Acute toxicity bioassay of the organophosphate pesticide chlorpyrifos ethyl on the fingerlings of Clarias gariepinus was evaluated to determine its effect on the survival, body morphology and the lethal concentration (LC 50). Following a preliminary bioassay in mg/l concentration which showed 100% mortality, fish were exposed to three replicate serial concentrations of 0.5, 1.0, 2.0 and 4.0 μg/l for 96 h. As soon as fish were transferred to the toxicant there was corresponding abnormal behaviour, characterized by restlessness uncoordinated swimming, loss of equilibrium, increase in opercula beats and air gulping, indicating respiratory stress. The effect of the toxicant is concentration and time dependent. The lethal concentrations (LC 50) of chlorpyrifos ethyl on the fingerlings of Clarias gariepinus for 24,72 and 96 hr were 2.0,1.0 and 0.5 μ /l respectively. Toxicant exposed fish also showed pinkish coloration at the caudal peduncle (tail region) and the operculum indicating of haemorrhage or damage to the tissue, resulting from respiratory stress. In conclusion, fish farmers are advised to take adequate precaution to prevent excessive use of organic pesticides such as chlorpyri for ethyl because of the possible loss to fish production.
The effect of fermented and unfermented Mucuna (Mucuna pruriens utilis) seed on growth performance of the Nile Tilapia, Oreochromis niloticus (L.) Trewavas, was investigated in eight weeks feeding trial in concrete tanks. Three approximately isonitrogenous diets were fed to three sets of fingerlings of Oreochromis niloticus. Specific growth rate (SGR), average weight gain, (AWG), percentage weight gain (FWG), food conversion ratio (FCR) and protein efficiency ratio (PER) were not significantly different (P>0.05) from the control. However, crude protein, ash and nitrogen free extract of the carcass composition were significantly different (P>0.05). Fish weight ranged from L75+0.14 -5.60+089, 2.13±0.43 -5.67+1.46 and 1.45±0.12 -4.87±0.64 for Dl, D2 and D3 respectively. The average weight gains were 3.85g, 3.54g and 3.42g for Dl, D2 and D3 respectively. Average apparent food consumed is in the order D2 >D1 > D3. Fermented Mucuna seed diet (D2) has the highest food conversion ratio of 1.51 followed by the control diet 1.22 and 1.19 for D3. Diet 3 is the most cost effective of the three diets. D3 has the highest food efficiency (0.84) followed by Dl (0.82) and the least D2 (0.66). Results of this study appear to show that unfermented Mucuna diet can conveniently replace Soya bean based diet for feeding Oreochromis niloticus.
The invasion of mangroves forest by nypa palm is said to affect the ability of the mangroves to act as a spawning ground for fishes. It is thus hypothesized that nypa palm presence in mangrove forest will impact their fish spawning ability due to the reduction in plankton population. A total of four stations were chosen: station 1 (open water), Station 2 (nypa palm dominant), station 3 (Rhizophora and Avicennia dominant), Station 4 (Mixed forest). Results of water quality parameters include; pH (6.99 ± 0.16), temperature (28.20°C ± 0.05°C), DO (4.71 ± 0.18 mg/L), conductivity (19.52 ± 0.20 µm/s), salinity (10.76 ± 0.07 ppt) and TDS (13.45 ± 0.27 ppt). Mean values of the physico-chemical parameters were not significantly different from each other (P > 0.05). In all 737 zooplankton in eleven genera were collected. Copepoda dominated with 75.1%. Similarly, 4774 phytoplankton in six taxa were collected. Bacilliarophyceae dominated with 87.45%. Shannon Weiner index across the stations was highest in station 4 (0.36) and lowest in station 1 (0.33). Margalef's index was highest in stations 2, 3, and 4 (3.48) and lowest in station 1 (2.67). Pielou's index of evenness was highest in station 4 (0.099) and lowest in station 1 (0.089). The composition and abundance of plankton showed no significant difference across the four stations (P > 0.05). This implies that the presence of Nypa fruticans (Wurmb) did not have negative impact on the abundance and diversity of plankton.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.