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Macroinvertebrate fauna of Ogbei stream in Anambra state, Nigeria was studied from monthly samples taken from six stations or sites with a benthic scoop net and a serrated cylindrical sampler (SCS) for 12 months (May, 2002-Apri 2003). A to al of 11420 macroinvertebrates were col ected belonging to 4 classes, 13 orders, 28 families and 50 species. The fauna was dominated numerically by Insecta (98.29 %), Arachnida (0.81%) and Oligochaeta (0.66%). Diptera was the most abundant taxon (42.62%), fo owed by Odonata (36.89%), Coleop era (9.76 %) and Hemiptera (8.22 %). Station 3 had the highest percentage of abundance of the macrofauna (28.56 %) followed by station 2 (19.54 %). The highest faunal diversi y was recorded in station 6 The macroinvertebrate composition, distribution abundance and diversity were influenced by substrate composition, good water quality and availability of food. l, t l ll t t .

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Abstract. The African catfish, Clarias gariepinus Burchell and Clarias anguillaris L., were induced to ovulate in aquaria by the administration of human chorionic gonadotropin (hCG) and pituitary extracts of Clarias albopunctatus (Nichols & Lamonte) and frog, Rana elegans. For final maturation and ovulation in both species of Clarias, the total dosage of each hormone was inversely proportional to the initial oocyte diameters of the recipient females. The time of ovulation after the last injection (latent period) was significantly shorter (11–13h) in females with large oocyte diameters (>920μm) than in those whose mean oocyte diameters were less than 920 μm (13–16h) (P < 0·05). The mean dosage of each test hormone required to induce ovulation was lower in females with large oocyte diameters than in those with smaller oocyte diameters (<920μm). The mean percentage hatch did not depend significantly on the nature of the treatment (P > 0μ05) and was about 86%. Clarias albopunclatus and R. elegans, which are economically unimportant and abundant in Anambra River basin, Nigeria, could be used as effective sources of hypophyseal factors in Clarias breeding programmes.

A survey of macro invertebrate fauna of Anambra River was carried out for 22 months at Otuocha, Ogurugu and Nsugbe. The macro invertebrates were sampled using kick sampling techn ques and scoop nets. Sampled specimens were ident fied to generic level. During the study a total of 21 genera of macroinvertebrates belonging to 13 families were identified. The fauna was composed of Gyrinus sp. (29.2%), Macrobranchium sp. (19.6%), Ranatra sp. (13.2%) and Agabus sp. (3.5%). The margalef's index of fauna richness showed that Otuocha station had the highest species richness (12.70), followed by Nsugbe (7.01), and Ogurugu (6.80) stations. The least fauna diversity of 0 21 was registered at Nsugbe as against 3.15 at Otuocha and 0.86 at Ogurugu. The Mc Naughton community dominance index was more pronounced at Nsugbe (53.1) than at Otuocha (49.69) and Ogurugu (47.04). Jackson's fauna similarly index showed that the fauna at Otuocha and Ogurugu were more closely related (0.64) than the fauna at Nsugbe.

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