The cichlids of Eniong and Cross Rivers, Niger Delta, Nigeria

Abstract

Taxonomy and biodiversity is an important aspect of fish studies as it gives fish scientists information about the types of fish present, their name and classification based on discrete sets in a given locality. This study is on the taxonomy and bio-diversity of Cichlids collected from the Eniong River and the Lower Cross River in the Niger Delta, Nigeria between January and June 2020. A total of 358 cich-lids were collected from three sampling stations (the Eniong River, the confluence and the lower Cross River). Sampling was conducted with active and passive sampling techniques with the help of local fishermen using various fishing gears including beach net (10 – 15 m length, 2 –3.5 m height, mesh size of 0.5 – 5cm), fixed gill net (40 – 60 m long, mesh size 15 – 57 mm), cast net (2 – 5 m diameter, mesh size 15 – 20 mm) and local traps (made from raffia palm). The sampling du-ration with the fishing gear and methods were approximately the same. Gill nets and traps were set between 1600 h and 1800 h and fishes caught were removed from the gear between 0600 h and 0900 h the next day. Fish were identified using morphological and meristic traits. The species found and percentage abundance were; Coptodon zilli (5.9%), Coptodon dageti (31.2 %), Coptodon guineensis (16. 4%), Hemichromis elongatus (6.4 %), Hemichromis fasciatus (2.2%), Ore-ochromis niloticus (5.3%), Oreochromis aureus (0.8%), Sarotherodon melanotheron (3.6%), Sarotherodon galileus (0.8%), Sarotherodon macrocephala (1.95%), Chromidotilapia guntheri (10.3%), Pelmatolapia mariae (12.3%), Tylochromis sudanensis (1.7%) and the unidentified species(0.8%). There was higher abundance of cichlids in Eniong River (36%) than in the confluence (34%) and lower Cross River (30%). Simpson’s diversity index was 0.97 - 0.98 in the three stations. Shannon-Wiener’s index of diversity was 2.18 in Station 1, 1.76 and 1.68 in stations 2 and 3 respectively. Margalef index of diversity was 2.05 in station 1 and 1.66 and 1.71 in stations 2 and 3 respectively. Some species ap-peared to be specific in their habitat; O.niloticus, O.aureus, S. macrocephala were found in freshwater. S. galileus in the estuarine habitat while all other spe-cies were found in all the stations. A dichotomous key which will serve as a guide for fish scientist in the field was prepared using morphomeristic characters.