Morphometric variations in Sarotherodon melanotheron (Pisces: Cichlidae) from Brackish and fresh water habitats in South-western Nigeria

A comparative racial study of Sarotherodon melanotheron (Ruppell) from brackish and fresh water habitats both in south-western Nigeria using morphometric and meristic characters to determine variations showed that they were phenotypically separable populations of the same species. The results revealed significant differences (P < 0.05) in body depth, caudal peduncle depth, number of gill rakers and scales on the lateral line which were suggested to have occurred as a result of difference in the temperature, salinity and substratum in the two water bodies. The results also implied that fresh water broodstock could be preferable to the brackish population for breeding programmes

Biological assessment of Oreochromis niloticus (Pisces: Cichlidae; Linne, 1958) in a tropical floodplain river

Biological assessment of Oreochromis niloticus was conducted monthly between January, 2004 and December, 2006 in 3 zones [(Zone I: upper Cross River (savanna wetlands) Zone II: middle Cross River(savanna/forest wetlands) and Zone III: lower Cross River (forest wetlands)] along 200 km length of the inland wetlands of Cross River, Nigeria. Major items in the diet of O. niloticus were algae and plant 38and 20.4% (Zone I), 21.7 and 18.0% (Zone II), 20.2 and 26.9% (Zone III), respectively. Diet breadth ranged from 0.820 - 0.913. Food richness and Gut Repletion Index were 12 and 100%, respectively. Sex ratio was 1: 1 (Zone1), 1:0.78 (Zone II) and 1: 0.89 (Zone III). Mean allometric coefficients (b) of the lengthweight relationship were 2.194 ± 0.215 (Zone I), 2.935 ± 0.333 (Zone II) and 3.03 ± 0.202 (Zone III).Fecundity varied from 70 eggs for fish (total length (TL) = 11.00cm and weight (W) = 37.9 g) to 502 eggs (TL = 25.8cm and W = 198.8g) in Zone I, 60 eggs (TL = 13.3cm and W = 19.8g) to 709 egg (TL = 26.5, W= 317.0) in Zone II and 110 eggs (TL = 13.7cm, W = 24.0g) to 811 eggs (TL = 22.8cm, W = 278.8g) in Zone III. Relationship exists between fecundity and body size. Mean condition index ranged from 0.770 ± 0.128 minimum for males at Zone I to 1.188 ± 0.157 maximum also for males at Zone III. Therefore, male O. niloticus were in better condition than females and the forest wetlands of Cross River (Zone III) offered more favourable living conditions for the species than the savanna wetlands (Zone I and II)

The Food Habits of Ctenopoma pethereci, Gunther (Pisces: Anabantidae) in River Oluwa, Ondo State, Nigeria

The natural foods of Ctenopoma pethereci from River Oluwa in Ondo State, South-west Nigeria, were urrence and points methods of analysis. The quantity of food in the full stomach constituted 0.83% of the body weight while food in the intestine formed 1.54%, thus, giving the quantity of food in the entire gut as 2.37% of the body weight. There was little or no qualitative difference in the food items found in the stomachs and intestines. The food items encountered in the gut covered a wide spectrum, and the species is shown to utilize a wider variety of plant materials than animals. The dominant plant source included diatoms, blue-green algae, green algae and higher plants, while the range of animals included rotifers, copepods and insects. Organic detritus also formed a substantial portion of its food which amounted to 98.94%. The study revealed that C. pethereci is an omnivore with herbivorous tendency in River Oluwa

Heavy metals contamination of Chrysichthys nigrodigitatus and Lates niloticus in Ikere Gorge, Oyo state, Nigeria

This study investigates the presence of heavy metal contamination of Chrysichthys nigrodigitatus and Lates niloticus. Adult C. nigrodigitatus and L. niloticus were obtained from fishermen in Ikere Gorge, Oyo state, Nigeria. Water samples were also collected during the wet and dry seasons of the year in the same locality. The presence of five metals were analyzed in both fish and water. Iron, copper, zinc, lead and manganese were investigated by atomic absorption spectrosocopy (AAS) in two separate experiments. In each case, four tissues; gills, bone, intestine and muscle were compared with the level of metals in the water. Lower concentrations of metals were recorded in water than in fish. Lower concentration of the metals found in fish and water was less than that recommended by the World Health Organisation (WHO) guideline for maximum concentration recorded in the tissue of the two samples. Iron was found to be dominant in the intestine of C. nigrodigitatus, while manganese was found to be highest in the bone of L. niloticus, copper recorded the least of all the metals. There is significant difference (P &lt; 0.05) in heavy metals concentration in the gill of C. niloticus and water, as well as the concentration in the intestine of L. niloticus and water. It was concluded that though the heavy metals of interest were present in measurable quantities, they were still within safe limits for consumption.Key words: Heavy metals, fish, gorge, contamination

Assessments of fish catch composition of marine artisanal fishery in the Gulf of Guinea, Southwest Nigeria

Fish is a major source of protein in human diets. Fish demand has been on the increase due to increase in human population which has resulted to wide gap between fish demand and supply. This study was carried out to elucidate the major fish species that are economically important in the study area. Assessment of fish catch composition was done in the marine artisanal fish sector of Southwest Nigeria Gulf of Guinea. The study area was divided into three strata with one sampling station selected from each stratum. Four canoes were sampled per site per month. Fish catches were sorted into taxonomic categories, counted, measured and weighed. Sixty-nine fish species from forty-two families were identified constituting fifty-nine finfish and ten shellfish species. Clupeid family had the highest contribution both by weight (40.5%) and abundance (53.7%). Sardinella maderensis was the most abundant species by number (30.6%) and weight (27.9%). Parapenaeopsis atlanticus (51%) was the most abundant shellfish while P. validus (87%) was the highest by weight. Fish production was highest in Station 1 both by weight (37%) and abundance (41%). The status of finfish species showed that five species were very common; four were common, fourteen uncommon and thirty-six rare. Among the shellfish species, three species were very common, none was common, three were uncommon and three species rare. Effective management of these fish resources is necessary to ensure fish food security.Key words: Artisanal fishery, Gulf of Guinea, species, abundance, Southwest, Nigeria