Diversity, distribution and abundance of fish species in Lake Asejire, Oyo State, Nigeria

Abstract

Aquatic systems in Nigeria have suffered stress induced by human activities which alter the natural composition of the water resources. This study investigated the diversity, distribution and abundance of fish species in Lake Asejire. The lake was partitioned based on accessibility into upper, middle and lower sections for the study. Fish species were sampled using monofilament gill nets with stretched mesh sizes ranging from 44.45-169.33mm. Water and fish species were sampled fortnightly for a period of twelve months. Water quality parameters: temperature (28.96±0.28oC), dissolved oxygen (5.6±0.13mg/l), pH (6.73±0.19) and conductivity (159.8±0.32μS/cm) measured were within suitable standard ranges for fish production in natural waters. A total of 16 species from 10 families were identified from the lake. Cichlids had the highest number of fish species (4) and relative abundance (66.82%) and Coptodon zillii was the most abundant fish species across the months and sampling stations (27.53%). The lower section of the lake had the highest relative abundance (52.90%) while the upper section of the lake had the least (16.14%) and the highest fish catch (13.35%) was in November. The species richness of the lake decreased from lower (S=16) to upper section (S=14), the middle section was highly diversified (H=0.73) with a combined value of H=0.67 for the lake. The fish species were evenly distributed across the lake with the highest evenness in the upper section (E=0.22). Simpson’s index was highest in the lower region (D=0.30) and there was a high probability of picking different fish species at random. Trophic grouping showed forage to carnivore (F/C) ratio of 2.06 indicating an unbalanced fish population based on food habit, which should be addressed. There is need for proper regulation such as enforcement of fishing seasons and fishing across the trophic levels to ensure sustainability of the fish resources in the lake.

Species diversity and catch per unit effort of fish in a perturbed tropical lake, Ibadan, Nigeria

“…and Ipinmoroti and Iyiola [39]. The preponderance of Cichlidae in the lake could be attributed to favorable factors including abundance of food resources, their prolific breeding capabilities, and strong adaptation to lacustrine conditions of the Lake [35].…”

Owalla Reservoir in South-western Nigeria: Assessment of Fish Distribution, Biological Diversity, and Water Quality Index

“…As the tolerance level to these water quality parameters differs with species, a slight increase or decrease beyond these levels can have adverse effects on aquatic life and their body functions [24], [26], [28]. Therefore, good quality water is essential for sustained growth and performance instead of meeting the ever-increasing fish demand based on population growth [13]. The mean water parameters measured across the sampling zones are presented in Dissolved oxygen is vital in respiratory activities as it affects the growth, survival, biology, and physiology of aquatic organisms [37].…”

“…Apart from mortality, it has been reported to cause several aquatic degradations, the gradual disappearance of fish species diversity, and altering the natural carrying capacity of the water body [52]. A major pollutant observed around the reservoir was agricultural activities which have the potential to divulge into the reservoir when there is run-off [13]. There isa dire need to check on this activity as it directly impacts the sustenance of the fish species and use of water as observed and reported by Abdel-Satar et al, [53] in the Nile River and Belal et al, [54] in Timsah Lake and the Suez Canal, Egypt where water pollution was attributed to run-off from agricultural fields.…”

“…The study of the inter-relationship between water quality and the fish environment is very important as the condition of the water determines the fish abundance and diversity [6]  [12]. Species have been reported to increase when the environmental variables are conducive and reduce when conditions are not favorable; as the condition for one species may not favor another [13]. Therefore, the quality of water must be checked so the aquatic biota can be healthy and sustained [14]  [15].…”

“…Diversity of Fishes from Zone B in Owalla ReservoirIn zone C, the diversity indices values are presented in Table12. The number of individuals and taxa Richness was observed to fluctuate across the months of study (September -August) with15,7,17, 81, 65,13,11,10,18,22,28, and 1, 3, 4, 6, 5, 2, 4, 5, 2, 5, 6 respectively. Fish species were more dominant in September as observed in zones A and B because the highest value was recorded in the month.…”