Hybrid African cat¢sh fry were acclimated for 14 days. A 70-day feeding experiment involving sixteen 38% crude protein diet treatments of four inorganic phosphorus (P) sources (monosodium phosphate, monopotassium phosphate, monocalcium phosphate (MCP), dicalcium phosphate (DCP)), four levels of P (0.04%, 0.06%, 0.08%, 1.2%) and three replicates of each diet followed. A non-P-supplemented diet and a puri¢ed diet (controls) were additionally fed. Gross e⁄ciency of food conversion (GEFC), daily rate of growth (DRG), tissue ash, tissue phosphorus (TP), tissue calcium (Ca) and Ca:P ratio of the ¢sh were measured weekly. These parameters varied signi¢cantly (Po0.01) among the (a) 18 test diets, (b) inorganic P sources and (c) duration. Monocalcium phosphatesupplemented diets resulted in better response to GEFC, DRG, TP and Ca than other P-supplemented diet while the Ca:P ratio was best exhibited by ¢sh fed the DCP diet. The ¢sh fed the control diets had better GEFC, DRG, TP and Ca than the P-supplemented diets probably because of nearer to optimum available P in these diets. In conclusion, supplementation with 0.6% MCP produced comparatively better growth, feed conversion and mineral deposition in the fry than other inorganic P sources.

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The effects of exposing Heterobranchus bidorsalis juveniles (14.08 ± 0.12 g) to dif erent concentrations of Bonny-light crude oil (BLCO) on amylase and cretinine kinase activities were studied The exposure of the f sh to 1.00, 2.00, 4 00, 8.00 ml L-1 BLCO and a control for 4 days toxicity period indicated that the signi icant increases (P < 0.01) in the serum amylase (SRA) and the hepatic cytosolic amylase (HCA) activities in the fish were BLCO concentrations dependent. Reduced SRA and HCA activities noticed within the first 14 days o the recovery period implied that the removal o the oil po lutant from the ambient water chemistry probably lowered the pressure on the blood serum and liver amylase enzyme to catalyse the metabolism o the inges ed carbohydrates. Sign icant increases (P < 0.05) in the serum cretinine kinase (SRCK) and the hepatic cytosolic cretinine kinase (HCCK) activities in the fish also followed the pattern shown by the SRA and the HCA activities. The increased SRA, HCA, SRCK and HCCK activities in the blood serum and liver of the fish were indications o a shi t in the carbohydrate metabolism due to crude oil exposure.

Variations in the proximate compositions of three age groups of Heterobranchus bidorsalis exposed to graded concentrations of Bonny-light crude oil (BLCO) were investigated in the laboratory. The sh were exposed to 1.00, 2.00, 4.00 and 8.00 ml L fi f i l f f .-1 concentrations of BLCO for 4 days (toxicity) and 42 days (recovery) periods. Signi icant decreases (P < 0.05) in the crude protein (CP), ether extract (EE), ash (AS) and dry matter (DM) contents of the juven le (JV), the yearling (YRL) and the adult (AD) fish were BLCO-concentration dependent. Lower CP values in the adult fish than in the juveniles or the yearlings implies that the crude oil compounds might have dep eted the quantity o protein faster in the adults than in the juveniles or the yearlings. Signi icant decreases (P < 0 05) in the EE content of the fish muscle could be attributed to the harmful effects of petroleum-related aromatic compound (ACs) on animals. These ACs might have caused decreases in the muscle triglycerides of the total lipid (EE) content of the three age groups of the fish. Significant increases (P < 0.05) in the nitrogen free extract (NFE) of the fish muscle might have been due to the high energy demand imposed on the fish as a positive survival value under the condition of crude oil stress.