Aquatic Fish animal biology

Like any animal, a basic understanding of how fish function is necessary if one is to try to culture them. Fish are different to land animals as they have evolved to live in water, which makes movement, breathing, buoyancy and food or predator detection very different to that encountered on land. One of the most fundamental differences between fish and land animals is that the former are essentially

weightless in their environment and dependent on it for their temperature, being ‘cold-blooded’, and this means that they neither need food energy for fighting the force of gravity nor for keeping themselves warm, as do land animals like cows and sheep. This makes their conversion of feed into mass more efficient than with

land animals, given the right environmental conditions.

Biology of the species

  • Growth rate – Species that grow quickly reach market size in a shorter time. However, under similar conditions, higher-valued species may sometimes be more cost-effective to culture as compared to cheap, fast-growing species.
  • Feeding habits – The species being cultured must have dietary requirements that can be met by the pond and the Producing fish at a low cost relies on the fish using as much of the pond’s natural food as possible. If greater production is wanted, additional feeding will be required, but this adds to the expense of fish farming. For example, catfish require a high-protein diet which cannot alone be provided from the natural food in the pond.
  • Reproductive biology – It is usually best to choose a species that breeds easily and therefore produces many
  • Hardiness – The commonly cultured species are popular around the world mainly because they adapt well to being
  • Market – Many aquaculture businesses

that fail, do so because they did not check properly that there was an economic market for their fish.

  • Profitability – It is very important that a careful cost analysis is done concerning the costs of maintaining the ponds, buying the young fish, feeding them, and any other costs incurred while they Once all the costs have been worked out it is possible to calculate the minimum price that each fish can be sold for.

If at all possible, farmers should be encouraged

to start their ponds using a tested pond fish that is locally available and well-liked by people in the area. If the fish can grow in ponds and the farmer is able to sell the fish or use them for his/ her family, more or larger ponds could be built.

To decide which fish species are suitable for aquaculture in South Africa, we should look at case studies from other countries.

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