I.T. Omoniyi’s research while affiliated with Federal University of Agriculture and other places

The influence of environmental variables on the seasonal and spatial distribution of plankton was studied for 24 months between February 2015 and January 2017 in the marine coastal water of Ogun State, Nigeria. The coastline was stratified into three sampling stations, and surface water samples were collected monthly per station for physico-chemical and plankton analyses. Mean values of physico-chemical parameters were: temperature (28.60±0.27°C), salinity (29.25±0.45‰), pH (7.38±0.07), electrical conductivity (42.13±0.33μS/l), total dissolved solids (29.59±0.30mg/l), dissolved oxygen (6.48±0.07mg/l), phosphate (1.36×10-2±0.39mg/l) and nitrate (2.25×10-2±0.65mg/l). The dominant phytoplankton and zooplankton groups were Diatomaceae (42.06%) and Calanoids (25.42%), respectively. Spatial diversity analysis of plankton in the study area showed that the highest (19, 35) species richness and abundance (5703, 12,452) for phytoplankton and zooplankton, respectively occurred in Site 3. Seasonal species richness of phytoplankton and zooplankton was higher in the wet (27, 40) than the dry (23, 38) season. Canonical correspondence analysis explained 77.8% of the influence of environmental variables on plankton distribution. Water temperature, dissolved oxygen, salinity, phosphate, pH, TDS and nitrate were the most marked factors that affected the distribution and abundance of plankton.

The study examined the feasibility of a small scale integrated fish cum poultry farming project utilizing concrete tank of 4 x 4.8x3.5m. 900 post fingerlings of Clarias gariepinus (52 2.7g) were stocked in 3 concrete tanks at the rate of 1fish per 5m2 and fed diets containing 38% (Diet 1). 33% (Diet 2) and 31% (Diet 3) crude protein levels. Three battery cages containing 15 laying birds were installed on each tank. The birds were fed with layer mash (CP 18%) while the fish were fed with 300kg of fresh maggots and pelleted feed. At the end of 213days, growth response and nutrient utilization of fish were based on Average daily weight gain, (DWG 4.48) relative growth rate (RGR 1834.27) and specific growth rate (SGR 1.39). Final weight ranged from 949.2g to 963.2g. Daily weight ranged from 4.46g to 4.52g. Feed cost for fish was drastically reduced while revenue from poultry was significantly increased. The profitability analysis of the operation showed that table size Charias production generated return to investment of 31.19%, a rate of return on fixed cost 163.79% and a rate of return on variable cost of (161.07). The financial analysis reveals a viable investment.

Fish is a major source of protein in human diets. Fish demand has been on the increase due to increase in human population which has resulted to wide gap between fish demand and supply. This study was carried out to elucidate the major fish species that are economically important in the study area. Assessment of fish catch composition was done in the marine artisanal fish sector of Southwest Nigeria Gulf of Guinea. The study area was divided into three strata with one sampling station selected from each stratum. Four canoes were sampled per site per month. Fish catches were sorted into taxonomic categories, counted, measured and weighed. Sixty-nine fish species from forty-two families were identified constituting fifty-nine finfish and ten shellfish species. Clupeid family had the highest contribution both by weight (40.5%) and abundance (53.7%). Sardinella maderensis was the most abundant species by number (30.6%) and weight (27.9%). Parapenaeopsis atlanticus (51%) was the most abundant shellfish while P. validus (87%) was the highest by weight. Fish production was highest in Station 1 both by weight (37%) and abundance (41%). The status of finfish species showed that five species were very common; four were common, fourteen uncommon and thirty-six rare. Among the shellfish species, three species were very common, none was common, three were uncommon and three species rare. Effective management of these fish resources is necessary to ensure fish food security.

Population dynamics and length frequency distribution of Sarotherodon galilaeus was investigated from commercial fishermen operating within Iken brushpark in the Ogun coastal estuary of Nigeria. The study was necessitated to provide information on S. galilaeus that has been listed in the IUNC as a threatened species. A total of 1,938 specimens with total length range of 11.0 – 11.9 to 41.0- 41.9 cm and corresponding weights of 27 g to 1,345 g were sampled. Mean TL ranged from 26.96±0.58 cm in February to 31.08±0.41 cm in June with corresponding mean weight of 517.20±26.45 g and 766.12±26.04 g. In terms of abundance, the month of April ranked as the highest (492) and the least abundance was observed in February (252). The contribution of size class 31.0-31.9cm dominates the stock. Bhattacharya’s Modal Class Progression Analyses depicts four distinct peaks representing age groups 1+ to 4+. The highest value of the exponent "b" of length-weight relationship and condition factor "K" was recorded in male fish. K value showed significant difference (p<0.05) within sex. The estimated growth parameters values using Von Bertalanffy Growth Equation from age lengths key data were: Asymptotic length (L∞) = 43.58 cm, Growth rate (K) = 0.81 yr-1, Total mortality (Z) = 2.64 yr-1, Natural mortality (M) = 1.42 yr-1, Fishing mortality (F) = 1.22 yr-1, Exploitation rate (E) = 0.46, longevity (Tmax) = 3.70 years, Length-at- optimum yield (Lopt) = 25.02 cm and Length-at- first maturity (L50) = 11.43 cm. Overview of the growth parameters analysis suggest that S. galilaeus is still under exploit and it longevity is also above the recommended limit of cichlids.

