Lower Ogun River Research Articles

Length–weight relationship of Tilapia mariae in Lower Ogun River, Akomoje Water Reservoir, Nigeria

The length-weight relationships and the condition factor of the fish Tilapia mariae were examined in the laboratory. The fish species attained a mean standard length in the range of 13.12±0.61 cm in male, while it was 19.83±0.76 cm in female. The growth in length relative to weight was negative allometric. There was variation in condition factor (k) for both sexes. The females were in better condition than the males whose k-values were higher during the dry and wet seasons. The sex ratio of Tilapia mariae in the reservoir was 1:3.12 (M: F), with September showing the highest sex ratio of 1:3.17 (M:F) and October showing the least 1:2.05 (M:F).

Assessing marginal wetland loss to agricultural expansions in the Lower Ogun River Basin of Southwest, Nigeria

Wetlands are significant to the environment and economic survival of people most especially in the rural areas of the tropical world; their sustainability is however threatened by agricultural drainages and demographic pressure. The detrimental influence of agricultural expansion on wetland loss was examined using both primary and secondary data. The primary data was collected through questionnaires administration and interviewing of hundred members of Fadama Users Group (FUG) (i.e. 10%). The secondary data included satellite images of 1972, 1984, 2000 and 2015 analyzed using GIS technique and corresponding census data by simple descriptive percentage method. The results revealed that marginal wetlands lost about; 3180.60 ha between 1972 and 1984, 1936.08 ha between 1984 and 2000 and 805.32 ha between 2000 and 2015, to farmlands intensification throughout the periods of study. Wetlands ecosystem was also expected to lose more ground as the population growth is unabated and, more so, with the projected farmlands growth of about 4730.04 ha i.e. about 36.36% in 2030; there is, therefore tendency for serious depletion of marginal wetlands in the future.

Water Level and the Potentials for Wetland Formation and Sustainability in Lower Ogun River Floodplain, Nigeria

Identification, delineation and monitoring of wetlands which requires the understanding and application of their ecological characteristics are critical factors in wetland management and conservation. This study assessed the potentials of wetland formation and sustainability in the lower Ogun river basin by determining the levels of surface and ground water. The study area was divided into 1 km2 grids of 67 units using 0.052 % sampling intensity for the assessments in dry and wet seasons. Monthly water table levels were assessed in 50 cm soil pit while inundation levels were measured during the flooding event using staff gauge. Assessment was carried out for one year during which frequency and periodicity of water table and inundation events were recorded. Results revealed that low water table level ranged from 5 to 45cm of soil depth and occurred between August and September within 6 grids. Water table and surface water was recorded within a period of 2 – 10 weeks during the rainy season. The peak of water levels coincided with the peak of precipitation (> 200 mm) ranging from 30 to 280 cm between September and October while covering 28.75 km2. Conclusively, surface and groundwater levels were recorded during the rainy season having direct variation with the volume of precipitation for a duration that is long enough to support the formation of wetland hydrophytes and hydric soil.
 Keywords: Wetlands; Hydrology; Ground water; Surface water; Inundation; Precipitation

Environmental factors and pattern of riparian vegetation along the downstream sections of the Lower Ogun River, Nigeria

The River Continuum Concept (RCC) is an existing theory regarding the distribution of plant communities along riverbanks. This study is concerned with the pattern of riparian vegetation along the Lower Ogun River (LOR) in relation to the observed downstream variation of various environmental factors (bank height, width, gradient, distance, cross‐sectional area and particle size). The LOR transits between undisturbed and disturbed sections. Forty‐eight cross sections were established at bankfull stage along the river channel stretch of about 90 km. Environmental variables distribution were determined using standard field procedures. Gradient was estimated from a 1:50 000 topographical map. At each corridor along the study sites, a 0.1 ha sampling site was chosen, in which 10 transects of 100 m2 were demarcated. In all, 332 individuals stratified under 80 species were recorded across the transects. The study revealed that total species richness (TSR) downstream decreases exponentially. TSR is significantly correlated with channel width, suggesting that hydraulic variable contributes more to the variation in TSR. The downstream total environmental factors revealed that width is inversely significant with downstream distance, suggesting that the river channel is narrower downstream. This affects plant life form distribution downstream and confirms why there is appearance of anthropogenic induced species downstream as against those in the upper course.

