FISH SPECIES DIVERSITY IN ASEJIRE LAKE IN OYO STATE, NIGERIA

Sekeenat Omowumi Sabitu
Aquaculture and Fisheries Management, Federal University of Agriculture Abeokuta, Ogun State
October, 2014
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Abstract

Diversity and physical and chemical parameters of fishes in Asijire Lake in Oyo State, Nigeria were studied for a period of seven months, from February to August, 2014. The study area was divided into four strata: one sampling site selected from each stratum. Fish catches were sorted into taxonomic categories, counted and weighed. Twenty – two fish species from fourteen families were identified constituting twenty – two fin fish species. Bagridae family had the highest contributionboth by weight (34.5%) and abundance (46.68%). Chrysichthys nigrodigitatus was the most abundant species by number (46.6%) and weight (34.3%). Fish production was highest both by weight and abundance. Monthly contribution by abundance was highest in May and least in July seasonally, fish production was higher both by weight and abundance in the wet season. High similarity index in species composition was observed, it showed that fish species have similar ecological characteristics and could co – exist except Synodontis batensoda. Simpson diversity index was highest (0.88) with low dominance value of (0.12). Ninety per cent of the fishermen used composite gillnets in their net fleet with the commonest mesh sizes of 50.8mm and 33.9mm. The value of physico -chemical parameters assessed included dissolved oxygen (7.7± 0.27mg/l), temperature (31.8 ± 0.55oC), PH (7.9 ±0.09), nitrate (6.90 ± 0.23mg/l), and phosphate (0.08 ±0.01mg/l). Others were conductivity (228 ± 18.09µm/cm), Transparency (1.5 ± 0.05m), total dissolved solids (99,000 ±71,500mg/l), Alkalinity (10.8 ± 1.75mg/l) and hardness (167 ± 3.27mg/l). Seasonally, no significant difference (p >0.05) in dissolved oxygen and pH was observed, while significant difference (p<0.05) was observed for nitrate, phosphate, total dissolved solids, transparency, alkalinity and hardness. Despite the on-going petro-chemical industrial development by the government in the study area, high fish species diversity and good water quality observed should be conserved for sustainable fisheries management.