Growth performance of hybrid catfish (Heterobranchus bidorsalis (♀) x Clarias gariepinus (♂)) at various stocking densities in varied culture tanks

Stocking density effect of Heterobranchus bidorsalis (Š) and Clarias gariepinus (‰) hybrid juveniles stocked at densities of 7, 14 and 21 catfishes m-2 in three varied culture tanks (concrete, metal and plastic) were studied for 20 weeks. Total length and weight of catfish juveniles were recorded every fortnight. Plastic tanks with stocking density of 7catfishes m-2 had the best weight gain (4.89 } 6.81 g) while the least weight gain (1.39 } 2.16 g) was recorded in concrete tank with stocking density of 21 catfishes m-2. There was significant difference between stocking density of 7 catfishes m-2 (4.13 } 5.38 g) and 21 catfishes m-2 (1.82 } 2.26 g) (P < 0.05). There was no significant difference inspecific growth rate, feed efficiency and condition factor of catfishes in all culture tanks and stocking densities. The best total length of 12.23 } 5.22 cm was obtained in concrete tank with stocking density of 7 catfish m-2. The least mean total length (9.44 } 4.04 cm) was recorded in plastic tank with stocking density of 21 catfishes m-2. The effect of stocking density on total length was significant between stocking densities of 7 catfishes m-2 (11.85 } 5.52 cm) and 21 catfishes m-2 (9.54 } 4.01 cm) (P < 0.05)

Larvicidal effects of leaf, bark and nutshell of Anacardium occidentale on the larvae of Anopheles gambiae in Ebonyi State, Nigeria

Comparative analysis of the larvicidal properties of aqueous extracts of leaves, bark and nutshell of Anacardium occidentale L. (Cashew) were evaluated on the larvae of Anopheles gambiae. Three concentrations of 10/100ml, 20/100ml and 30/100ml each of leaf, bark and nutshell were prepared in three replicates. The treatments were exposed to two durations of thirty minutes and one hour. After thirty minutes of treatment, the mean mortalities were 53%, 68% and 56% for leaf, 64%, 71% and 57% for bark and 53%, 68% and 58% for nutshell, while the mean mortalities after one hour of exposure were 68%, 70% and 93% for leaf, 84%, 93% and 97% for bark and 61%, 68% and 73% for nutshell. Analysis of variance (ANOVA) showed that at thirty minutes of exposure, there were no significant difference (P<0.05) between concentrations and the percentage mortality, but it was highly significant (P<0.01) after 1 hour of exposure. Quantities phytochemical analysis revealed the presence of tannin, oxalate, stearic acid, glucoronic acid and glutamic acid in the leaf, bark and nutshell extracts

Preliminary evaluation of some aspects of the ecology (growth pattern, condition factor and reproductive biology) of African pike, Hepsetus odoe (Bloch 1794), in Lake Eleiyele, Ibadan, Nigeria

Abstract A preliminary investigation of length-weight relationship, condition factor and reproductive ecology of African pike fish, Hepsetus odoe, was conducted between June to August 2010 in Lake Eleiyele. A total of 90 samples of the fish species were caught by fishermen using gill nets. The results obtained showed that fish species had isometric growth pattern (contrary to negative allometry expected) with the growth exponent, b value of 2.64, that is not statistically different from 3 and with high statistical power of 0.866 when tested. The mean condition factor, K, was found to be 2.6, indicating that the fish species were in good condition in the study area. For reproductive biology, mean fecundity and gonadosomatic index were found to be 1349 eggs and 3.53% respectively. This study was necessary to fill the knowledge gap and provide information for management and conservation of the investigated species in the lake system. This study recommended that further research needs to be conducted because the sampling was carried out in the rainy season period and within a quarter of a year