No abstract

The hatchery facilities of a reputable fish farm in Abeokuta were used to carry out studies on the effects of different diets on the survival of African catfish Clarias gariepinus hatchlings. The larvae (1.8mg each) were distributed into the twelve feeding experiment apartments (1.7 m × 0.7 m x 0.5 m each) at 1,500 lavae/apartment. On the fourth day, feeding commenced with the experimental diets. The diets were fish meal (Danish) of 72% Crude Protein; baker's yeast (VAHINE); compounded feed (50% Crude Protein) and hen egg yolk. Each treatment was replicated thrice and feed fed to the larvae at 30% body weight twice daily for 30 days. All the experimental diets had no significant effects on the growth of the larvae to fingerling at P > 0.05. The mean fingerlings final weight (mg) was 1523.2 ±295, 1700.8 ± 686, 367.9 ± 118 and 1675.9 ± 1167 for fish meal, yeast, compounded feed and hen egg yolk respectively. The specific and relative growth rates of the larvae under all the treatments were also not significant (P > 0.05). Considering the growth parameters, the best performance was observed in fish fed diet 2 (yeast), closely followed by diet 4 (hen egg yolk), then diet 1 (fish meal) and least in fish fed diet 3 (compounded feed). The low survival rate observed in all the diets, Compounded feed (10%) > hen egg yolk (4.1%) > Fish meal(3.5%) > yeast(1.7%) could be attributed to the lack of sorting exercise carried out in the experiment.

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Improved Aquaculture Management Practices (LAMP) always lead to increase productivity, generate greater income, reduce poverty and improve livelihood. This study assessed the extent of the use of IAMP by fish farmers in the Western Zone of Lagos state ADP, Nigeria to describe level of usage of IAMP and examine the constraints faced by fish farmers in the use of IAMP The primary data were collected with the aid of structured interview guide, administered through personal interviews and observations to elicit information from 100 fish farmers using simple random sampling and purposive technique. Descriptive statistics was used to analysis the socio-economic characteristics, while budgetary analysis was used to determine the profitability and multiple regression analysis. Findings show that the mean age of the respondents was 42.6 years, 71.0% were male, 90.0% married, 63.0% secondary occupation and 84.81% were aware of IAMP On a daily basis, 87.0% of the respondents were involved in record keeping, 82.0% carried out general observation in the farm and used concrete tanks while site selection, tank construction, pond liming and use of drugs were done occasionally. Constraints faced by the respondents were high cost of inputs (88.0%), flooding (79.0%),. predators (71.0%), mortality (61.0%), pollution (61.0%), inadequate technical know-how (61.0%) and disease outbreak (58.0%). Respondents' household size (r = -0.202, p<0.05) and marital status (χ2= 61.082, P<005) were significantly associated with factors affecting the use of IAMP. There were significant differences between IAMP used and revenue generated (t =4.641.,p<0.05). In conclusion, adoption of IAMP leads to increase aquaculture productivity and changes of social status. Government should provide assistance in loan at low interest, appropriate land, grants, fish farm input at subsidized rate adequate marketing information and networking among fish farmers.

As from January 2010 The Israeli Journal of Aquaculture -Bamidgeh (IJA) will be published exclusively as an on-line Open Access (OA) quarterly accessible by all AquacultureHub (http://www.aquaculturehub.org) members and registered individuals and institutions. Please visit our website (http://siamb.org.il) for free registration form, further information and instructions.This transformation from a subscription printed version to an on-line OA journal, aims at supporting the concept that scientific peer-reviewed publications should be made available to all, including those with limited resources. The OA IJA does not enforce author or subscription fees and will endeavor to obtain alternative sources of income to support this policy for as long as possible.

The amount of naturally occurring radionuclide in Teak plantation was measured using gamma ray spectrometer RS-125. This device gave an in-situ measurement of radioactivity concentration of 40K, 232Th, 238U and dose rate. The data was taken in 20 locations, the overall mean dose rate (DR) is 47.8150 Gyh−1. The overall mean activity concentrations for 40K, 232Th, 238U are 456.1975 BqKg−1, 29.0245 BqKg−1 and 26.2080 BqKg−1 respectively. It was also observed that only the estimated outdoor dose rate D of 40K at study location L1 exceeded the world limit of 57nGyh−1. This could be due to its closeness to the university main gate with lots of possible interfering human activities around the gate area. However, further study on detailed geochemical investigation is required to reach at some conclusion. By comparing the mean values of the activity concentrations and their radiological risks with the several world standards, it can be concluded that the Teak plantation is highly rich in Potassium.

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Environmental enrichment (EE) improves the growth rate and welfare of some cultured fishes. However, most cultured fish species are raised in non-enriched housing conditions. Clarias gariepinus is an important commercial fish species, but little is known about the effect of EE on their welfare. This study examined the effect of different EE on the survival rate (SR), growth [mean weight gain (MWG), specific growth rate (SGR) and feed conversion ratio (FCR)], behavioral (feed response, aggressive acts and shoaling time) and physiological responses (blood glucose) of C. gariepinus. One hundred and twenty juveniles of C. gariepinus (31.65 ± 0.69 g) were randomly allocated at 10 fish/tank and subjected to either Plant Enriched (PE), Substratum Enriched (SE), Plant and Substratum Enriched (PSE) and Non-Enriched (NE) tanks in triplicates for 56-days. Behavioral acts were observed for 10 min twice daily, and glucose level in blood samples was evaluated. Data were checked for normality using the Shapiro-Wilk test before being analyzed with the Kruskal-Wallis test. SR and MWG were significantly higher in Clarias gariepinus exposed to SE, with no significant differences among PE, PSE and NE treatments. There was no significant difference between the SGR of PSE and NE. FCR was similar between treatments. The highest condition factor (k) was recorded in SE tanks. Duration of feed response was shorter in SE, but there was no significant difference between the feed response of C. gariepinus exposed to PE and PSE. C. gariepinus exposed to PE, SE and PSE displayed a similar frequency of aggressive acts. African catfish reared in NE (barren) tanks had the least duration of shoaling period. The experiment consistently found the highest and least glucose values in PSE and SE. In conclusion, environmentally enriched housing tanks with SE resulted in the best MWG with a reduced level of aggression in C. gariepinus under laboratory conditions. Thus, EE might be applicable to boost fish productivity on a commercial scale.