A study of the haematological and serological parameters (e throcyte and leucocyte numbers, catfish groups from the fish farm of the African Regional Aquaculture Centre, Aluu, Port Harcourt, Nigeria. Erythrocyte and leucocyte counts showed intra-species variability, while fish size was found to be negatively correlated to haemoglobin concentration and haematocrit values; these are significant at P = 0.05 level. The serological results obtained were found to be similar to the pattern in humans.haematocrit, haemoglobin, blood group and genotype) is reporte 7 for four freshwater, pond-cultured

Abstract. Oocyte maturation, ovulation and spawning were successfully achieved in the African catfish, Heterobranchus longifilis Valenciennes, using frog pituitary extract. During artificial spawning, oocyte maturation and ovulation were induced at a dosage of 7mg per kg of individual fish weight. Latency period varied from 7 h at 29°C to 11 h at 25°C. Dead eggs became opaque between 8 and 10h after fertilization while embryogenesis was found to be temperature dependent. Mean hatching and larval deformity rates were 63·08%± 7·56 and 8·08%± 1·93 respectively. During induced natural spawning, the extract was applied at a dosage of 35 mg per kg of female fish weight. Spawning occurred between 10 and 11 h after hypophysation. Mean hatching and larval deformity rates were 41·38%± 8·48 and 10·00%± 2·00 respectively.

Variations in macrobenthic community structure in time and space along a pollution gradient were examined in a small Niger Delta creek in 2006-2007. Salinity fluctuated between fresh and mesohaline conditions with values ranging from 0.4 to 5.2, and conductivity ranged from 16.9 to 36.0 μS cm -1 . The upper creek was relatively free of gross pollution, with high dissolved oxygen and low nutrient and salinity levels. At its lower end, BOD 5 was relatively high and nutrient levels were high, indicating substantial organic input. The middle and upper creek were dominated by Naboandelus africanus, Appasus sp., Laccotrephes sp., Plea sp. (Hemiptera) and Georissus sp. (Coleoptera). Sensitive taxa such as Neoperla sp. (Plecoptera), Ecnomus sp. (Trichoptera) and Ephoron sp. (Ephemeroptera) were restricted to the upper creek. At the impaired site Neritina sp. (Mollusca), Sesarma sp. (Decapoda), Nereis sp. (Polychaeta) and Chironomus sp. (Diptera) dominated the assemblage. Canonical correspondence analysis indicated that dissolved oxygen, conductivity, total nitrogen, BOD and temperature structured the invertebrate assemblages. Overall, human activities and land-use practices around the creek resulted in varying degrees of habitat degradation and nutrient enrichment, reflected by the macroinvertebrate assemblages which can be used effectively to monitor the effect of such activities on Niger Delta creeks.

Clarias gariepinus and Heterobranchus Iongifilis were successfully hybridized to produce reciprocal F 1 progeny during a two-year study. C. gariepinus produced significantly heavier spawn than H. Iongifilisduring the same period. Fertilized eggs were incubated in aerated static-water in fibre-glass troughs, and hatching rates were not found to be significantly different (P < 0.05) between any two of the four catfish groups produced. Eight-day old fry of each group were reared in fertilized nursery ponds, and F 1 hybrids from H. Iongifilis maternal parent had the best growth and survival rates at the end of 18 days. The reciprocal cross showed intermediate growth rate between both parents. At harvest, differential growth was less pronounced among both hybrids than among the parents.

No abstract