GENETIC VARIATIONS STUDIES OF WILD AND CULTURE CICHLID POPULATIONS Sarotherodon melanotheron IN LAGOS STATE, NIGERIA

Sarotherodon melanotheron (Ruppell, 1852) is a typical estuarine species which can be found in abundance in most of the lagoons and estuaries of West Africa which has been a major support to lagoon fishery. It can live and reproduce in a wide range of salinities. They have adapted to diverse habitats: permanent and temporary rivers, large equatorial lakes, tropical and subtropical rivers, open and closed estuaries, lagoons, swampy lakes, deep lakes and coastal brackish lakes (Trewavas, 1983). In this habitat, other species more traditionally used in tilapia culture are either not locally available or do not tolerate the prevailing saline conditions. Sarotherodon melanotheron, species is not well known for aquaculture purposes. Therefore, this study is carried out to establish the genetic characterization for the delineation of this Cichlid specie as an important specie not only for aquaculture and hatchery operations, but also for capture fisheries management.

A total of forty (40) samples were collected; 10 samples each of farm-raised (Akinsateru and NIOMR farms, Lagos) and wild (Lagos and Badagry Lagoon, Lagos). Random amplified polymerase DNA (RAPD-PCR) analysis was carried out using Operon primers (OPC 04, 05, 10, OPR 02 and OPI 05). Of the 5 primers, only 4 primers showed both stable amplification and polymorphism except on some samples having low reproducibility.

Figures 1. Shows the similarity coefficients of some of the individuals (SW6, SW7, SW13 and SW12) samples from wild to be 100 %.  The similarity from wild and culture were up to 82% and 88% respectively. Such genetic similarity in populations of a species from both wild and cultured has previously been observed for some tilapia species (Kusemiju, 2010).

This study therefore provides information on getting pure strains brood-stock from this natural water body, maintaining pedigree information of the brood-stock to avoid mating of close relatives and also needed for genetic information for effective decision toward managing the fish populations, for genetic manipulation in aquaculture; policy making, management and conservation.