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Studies on some aspects of the biology of Heterot s nilot cus in Anambra river were carried out for 22 months. Analysis of the stomach content of 546 species of H. niloticus in Anambra river established the preponderance o plantivorous crustacean, copepods and cladocera throughout the four maturation stages examined. Seasonal variations occurred in the dietary components of the fish. The length-weights relationship and the relative condition revealed that females had better condit on. The mean length and we ght were 94.5 ± 60 cm (29-167 cm) and 120 ± 21.8g (10-250g) respectively. A sex ratio of 1:0.8 (M: F) at Otuocha was more pronounced than at Ogurugu and Nsugbe. D gestive enzyme assays in the different gut regions (oesaphagus, stomach, pyloriccaeca, ileum and rectum) of H. niloticus showed an array of glycosidase (amylase, sucrase, malatase, lactase, cellulase); protease, (pepsin, trypsin, chymotrypsin) and l pases. The pattern of spread and relative activity of the enzymes is consistent with its planktophagous diet. Haematocrit values, haemoglobin concentrations, erythrocyte and leucocytes counts, mean cells haemoglobin concentrations, plasma protein, glucose, albumin and inorganic ion (sodium, chloride, calcium, potassium, magnesium, phosphorus) for H. niloticus were established. Correlations were found between some blood parameters and standard length.

Primextra is a commercial herbicide formulation generally used in agriculture for weed control. The present study was designed to investigate the oxidative stress biomarkers and biochemical responses in the tissues of Clarias gariepinus juvenile exposed to primextra. Fish were exposed to 0.24 and 0.47 mgL(-1) corresponding to 1/20 and 1/10th of 96 h LC50 of the herbicide. The liver and muscle tissues were sampled on day 1, 5, 10 and 15 and results showed concentration and time dependent significant increase (p < 0.05) in the values of lipid peroxidation, glutathione peroxidase, catalase and alkaline phosphatase in both tissues. A marked significant increase (p < 0.05) was observed in the values of aspartate aminotransferase, alanine aminotransferase and glucose in the liver while a mixed trend in their values were observed in the muscle. The values of superoxide dismutase and protein in both tissues were comparable to the control except on day 15 in the liver where the values significantly declined. The condition factor was not directly affected but values of hepatosomatic index were significantly reduced. The present findings revealed that primextra induced toxic stress even at sublethal concentrations resulting in alterations of the studied parameters which were more evident in the fish liver than in the muscle tissue.

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