Objectives of Aquaculture

Having defined aquaculture, it is proper to state the objectives of aquaculture. These are:

1. Production of protein rich, nutritive, palatable and easy digestible human food benefiting the whole society through plentiful food supplies at low or reasonable cost;

2. Providing new species and strengthening stocks of existing fish in natural and man-made water-bodies through artificial recruitment and transplantation;

3. Production of sportfish and support of recreation fishing;

4. Production of bait-fish for commercial and sport fishery;

5. Production of ornamental fish for aesthetic appeal;

6. Recycling of organic waste of human and livestock origin;

7. Land and aquatic resources utilization: this constitutes the macro-economic point of view benefiting the whole society. It involves: a) maximum resource allocation to aquaculture and its optimal utilization; b) increasing standard of living by maximizing profitability; c) creation of production surplus for export (earning foreign exchange especially important to most developing countries);

8. Providing means of sustenance and earning livelihood and monetary profit through commercial and industrial aquaculture. This constitutes the micro-economic point of view benefiting the producer. In the case of small-scale producer, the objective is to maximize income by greatest possible difference between income and production cost. In the case of large scale producer, the objective is to maximize return of investment;

9. Production of industrial fish.

Fish flesh, on the average, contains: moisture and oil-80%; protein-15-20%; mineral matter – 1-2% and other constituents – 1%. Water content is known to vary with fat content.

Need for artificial recruitment has arisen in order to replace stocks decimated by: a) decline of water quality and destructive fishing (polluting, poisoning, dynamiting); b) barrier to migration caused by execution of river valley projects; c) overfishing.

From the global view point, the fish which have overwhelmingly dominated artificial recruitment are: a) Oncorhynchus, b) Acipenser, c) Salmo. Artificial recruitment of carp, tilapia and mullet are also important mostly in tropical and subtropical countries. Oncorhychus and Salmo transplants have contributed maximum to sport and recreational fishing. Production of livebait e.g. skipjack tuna is an example of bait production for commercial fishing. Some potential live-bait species are Tilapia mossambica, Dorosoma petenense, Engraulis japonicas, Sardinella malanure, several species of mullets and cyprinids. A wide variety of ornamental fish appeared such as sword tail; angel fish; Siamese fighter; goldfish and common carp. Production of industrial fish includes production for purpose of reduction to fishmeal or fertilizers. Seaweeds are cultured for marine colloids and pearl oysters for cultured pearls. As it is recognized that aquaculture provides protein-rich food, it should be pointed out that protein production through aquaculture is much more efficient than production in any other animal production.

Fish

Fish, any of a variety of cold-blooded, vertebrate animals found in the fresh and salt waters of the world. Living species range from the primitive, jawless lampreys and hagfishes through the carulaginous sharks, skates and rays to the abundant and diverse bony fishes.

Fishes are enormously varied in shape, size and colour. Their bodies are generally fusiform (tapered to each end) and they can range in length from 10 mm to more than 20 m. Most fishes that inhabit surface or midwater regions are streamlined or flattened side-to-side, while most bottom-dwellers are flattened top-to-bottom. Tropical species are often brightly coloured and others may have a drab appearance so as to blend in with their surrounding environment. Most fishes have paired fins and their skins are covered with either bony or toothlike (placoid) scales; some have bony plates embedded in the skin or lack scales. Respiration is generally through gills. Most bony fish have a swim bladder, a gas filled organ used to adjust swimming depth. In a few species the swim bladder has evolved into a lunglike respiratory organ, enabling these fishes to breathe air. Most fish reproduce by laying eggs, which may be fertilized externally or internally. Some species are hermaphroditic, although examples of fishes that are self-fertilizing are rare. A few fishes bear live young. The mortality rate of eggs and hatching is generally very high; only a few individuals reach adulthood out of a batch of hundreds or even millions of eggs. The central nervous system of fishes – the brain and spinal cord – controls body activity. Most fished have a well-developed sense of smell; the olfactory, or nasal organ is located on the dorsal surface of the snout. Many fishes have taste buds in their mouth cavities. Most can see well and experiments have shown that many fishes, especially those that swim near the surface, have colour vision. Hearing organs are located within the skull, on either side of the brain. The lateral line system, consisting of highly innervated fluid-filled canals that run the length of the body, detects vibrations in the water current. Fish first appeared 450 million years ago. Since that time they have evolved to fit almost all freshwater and saltwater habitats.