COMPOSITION, ABUNDANCE AND DIVERSITY OF THE FAMILY CICHLIDAE IN OYAN DAM LAKE (OGUN STATE, NIGERIA)

Headnote

KEYWORDS: Composition, abundance, condition factor, diversity, Oyan dam.

ABSTRACT

A study was conducted to determine the status of the family Cichlidae in Oyan dam, Nigeria, during the wet and dry seasons of 2011. The specimens were collected in a standardized way, using multi-mesh gill nets of different size ranges (30 mm - 80 mm). The richness of the species was determined by Simpson's index of diversity, and species dominance and evenness by the Shannon-Weiner index of diversity. A total of 547 individuals were caught from Ibaro (S1) and Imala (S2) sites of the dam. The species collected included Sarotherodon galilaeus (42.60%), Oreochromis niloticus (17.92%), Tilapia zillii (25.41%), Hemichromis fasciatus (10.61%), and Tilapia mariae (3.48%). There were juveniles, sub-adults and adults in the catches. The sizes were from 12.85 ± 0.29 cm SL, 109.22 ± 6.00 g BW in Tilapia zillii, to 6.09 ± 0.05 cm SL and 8.07 ± 0.15 g BW in Hemichromis fasciatus. The diversity indices of cichlids indicated low diversity at the two sites observed in the Oyan dam. These indices from the sites (S1, S2) were D = 0.284 and 0.294, respectively; Simpson's index of diversity and reciprocal indices were (0.716, 0.703) and (3.521, 3.367), respectively. H = 1.36, 1.37, while J = 0.845, 0.852 at the two sites. Sarotherodon galilaeus, Oreochromis niloticus, Tilapia zillii, and T. mariae exhibited a positive allometric growth pattern, while only Hemichromis fasciatus showed a negative allometric growth.

RÉSUMÉ: La composition, l'abondance, les facteurs de conditions et la diversité de la famille des Cichlidés dans le réservoir d'Oyan (Etat d'Ogun, Nigéria).

L'étude a visé la détermination du statut présent de la famille des Cichlidés dans le réservoir d'Oyan, Nigéria, durant les saisons sèches et humides en 2011. Des échantillons ont été collectés de manière standardisée à l'aide de filets multi mesh à plusieurs gammes de dimensions (30 mm - 80 mm). L'indice de diversité de Simpson a été utilisé pour calculer l'abondance et l'indice de diversité de Shannon-Wiener a été utilisé pour calculer la dominance et l'equitabilité. Au total, 547 individus ont été captures dans lac au niveau des stations d'Ibaro (S1) et d'Imala (S2). Les espèces collectées comprennent Sarotherodon galilaeus (42,60%), Oreochromis niloticus (17,92%), Tilapia zillii (25,41%), Hemichromis fasciatus (10,61%) et Tilapia mariae...