Abstract
This study was carried out to evaluate the growth performance and some haematological functions of Clarias gariepinus fed different levels of crude protein under varying stocking densities. Fish of even sizes were randomly selected and stocked in plastic circular tanks (0.05 x 0.03 x 0.03 m) at three stocking densities of 10 fish/m3 (control), 15 fish/m3 and 20 fish/m3. The fish of each stocking density were fed either a diet containing 40% Crude protein (CP) or 45% CP with a feeding rate of 3% body weight twice daily. The experiment was replicated thrice and it lasted for 12 weeks during which haematological parameters and plasma biochemistry were measured. From this study, haemoglobin (Hb) and Red Blood Cell (RBC) slightly increased in all treatments but the variation was not significant in relation to protein level in the diets. Plasma glucose increased significantly (P<0.05) in relation to the stocking densities. The plasma protein showed insignificant variation in relation to the stocking density but the variation was more pronounced (P<0.05) at the lowest stocking density as the protein level in the diets varied. It can be concluded that enhancing feed quality especially protein level in the fish diet may ensure faster growth, stress reduction and improve health status of the fish. Key words: Crowding stress, haematological functions, Clarias gariepinus, diet quality.
Highlights
Environmental stress is an important factor responsible for limiting fish performance under aquaculture conditions (Ellis et al, 2002)
Result from this study showed that there is no variation in the RBCs level with increasing stocking density; the RBCs level increased significantly (P< 0.05) with increase in diet protein level
The Hb and Hcrt followed the same pattern as observed for the RBC in relation to the stocking density but did not show any appreciable reduction with increase in diet protein level
Summary
Environmental stress is an important factor responsible for limiting fish performance under aquaculture conditions (Ellis et al, 2002). Overcrowding is a common chronic stressor in aquaculture that can induce a prolonged elevation of cortisol levels, which may cause damaging consequences, and suppressed growth (Rowland et al, 2006). This effect has been attributed to factors such as decreased food consumption. The high stocking density imposes increased energy demands that require fish to cope with metabolic adjustments, such as changes of gluconeogenic and glucolytic activities. Under such conditions, food consumption is reduced; the extra expenditure energy has. Total protein content in blood plasma was determined colorimetrically according to Henry (1964)
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