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Study was conducted to evaluate effects of feeding different dietary protein levels on haematological profile and leukocyte population of Clarias gariepinus using net-hapa system. Catfish fingerlings (mean weight 4.50± 0.01g) were randomly stocked at 20 fish per net-hapa (1m 3). Five experimental diets with crude protein of 40.00%, 42.50%, 45.00%, 47.50% and 50% were formulated and fed to the fish for 24 weeks. Blood samples were collected and examined for white blood cell (WBC), red blood cell (RBC), haemoglobin (HB), haematocrit (HCT) mean corpuscle volume (MCV) mean corpuscle haemoglobin (MCH) mean corpuscle haemoglobin concentration (MCHC), Platelet (PLT), leukocytes, lymphocytes, neutrophils, monocytes, eosinophils and basophils. Results revealed a reverse relationship between haematological indices of fish and dietary protein inclusion levels. The best WBC (207x10 3 count/μl), RBC (4.9x10 6 count/μl), Hb (19.0g/dl), HCT (41.0%), MCV (149.0fL), MCH (49.35pg), MCHC (40.6g/dl) and PLT (134.0x10 3 count/μl)) were presented in fish fed 40% protein diets. Results of leucocyte population did not follow any particular trend. A high positive correlation (r>0.9000; p<0.05) existed between the treatments in RBC, WBC, and Hb. The results conclude that 40% dietary protein inclusion is recommended for C. gariepinus for sound and healthy condition in floating net-hapa system.

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The plankton of Odot Stream, Niger Delta, Nigeria were investigated between June and August, (wet season) and October -December, 2014 (dry season) using standard analytical procedures. The data generated were subjected to descriptive statistics and community structure analysis. A total of 37 species of Phytoplankton belonging to four taxa were identified in ascending order as follows: Xanthophyceae (4.7%), Baccillariophyceae (20.19%), Cyanophyceae (36.34%) and Chlorophyceae (38.71%). Zooplankton belonging to 4 taxa were also identified in ascending order as follows; Cladocera (11%), Copepoda (11%), Larvae (26%), Rotifera (52%). Higher seasonal abundance among the families were recorded in dry season for Chlorophyceae (39.16±14.75), Cyanophyceae (21.83±6.50) and Xanthophyceae (10.66±5.81) while higher wet seasonal abundance were recorded for Baccillariophyceae (22.25±4.59) and Copepoda (0.58± 0.34). Chlorophyceae and Rotifera were found as the dominant group in this present study and indicated that Odot stream was highly productive (eutrophic), which could be attributed to high temperature due to the shallowness of the stream and its high exposure to sunlight. Excessive algal bloom should, therefore, be checked to prevent the stream from anoxia and poor water quality and shift in species composition and fish kill.

Acute toxicity effects of ethanol extract of Alchornea cordifolia leaf on Clarias gariepinus fingerlings was investigated over a 96hr exposure period as a potential organic piscicide. A static toxicity bioassay was performed after preliminary trial tests (range-finding test) were conducted. Five hundred (500) post-fingerlings of Clarias gariepinus were distributed randomly in duplicate concentrations. The test fishes were treated with concentrations of 1.31, 1.96, 2.97, 4.45 and 6.67 mg/1 of Alchornea cordifolia. Exposure to the plant toxicant caused visible behavioural changes which include erratic swimming, air gulping, discolouration, loss of body equilibrium, the settlement at the bottom and death. Mortality was recorded in some of the exposed fish while the LC50 lethal concentration of 2.138 mg/1 was established and safe concentration was established as 0.2138 mg/l. There were significant changes (p˃0.0.5) in the water quality parameters except for electrical conductivity, the unstable behaviour of the fish must have been as a result of irritation from the toxicant. Therefore, the use of A. cordifolia in fish harvesting should be regulated and not allowed to gain access unnecessarily into the aquatic ecosystem and regulatory bodies should maintain the safe concentration of 0.2138 mg/l.