Status of the fin fish fauna of the upper Sombreiro River, Abua/Odual Local Govt. Area, Rivers State, Nigeria

Abstract

A twenty two weeks prelimnary study was carried out to assess the Status of the Upper Reaches of the Sombreiro River, one of the most important rivers in River state. A field survey was carried out in three sampling points in the Abua/Odual Local Govt. Area where fish samples were collected from the fishers and the Composition and Abundance assessed over the period using standard methods. Generally, the fish composition comprised of thirty seven (37) species in twenty (20) families from forty two thousand one hundred and twenty seven (42,127) individuals. However, through there was a weekly variation in composition following the seasons of the study from the dry season (weeks 1 – 14, Jan. to April) to the wet season (weeks 15 – 22, May to June). Some species were in the catch mainly in the rainy season (H. fasciatus) while others in the dry season (G. decadactylus, I. africana, L. dentatus) and some available through the period (O. mossambicus, T. zilli, and other Cichlid. The weekly composition showed a seasonal variation with two peaks in the wet season but a higher peak in composition in the late wet season. The relative abundance showed that S. maderensis had the highest percentage (57.17%) abundance followed by T. zilli with 5.83% , L. grandisquamis and L. falcipinnis with 3.25% and 3.57% respectively. The least abundant in descending order were, H. niloticus, and T. senegalensis (0.07% each), P. senegalensis (0.03%) and E. senegalensis (0.01%). Also, the weekly abundance of fish species revealed a seasonal variation in the abundance. Week 16 with 8.92% had the highest relative abundance but there was another peak at week 2. Week 7 (0.17%) had the least. These findings of greater composition and abundance in the dry season than the wet season were consistent with other works in the Niger Delta Area (Chindah (1994), Chindah and Osuamkpe (1997), Allison et al (1997), Ogamba (1998), Sikoki et al (1999), Nweke (2000), Ezekiel et al.(2002), Davis (2009), Onwuteaka (2015), Ibim and Owhonda(2017), Ibim and Bongilli (In press) . They reported salinity in the river and the presence/absence of food organisms were the main reasons. However, fishing pressure may be a major issue affecting the high number of rare fish species as they are well appreciated and attract good prices in the local markets. Inter/intra specific competition is another factor. This study therefore serves as baseline for a greater Research Survey and Bio-Monitoring for further assessment of the Fish and Fisheries, including the Ecosystem for documentation and proper management/conservation of the fish and fisheriess in the Upper Reaches of the Sombreiro River in Rivers state.