The Ichthyofaunal Assemblage of the Lower and Upper Reaches of New Calabar River, Rivers State, Niger Delta, Nigeria

Abstract

A study was carried out to identify the food and ornamental fish assemblage of the Lower and Upper Reaches of the New Calabar River, Rivers State, Nigeria. Surveys were carried out at the Lower (brackish) and the Upper (fresh) water course of the River for a period of fifteen weeks.  A total composition of 92,385 fish specimens, representing 61 species, belonging to 54 genera, 41 families and 15 orders, were recorded from both sections of the river. An assessment of species abundance revealed the following sequence - Sardinella maderensis (19.48%), followed by Mugil cephalus (15.23%), Sierrathrissa spp (13.45%),Chrysichthys nigrogitatus (6.73%), Tilapia zilli (4.67%), Malapterurus electricus (3.25%) and the least were Callinectus marginatus (0.01%), Aplocheilichthys spilauchen (0.00%). Similarly, family abundance revealed that, the family Clupeidae dominated the river’s fish fauna having (32.93%) of the total catch, followed by Mugilidae (15.23%), Cichlidae (11.82%), Claroteidae (7.60%), Carangidae (4.32%), Alestidae (3.88%) while Belonidae (0.01) and Cyprinodontidae (0.00%) were the least abundant families. The abundance score of species indicated that, thirty four (34) species were dominant, four(4) species abundant, eleven(11) few and twelve(12) species rare. It was thus deduced that, the stretch of the river surveyed had a high total species composition, however the species/family abundance varied considerably.  This phenomenon may be due to differences in fish species tolerance for the varied physico-chemical parameters, as the river comprises of fresh and saline regimes. Further more, this variation in the physico-chemical parameters of the river system is also known to affect the food organism availability and their natural distribution, which in turn affects fish species composition, abundance and diversity. Also, environmental disasters, fishing pressure on certain species and hydrocarbon pollution along the river system are likely factors responsible for the variation in the composition, abundance and diversity of fish species. Also, for the species that were rare, their low numbers is no confirmation that these species are threatened/over-exploited. Rather there could be other reasons such as inter/intra-specific competition, natural low population, amongst others. It is therefore recommended that further studies be carried out to ascertain the true cause of the variations.

This study is essential, as it can be used as a baseline study for knowledge development,  and a guide for the management and development of the New Calabar River fish species for Aquaculture and Ornamental fisheries sector, and the Protection/Conservation of the fish species. The document can also be used as a guide for Biological monitoring of the river system in case of Hydrocarbon Exploration/Pollution and for the management and development of the New Calabar River Fisheries.

Keywords: Ichthyofaunal Assemblage, Lower New Calabar River, Upper New Calabar River, Niger Delta Area.