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How much is enough when feeding your fish?
W
hen feeding your fish, one of the most important factors to consider is your feeding strategy. Feeding costs can be as much as 30 to 80% of the total production cost of an aquaculture enterprise, depending on the type of production system and intensity of production. Choosing the appropriate feeding strategy is therefore important to help minimise feeding costs while maintaining optimal growth.
The selection of a feeding strategy may be influenced by the following: Water temperature Water temperatures below or above the recommended optimal range for a species will decrease the feeding rate. Photo period The photo period or the time exposed to light can affect the growth, feeding efficiency, locomotor activity and sexual maturation of aquaculture species. Generally, longer photo periods lead to increased somatic growth due to increased feed intake. Water quality Nutrients and organic matter from excess feeds and faeces can cause rapid deterioration of water quality. Poor water quality, can adversely affect the fish. Fish size and age The quantity of
feed
per
mass
unit will decrease as the mass per fish increases. Juveniles require higher feeding rates compared to older fish. Fish stocking density The higher the biomass of a system, the higher the absolute feeding requirements. Natural water productivity In a pond system, the natural water productivity refers to the quantity of live or natural feed available to the fish. The higher the productivity, the lower the feeding requirements of the fish. Feed moisture content The higher the moisture content of the diet, the lower the concentration of the nutrients, and consequently the higher the feeding rate should be. Feed energy content This has the most significant influence on the feeding rate. Fish generally eat to satisfy their energy requirements. The energy concentration of the diet will therefore directly determine the quantity of “other nutrients” the fish consumes. Thus, the importance of a balanced (energy to protein) diet is clear. Aside from the factors that can directly affect the fish, the following should also be considered when selecting your feeding strategy:
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• Market value of the species being produced, • Availability of labour, training requirements and cost, • Financial resources (for example cash flow, access to finance), • Cost of production inputs (fertiliser, feed, electricity, water, fuel, et cetera), • Type of production system (cage system, raceways, dam, et cetera) and • Water availability and replacement rate. In terms of selecting your feeding strategy, there are several strategies you can employ. Two common strategies that can be used are ad-libitum feeding or feeding at a predetermined feeding level. It is important to note that, depending on your situation, you will often find a balance between these two strategies that suits your needs. Ad-libitum feeding: Ad-lib feeding entails the feeding of fish until all the fish are satisfied. The ability of the person feeding the fish to judge when the fish have had enough is very important. Experience, a high standard of management and good supervision are important for optimal production. Although ad-lib feeding is a well-established strategy to feed fish, there are some risks associated with it. Bad management of ad-lib feeding can lead to overfeeding. This reduces the resulting percentage meat weight of the 9