Phytoplankton composition, temporal distribution and diversity with physico-chemical water parameters were studied based on monthly sampling from three locations in the lake. The lake was delineated into three sampling areas. Each location sited in each sampling area. The study was carried out for the period of twelve months. Of the four groups identified in this study (Chlorophyta (52%), Bacillariophyta (26%), Cyanophyta (20%) and Xantophyta (2%) consisting of 54 species. Xanthophyta was less diverse with one representative while Chlorophyta had the highest number of genera. Highest taxa (37) was recorded in June. Simpson diversity and evenness indices were generally high during the study period with highest values of 0.96 (June) and 0.95 (December) and least in August (0.85) and (0.70) respectively. High correlation coefficients 0.91 and 0.75 recorded in the relationship among TDS/EC and air/water temperature respectively. Canonical correspondence showed strong relationship between EC and TDS which were favourably dispose to abundance of Aphanocapsa, Nostoc and Scenedesmus with negative response of Melosira, Polycystis, Amphora, and Microspora. The monitoring of the lake system is essential for its sustainable management.

Phytoplankton composition, temporal distribution and diversity with physico-chemical water parameters were studied based on monthly sampling from three locations in the lake. The lake was delineated into three sampling areas. Each location sited in each sampling area. The study was carried out for the period of twelve months. Of the four groups identified in this study (Chlorophyta (52%), Bacillariophyta (26%), Cyanophyta (20%) and Xantophyta (2%) consisting of 54 species. Xanthophyta was less diverse with one representative while Chlorophyta had the highest number of genera. Highest taxa (37) was recorded in June. Simpson diversity and evenness indices were generally high during the study period with highest values of 0.96 (June) and 0.95 (December) and least in August (0.85) and (0.70) respectively. High correlation coefficients 0.91 and 0.75 recorded in the relationship among TDS/EC and air/water temperature respectively. Canonical correspondence showed strong relationship between EC and TDS which were favourably dispose to abundance of Aphanocapsa, Nostoc and Scenedesmus with negative response of Melosira, Polycystis, Amphora, and Microspora. The monitoring of the lake system is essential for its sustainable management.

A survey of parasites of Tilapia species (Family; Cichlidae) was carried out at the Federal University of Agriculture, Abeokuta Reservoir. A total of 150 specimens belonging to four genera and species were examined for parasites. Of the total number examined 16.0% were infected with various types of parasites. Parasites encountered during the study included flagellate protozoan, Ichtyobodonecatrix (96.0%), species of annelid, Piscicola sp.(1.6%), species of nematode, Cucullanus sp.(1.6%), and species of cestode, Caryophyllaeidessp (0.8%). This result showed low prevalence of infection as well as low parasites diversity. The prevalence of infection was highest in Oreochromis niloticus (29.0%) and followed in descending order by Hemichromis fasciatus (16.7%), Sarotherodon galilaeus (14.3%)and Tilapia zillii (10.5%). The skin (60.7%), gills (36.9%), stomach (1.6%) and intestine (0.8%) were the locations infected and the skin supported the highest burden. The result also revealed that there were no significant differences between the size/age (X2=0.44; p>0.05)and sex (X2=1.38; p>0.05) and the degree of parasitic infection in this group of fishes. The economic and public health implications of these results in relation to fish-man interactions were discussed.

Most aquatic ecosystem services are in a state of decline and the harmful consequences of this decline could grow significantly worse if efficient management strategies and policies are not put in place. The growth and mortality parameters as well as exploitation rate of 2,121 Ethmalosa fimbriata were collected between February 2015 and January 2017 from Ogun marine coastal water for management and conservation studies. Growth parameters and performance index estimated based on the Von Bertalanffy model using routines in ELEFAN1 FiSAT II gave the asymptotic length (L∞) of 32.6cm, the growth coefficient (K) of 0.65yr-1 , the theoretical age at length zero 0.35-1 and the performance index ɸ of 2.8-1. E. fimbriata grew allometrically (negative) with an abundance of medium size specimens. This species indicated a bi-modal distribution of two cohorts within the population structure. The estimated average value of instantaneous rate of total mortality was 2.69-1 , natural mortality was 1.33-1 , giving fishing mortality of 1.36y-1 and the rate of exploitation, E at 0.51yr-1 indicating over-exploitation of the stock of this species. Therefore, some management actions are considered necessary for sustainable exploitation and conservation of this commercially important species of fish.