The following points highlight the seven main qualities that determine the suitability of species for aquaculture. The qualities are: 1. Rate of Growth and Production 2. Size and Age at First Maturity 3. Breeding 4. Adult Feed 5. Preference of Hardy and Disease Resistant Species 6. Influence of Species on Environment 7. Intensive and Semi-Intensive Cultures.
Quality # 1. Rate of Growth and Production:
The rate of growth and production under culture conditions is a major characteristic that determines the suitability of a species for aquaculture. Certain slow-growing species may be candidates for culture because of their high market value, but it is generally difficult to make their culture economical.
The use of heated water can definitely improve the growth rates of many species, but use of such a method has not yet proved commercially successful.
Quality # 2. Size and Age at First Maturity:
It is preferable to select those fishes which will reach marketable size before attaining first sexual maturity, as most of the feed would be used by them for somatic growth. Early maturity before reaching marketable size would obviously be a great handicap (example : Tilapia). However, early maturity would ensure easier availability of breeders for hatchery operations.
Quality # 3. Breeding:
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If breeding criteria are taken into account then species preferable for culture should consider the following :
(a) Seeds Available from the Wild:
In species where controlled breeding techniques under captive conditions have not been perfected, the aquaculturist would have to depend upon seed availability from the wild. This, however, proves to be an unreliable source in large scale farming because their abundance in nature depends upon a number of unpredictable factors.
Moreover, large scale collection of spawn and fry has resulted in conflict with commercial fishermen, who blame the aquaculturist for the decline in the catch. However, there is no scientific evidence for this point of view. So, it is advisable to select species that can be propagated in hatcheries.
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(b) To Culture a Species that can Breed under Captive Condition’s:
It is advisable to select species for aquaculture that can breed under captive conditions. This would enable production of adequate quantities of seed through hatchery production. If the selected species matures more than once a year, then it would be possible to have several crops of seed, if other conditions remain suitable.
(c) High Fecundity and Frequency of Spawning:
It would be advantageous if the selected species have high fecundity and greater frequency of spawning. However, small sized eggs and small sized larvae make hatching operations difficult. If the incubation period and larval cycle are shorter, then mortality of larva would be lower with greater hatching survivability.
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(d) Artificial Feed Acceptance of Larvae:
Rearing of live food is difficult and often expensive. Therefore, larvae that accepts artificial feed is easier to rare in hatcheries.
Quality # 4. Adult Feed:
Feeding may account for more than 50% of the total cost of production, and is, therefore, of prime concern in modern aquaculture.
(a) Culture of Herbivorous and Omnivorous Species:
Herbivorous and omnivorous species have been preferred for culture as they feed on natural food organisms in water. The growth of natural food can be increased through fertilisation and water management. The cost of feeding in such cases will be relatively low. Shorter the food chain, faster is the growth rate. So, herbivorous and omnivorous species are preferred for the production of low-priced products.
(b) Species Adopted to feeding with Artificial Food Stuff:
Feed efficiency in relation to growth and productivity is an important criteria. Some low trophic level feeders can sometimes be highly selective in their feeding habits. For example, some filter-feeders may require plankton of a particular size and shape, which sometimes may not be available in the impoundment.
So, the need to grow these species to market size within a limited season or period often makes it necessary to resort to artificial feeding. Also sometimes the natural feed may dwindle due to grazing. So, in such cases, species adopted to supplementary feeding with artificial foodstuffs is generally preferred.
(c) Culture of Carnivorous Specks :
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Carnivorous fishes require high protein diet which is more expensive and largely depends on local availability. However, the high feeding cost is compensated as most carnivorous species command high market price. Such species have greater export market and thus, attract substantial investments.
Quality # 5. Preference of Hardy and Disease Resistant Species:
In relatively poor and partially polluted water bodies, the temperature and oxygen concentrations can fluctuate, and deterioration of the water quality may occur unavoidably. In such unfavourable conditions, species that are hardy will obviously fare better. At the same time they should be resistant to diseases.
Quality # 6. Influence of Species on Environment:
Some species may have certain influence on the environment. For example, soil erosion may be caused due to the feeding habit of carps. Such species which upsets the ecological balance would need special protective measures, leading to higher cost of maintenance and environmental concern.
Quality # 7. Intensive and Semi-Intensive Cultures:
Intensive and semi-intensive cultures involve high stocking density, confined in a limited space, with water recirculation system and intensive feeding. Overcrowding may lead to an increase in transmission of diseases, cannibalism in the early stages and accumulation of waste products. Species that can withstand such environmental hazards are better candidates for aquaculture.
In the selection of species for culture, the economic considerations are more important to an aquaculturist than biological factors. The presence of proven technologies for culture along with economic viabilit-. acts as a guideline for investors and aquaculturists, in the selection of a species for culture.