No abstract

The study of Physico-chemical parameters in earthen fish ponds in five Local government areas in Bayelsa State, Nigeria was conducted to determine the quality of water for pond fish culture from June to October, 2005. Water samples were collected from the ponds and analyzed using standard laboratory methods and procedures. The results showed variation in the observed parameters at the different sampling stations. Temperature ranged from 24.9+ 0.3 o C-25.3+0.30 o C, pH 6.24+ 0.02-6.68+0.10 and Ammonia-nitrogen (NH3-N), 0.34+0.20-0.55+0.20mg/l. Dissolved oxygen values were 2.8+0.20-6.6+0.18mg/l, Biological oxygen demand ranged 2.9+0.60-4.52+0.90mg/l and Total alkalinity as 43.1+18.0-93.70+46.53mg/l. Total dissolved solids varied from 27.9+4.7-145.40+91.01mg/l while Total hardness was 19.7+4.1-44.3+15.07mg/l and Turbidity as 20.6+3.2-45.1+15.07ppm. Electrical conductivity was from 117.3+91.01-378.4+130.2µmhos/cm. The values for NH3-N were higher than accepted values for fish culture while those of other parameters favoured good fish production. The observations in this study suggest that pond fish production in some freshwater areas of Bayelsa State in Nigeria could be practiced without adverse effects posed by the quality of water.

An experiment was conducted to compare the growth and economics of producing Clarias gariepinus in ponds (6.4x5.4x1.5m 3 ) and tanks (2.5x1.1x1.2m 3 ) for 56days. Fingerlings of Clarias gariepinus (mean weight, 1.80g and body length, 4.40cm) were stocked at 250 and 50 fish separately into each pond and tank in duplicates. Fish were fed a commercial feed containing 45% crude protein at 5% body weight. It was divided into two halves and fed at 1000 and 1600hours daily. At final harvest, the total yield of fish was significantly greater (P<0.05) in pond, 3.0kg than those in tank, 1.81kg. There was no significant difference (P>0.05) in mean weight gain (13.75+0.95g, 13.44+0.95g), condition factor (0.92+0.03, 0.91+0.03) and feed conversion ratio (0.56+0.01, 0.51+0.01) between fingerlings stocked in pond and tank. Fish in pond had higher percentage weight gain and specific growth rate while survival rate ranged 74.11+0.54-88.80+0.54% in the culture media. Net profits obtained were N4300 (pond) and N2250 (tank). The benefit: cost ratio was higher for tank (1.38) than for pond (1.19). The pond environment appeared more productive while the tank was more economical with higher benefit in this study.

The effects of four practical diets (3 commercial and one locally prepared) on growth, feed utilization and survival of catfish hybrid (Heterobranchus longifilis x Clarias gariepinus ) fingerlings were compared in plastic aquaria in triplicates for 56days. Diets differed in crude protein (CP) and digestible energy as follows: Commercial Diet 1 (39.73% CP, 3911.8Kcal/kg), Diet 2 (34.50% CP, 3926.8Kcal/kg), Diet 3 (45.37%, 3883.6Kcal/kg) and local Diet 4 (40.34% CP, 3861.8Kcal/kg). Observations made indicated higher performance in weight and percent weight gain (2.299g, 411%), specific growth rate (0.78% day -1 ), condition factor (0.96), feed conversion ratio (2.67) and protein efficiency ratio (10.73) for fingerlings fed Diet 3 than other diets. Commercial Diet 2 appeared to perform least among the test diets. Fish survival was high and varied between 76.7% (Diet 4) and 96.7% (Diet 1). These results demonstrated that catfish hybrid fingerlings can be successfully reared in aquaria with good feed conversion, growth and high survival on commercially or locally prepared diets with 45.37% CP and adequate energy.

The evaluation of nutrient composition in adult Chrysichthys nigrodigitatus (CN), Clarias gariepinus (CG) and Heterobranchus bidorsalis (HB) was determined on wet basis. A total of 60 samples (weight: 500g-1kg fish) comprising 20 of each species were gutted, washed, ground and analyzed for moisture, protein, fat, ash and carbohydrate, using standard methods. Results showed the mean values for moisture, protein and fat as 72.53+ 0.23 (CG)-80.73+ 0.23% (HB), 18.20+ 0.13(HB)-21.37+ 0.13% (CN) and 2.13+ 0.10 (CN)-7.25 + 0.10% (CG). The carbohydrate and ash values ranged 1.33+ 0.19 (HB)-2.55+ 0.19% (CG) and 1.63+ 0.09 (HB)-3.30+ 0.09% (CN). The caloric values for protein was 13.27+ 0.14 (CN)-17.22+ 0.14 Kcal/100g (CG), fat showed 27.26+ 0.19 (CN)-57.31+ 0.19 Kcal/100g (CG) and carbohydrate 1.17+ 0.34 (HB)-1.35+ 0.34 Kcal/100g (CN). The nutrients showed significant differences at p< 0.001 between the fishes examined. These catfishes were observed to contain adequate quality animal protein, fat and ash that would provide appreciable amounts of essential nutrients such as amino acids, fatty acids, minerals and energy to support human health.