The relative lethal and sublethal toxicity of cassava wastewater effluents from a local food factory were investigated on Clarias gariepinus fingerlings using a renewable static bioassay. The physico-chemical characteristics of the cassava wastewater effluents showed a number of deviations from the standards of the Federal Environmental Protection Agency (FEPA) on the guidelines for effluent discharges. Considering the pollutants of the effluent, cyanide (CN) is suspected to be primarily responsible for the toxicity, although synergistic effect of other pollutants cannot be ruled out. At each exposure, in the two tests, the test-organisms showed signs of serious stress, swimming pattern changed and mortality increased over relatively small increase in concentration. The LC50 for lethal and sublethal tests were 0.024 mg1 -1 and 0.0064 mg1 -1 , respectively. The differences observed in the mortalities and bioconcentration of metals in fish muscles of varying concentrations were significant (p<0.05). It is suggested that deposition of cassava wastewaters into aquatic environments may impair the natural population size while the consumption of fish from such environment is deleterious.

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Background: Fish have been at high risk of atrazine toxicity. Comparative atrazine toxicity on

Dietary habits of the up side-down Mochokid catfish, Synodontis membranaceus were investigated for 24 months (April 2002-March 2004, in Jebba lake, Nigeria) using frequency of occurrence, numerical, gravimetric and index of relative importance (RI) methods. The fish is euryphagus and feeds more at night. RI values indicate that 10 of the 16 food items were major diet components. The main five food categories are detritus (10.64 %), Aspatharia (9.08 %), plant parts (8.85 %), seeds (8.61 %) and Spirogyra (8.43 %), while the 5 less prominent food categories were gastropods (7.05 %), insect appendages (6.88 %), copepods (6.31 %), adult Povilla adusta (5.89 %) and coleoptera larvae (5.36 %). The remaining six food items, dragon flies, P. adusta larvae, chironomid larvae, Daphnia, water mites and fish scales had RI values considerably under 5 %. The prominence of detritus in the diet indicated that the fish is a bottom or benthic feeder. The wide variability in food supply enables S. membranaceus to maintain its overwhelming prominence in Jebba lake, and its euryphagus habit makes it suited for pond culture. Rev. Biol. Trop. 56 (2): 931-936. Epub 2008 June 30.

Background Pollution arising from the noxiousness of palm oil mill effluent (POME) has become a serious threat to aquatic biotas. However, a paucity of information exists on fish response to POME-mediated oxidative stress, lipid peroxidation, haemato-biochemical, enzymatic and ionic changes. This study, therefore, evaluates the effects of 28-day exposure of Heteroclarias, a hybrid catfish, to POME. Juvenile Heteroclarias (n = 350, average weight: 11.90 ± 0.70 g and average length: 9.04 ± 0.71 cm) were exposed to sublethal concentrations (0-control, 4.00, 8.00 and 12.00 mg/l) of POME to determine its effects on red blood cells (RBC), haemoglobin (HB), packed cell volume (PCV), white blood cells (WBC), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC) and mean cell volume (MCV). The activities of alanine aminotransaminase (ALT), aspartate aminotransaminase (AST), lactate dehydrogenase (LDH), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and the levels of malondialdehyde (MDA), calcium (Ca+), potassium (K+), magnesium (Mg2+) and sodium (Na+) ions were also assayed in the gill and liver. Results Exposure to POME caused significant (p < 0.05) concentration-dependent decrease in RBC, HB, PCV, MCV, MCH and MCHC values, whereas a significant (p < 0.05) concentration-dependent increase in WBC was observed in POME-exposed fish compared to the control. ALT, AST, LDH, GPx, SOD and CAT activities in the gill and liver significantly (p < 0.05) increased in a concentration-dependent manner. MDA level significantly (p < 0.05) increased in the gill relative to control, while in the liver it was insignificantly different. Both tissues exhibited an increase in Ca+, K+, Mg2+ and Na+ levels at the highest toxicant concentration with a rise of 77.93, 38.46, 109.54 and 41.99% recorded for the electrolytes in the gill and 79.17, 26.92, 55.48 and 38.78% in the liver above the control value, respectively. The levels of all the electrolytes except K+ were higher in the gill than the liver and were in the order: Na+ > K+ > Mg+ > Ca2+ in both tissues. Conclusions These results may be used as a suitable tool for pollution assessment and policy formulation to mitigate the discharge of untreated POME into aquatic ecosystems and their impacts on resident organisms.

Background Atrazine has impacted negatively on fish by inducing significant alterations in their haematological, biochemical and histological parameters. Mitigating such alterations to enhance fish survival becomes pertinent. Unfortunately, readily available and eco-friendly remedies are scarce. The study, therefore, investigated the potential ameliorative effects of dietary supplementation of aqueous Carica papaya and Mangifera indica leaf extracts on atrazine-induced toxicity and oxidative damage in the tissues of Clarias gariepinus. Fish (average weight: 10.57 ± 1.69 g, and average length: 10. 36 ± 1.26 cm) were randomly divided into six groups of ten samples each. Group I served as control and administered borehole water only, group II was exposed to 8.50 µg/l atrazine corresponding to ¼ of 96 h LC50, group III was treated with low (0.25 mg/g) concentration of each extract alone, group IV was exposed to 8.50 µg/l atrazine and treated with the low concentration of each extract, group V was administered with high (0.75 mg/g) concentration of each extract alone, and group VI was exposed to 8.50 µg/l atrazine and treated with the high concentration of each extract. The experiment spanned 28 days after which the haematological, biochemical and histopathological alterations were assayed. Results Atrazine intoxication significantly induced oxidative damage in the gill and liver, culminating into different histopathological disorders, decreased haematological parameters, increased serum, gill and liver levels of malondialdehyde and enzyme biomarkers (alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and acetylcholinesterase). On the other hand, atrazine exposure caused decreased levels of glucose, protein and superoxide dismutase in the tissues. Treatment with diets fortified with both extracts significantly increased all the decreased haematological parameters, reduced the serum levels of the elevated malondialdehyde and tissues enzyme biomarkers in a concentration-dependent manner. Biochemical parameters in the tissues were also improved with dietary supplementation of the extracts. Histopathological examination of both tissues showed ameliorating effects of both extracts in restoring the structural and functional integrity of each tissue. Conclusions These results suggest that the extracts have ameliorative potentials against atrazine-induced peroxidative injury in C. gariepinus. The utilisation of these extracts could enhance better health management practices, particularly in a rice-cum fish culture, where atrazine application is common.

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