Growth, Nutrient Utilization and Physico-Chemical Responses in the Monoculture of Juvenile Clarias Gariepinus to Increasing Stocking Density

Abstract

A ten (10) week feeding trial was undertaken to assess the growth performance and nutrient utilization of Juvenile Clarias gariepinus of average weight range 250gm — 300gm stocked under 5 different treatments (10 (trt1) 15 (trt2) 20 (trt3) 25 (trt4) and 30(trt5) Juvenile Clarias gariepinus/250 litre bowl (under laboratory conditions) with increasing stocking densities, along with monitoring the following physico-chemical factors (pH, Temperature (°C), Dissolved oxygen (DO) in mg/litre, Ammonia (p.p.m), Alkalinity (p.p.m) and dissolved carbon dioxide (C02 in mg/litre). The increasing stocking density caused a decrease in value of the final fish body crude protein Trt1 (75.18%)> Trt2 (73.9 > Trt3 (72.71%)> Trt4 (71.21%)>Trt5 (70.19%). A similar trend was followed in the specific growth rate (SGR) pattern decreasing from 0.20 (Trt1) to 0.015 (Trt5) Mean weight gain (MWG) from 6.94 (Trt1) to 3.03 (Trt5) protein efficiency ratio (PER) from 0.29 (Trt1) to 0.04 (Trt5), productive protein value (PPV) from 0.24 (Trt1) to 0.04 (Trt5) and Net protein utilization (NPU) from 32.25 (Trt1) to 19.28 (Trt5). However the food conversion ratio (FCR) kept increasing from treatment (Tit1) (88.46) to 662.31 (Trt5) with increasing stocking density. This assertion is confirmed with the positive FCR correlation coefficient r=1.2964 while the other growth and nutrient utilization parameters had negative correlations respectively. Also the measured physicochemical factors in the study showed significant responses (P < 0.05) to increasing stocking density. The dissolved oxygen (DO) decreased with increasing stocking density, with a mean dissolved oxygen of 6.43mg/litre in treatment 5 containing 30 Juvenile Clarias gariepinus/250 litre bowl). Also the mean pH decreased from 7.73 (Trt1) to 6.58 (Trt5). Both the DO and pH values recorded were within the recommended tolerable ranges for all the treatments. However, an increasing pattern of variation was observed for ammonia increasing from 0.06ppm, (trt1 to 0.122p.p.m. (trt5), alkalinity increased from 30.70p.p.m. (Trt1) to 37.50p.p.m. (Trt5) and dissolved carbon dioxide increased from 9.27mg/litre (trt1) to 27.57°C (Trt4) to 12.18mg/litre (Trt5) while the mean water culture temperature also rose from 24.97°C (Trt 1) and 27.25°C for Trt5; this increase in temperature is also a result of the increasing stocking density of the juvenile Clarias gariepinus. All these increases (ammonia, alkalinity, CO2 and temperature) are indicators of increasing waste products with increasing number of fish in the bowls. This will eventually lead to fish mortalities (in the densely stocked treatments) and evidences of stunted growth alternatively is inevitable as a r’ of crowding of the fish in a limited space.