRI), Barrackpore (W.B.); Central Marine Fisheries Research institute (CMFRI), Kochi (Kerala); Central Institute of Fresh water Aquaculture (CIFA), Bhubaneshwar (Orissa) and many other institutes, are continuously engaged in the research and extension studies in  the field of fisheries to make it more beneficial.

By-Product of fishing industry :-

1. Isin glass : It is a high grade collagen produced from air bladder or swim bladder of certain fishes like cat fishes & carps. The is in glass prepared in Russia is of best quality.

2. Fish oil –

– Dry oil is obtained from Salmon & Hersing.

– Semi dry oil from carps. Liver oil contains vitamin A, D, E & C.

3. Fish meal – It is prepared from wastes of fish oil. Wastes of cod industry is called "White fish meal". It contains Calcium (5.36%) phospholipeds (3.42%) and iodine. for younger animals it has proved to be a good nutritive diet.

4. Fish protein : Used in preparation of ice cream, pharmaceuticals, paints, varnishes, textile, paper and cosmetus.

5. Fish flour :- It is highly nutritive food and prepared by solvent extraction process easily digested by infants of 3-4 months.

6. Fish skin – of some fishes like shark & rays are used for covering card cases, jewel boxes, scab-boards etc. The skin of cod salmon and other fishes are also tanned and converted into leather.