Pollution of inland water ways is largely as a result of human activities along the river banks. Some heavy metals concentrations of River Argungu were evaluated due to its close proximity to the town. The study lasted for 12 months (March, 2014-February, 2015) using Energy Dispersive X-ray Fluorescence (ED-XRF) Analysis. Nickel and copper were highest during the month of July with mean values of 1.02±0.02 and 1.81±0.23 mg LG 1 , respectively, lead and chromium were highest during the month of September with mean values of 13.12±0.18 and 0.14±0.05 mg LG 1 , respectively. The Mean±SD of eight heavy metals assessed indicated that, nickel, iron, lead and cadmium detected were observed to be higher than the permissible limit (nickel 0.02, iron 0.30, lead 0.01 and cadmium 0.003 mg LG 1) throughout the study period. Zinc was however, lower than the permissible limit of World Health Organization (WHO) throughout the period of the study. Most of the highest concentrations of heavy metals observed were at the onset and during the rainy season. The high concentrations of some heavy metals observed in the river could be as a result of human activities mostly concentrated at the river banks and runoff during the rainy season. This study infers that, some fish species could be threaten as a result of the high concentrations of most of the heavy metals, thus the need for an efficient and sustainable fisheries management to control human activities along the river bank.

No abstract

The experiment was conducted to assess the growth performance and feed utilization of Clarias gariepinus under the feeding frequencies of T1 (twice/day), T2 (thrice/day), and T3 (four times/day) at 3% BWD per day over a period of 56 days. A total of 180 fingerlings with average weight of 2.39±0.19g and average length of 5.02±1.04cm were stocked at 15 fish per plastic container of 35 litres capacity. The highest weight gain recorded at the end of the experiment was 7.39±0.19g in (T3) and the lowest was 5.35±0.31g in (T1). The highest specific growth rate (SGR%) value of 1.19±0.02 was recorded in (T3) and the lowest 1.01±0.03 was recorded in (T1). T3 recorded the highest FCR value of 1.88±1.37, while the lowest value of 8.34±2.12 was obtained in (T1). Therefore, Treatment 3 yielded the best performance in terms of WG, SGR, and FCR and can be recommended for enhanced growth performance and optimum feed utilization.

The growth parameters and age for the fish species from the lake (O. niloticus, S. galilaeus and B. bayad) were computed through interpretation of marks found on their Opercula bones which were then fitted into Vonbertallanfy growth model. Their asymptotic length (L∞) ranged from 175mm-520nm. The growth performance index Ф' ranged from 3.6622-4.9420 and K value from 0.10-0.35. O. niloticus L∞, K and Ф' values ranged from 175mm-192.5mm, 0.15-0.25, 3.6622-3.9668 and were found to live up to 7 + years in the lake. The values of S. galilaeus ranged from 200mm-240mm, 0.12-0.17 and 3.8211-3.8222 and living up to 5 + while B. bayad had a range of 500mm-520mm, 0.10-0.35, 4.4320-4.9420 and lives up to 6+ in the lake. All the growth parameters for the fish species were fitted into the Vonbertallanfy growth model. L t =L∞ (i-ek (t-t o)

The experiment was conducted to determine the length weight relationship and condition factor of Clariasgariepinus and Oreochromisniloticus in five different stocking combinations for a period of twelve weeks from 17 th July-9 th October, 2009. A total of 1,509 juveniles of C. gariepinus with average weight of 24.88g and average length of 14.52cm, and 2,991 juveniles of O. niloticus with average weight of 24.90g and average length of 10.93cm were stocked at 30 fish/m 2 in clarias:tilapia ratios of 0:1, 1:0, 1:2, 1:4, and 1:6. The fish were fed at 3% body weight per day (BWD) over a period of 84 days. The monoculture of the two species (Treatments 1 and 2) yielded the lowest growth indices (WG, %WG and SGR), while the performance of clarias at each of the three polyculture systems were higher than those of tilapia. For clarias Treatment 5 (1:6) had the maximum length (17.92±0.37cm) while the monoculture recorded the minimum of 16.60±0.29. The monoculture of tilapia gave the lowest length gain (4.83±0.41cm) while the highest (11.60±0.51cm) for tilapia was recorded in Treatment 4 (1:4). From the regression parameters and the associated statistics (r and SE) for the validation of the models, it is evident that there was a strong positive relationship between length and weight. Even though the relationship was curvilinear there were still higher percentages of regression coefficient in all the treatments and between the species. The SE was also low in all the treatments which further validated the log transformed models. Therefore, the models are valid for estimating weight of the fishes from the length measurements without necessarily measuring the weight. Stocking ratio of 1:6 should be encouraged for better growth performance.