Water quality in relation to plankton abundance and diversity in river Ogun, Abeokuta, Southwestern Nigeria

Aims: Plankton abundance and diversity are governed by certain aquatic environmental factors which collectively determine the health of the aquatic ecosystem. This study was aimed at investigating the water quality of lower Ogun River, Abeokuta, in relation to plankton abundance and diversity. Materials and Methods: The dataset consists of physicochemical and plankton data collected for 7 months within the period of December 2011 and June 2012 in four stations. Spatial correlations were determined between physicochemical parameters, plankton abundance, and diversity. Physicochemical parameters that exhibited strong correlation with plankton abundance and diversity were used in the calculation of a water quality index (WQI) for the protection of aquatic life. Results: Results showed highly significant correlations (P ≤ 0.05) between plankton abundance, diversity, and the physicochemical parameters monitored during the study period excluding alkalinity and phosphates. The Canadian Council of Ministers of the Environment WQI showed that the river water quality in all the sampled stations (A, 63; B, 63; C, 56; and D, 64) was marginal in classification. Conclusion: It was concluded that River Ogun is polluted beyond doubt. Hence, corrective measures should be put in place so as to prevent total ecological collapse.

Investigation of biological condition of fish species in lower Ogun River wetlands, Lagos, Nigeria

The study was carried out to investigate the biological condition of fish species in lower Ogun River wetlands. A total of 175 individual fish belonging to 10 species were collected from artisanal fishermen usingdifferent types of fishing gears. Two biological indices; condition factor “K” and growth exponent “b” obtained from length-weight relationship were used to determine the biological condition of the fishes. The conditionfactor (K) recorded during the study ranged between 0.55 in Liza grandisquamis and 5.61 in Oreochromis niloticus. The growth exponent (b) ranged from 1.48 in Penaus notialis to 5.67 in Gymnarchus niloticus. Theregression coefficient of determination was significant for some of the fish with highest value of R2=0.98 for Sardinella madarensis. The study showed that most of the fish species in the study area are in poor biologicalcondition and exhibit allometric growth.Keywords: Allometric growth, condition factor, growth exponent, length-weight relationship.

Assessment of Environmental Responses to Land use/Land cover Dynamics in the Lower Ogun River Basin, Southwestern Nigeria. Abstract

This study investigated the pattern of land use/land cover change in the Lower Ogun River Basin between 1984 and 2012. Two sets of topographical map, a LandSat-5 TM image of 1984, LandSat-7 ETM+ of 2000 and a Google Earth image of 2012 were used for the study. The topographical maps and satellite images were digitally processed using ILWIS 3.2 software and exported to ArcGIS 9.3 for further processing and analysis. The processed images were subsequently classified using the maximum likelihood classification algorithm, resulting in the identification of seven land use classes, which are, farmland, forested wetland, light forest, non-forested wetland, shrub, urban and water body. Furthermore, change detection analysis was carried out using the cross module of the ILWIS software. The result of the change detection analysis indicated that between 1984 and 2000, 80.08 % of the land cover in the area has been converted to other land uses while only 19.92 % remained unchanged. Also within the same period, light forest, non-forested wetland and forested wetland decreased at average rates of 8.26, 4.66 and 2.81 (%) per annum respectively, while water body also decreased at an annual rate of 0.17 %. On the other hand farmland, shrub and urban/built-up areas expanded at average rates of 7.23, 6.74 and 4.65 (%) respectively. The result further indicated that between 2000 and 2012 49.86 % of the land cover has been converted to other land uses, while 50.14% remained unchanged, and that farmland, shrub, urban/built-up and forested wetland, expanded at average rates of 6.01, 1.95, 0.89 (%) and 0.17 % per annum respectively, just as Light forest, non-forested wetland and water body decreased by 8.26, 2.70 (%) and 1.40 % annually. Five composite soil samples each to the depth of 0-20 cm were randomly collected and analyzed for their physicochemical properties using standard methods to determine the impact of land use/land cover change on soil quality in the selected forested and non-forested wetlands. The findings have shown the growing impacts of urban agriculture on the wetland ecosystem within the study area; resulting in soil degradation and biodiversity loss. The implication of these findings is that the area is made to be susceptible to devastating flooding which can culminate in the loss of lives and properties. The study therefore recommended the development of effective land management information system and policies that will ensure sustainable management of fragile ecosystem. Keywords : change detection, river basin, urban agriculture, land use/land cover, satellite images, soil degradation, Wetlands. Normal 0 false false false EN-GB X-NONE X-NONE

English

This study investigates the pattern of land use/land cover change in the Lower Ogun River Basin between 1984 and 2012. Two sets of topographical maps, a Landsat-5 TM image of 1984, Landsat-7 ETM+ of 2000 and a Google Earth image of 2012 were used for the study. The topographical maps and satellite images were digitally processed using ILWIS 3.2™ software and exported to ArcGIS 9.3™ for further processing and analysis. The processed images were subsequently classified using the maximum likelihood classification algorithm, resulting in the identification of seven land use classes. Furthermore, change detection analysis was carried out using Cross Module in ILWIS™. The result of the change detection analysis indicated that between 1984 and 2000, 80.08% of the land cover in the study area has been converted to other land uses while only 19.92% remained unchanged. Also, within the same period, light forests, non-forested wetlands and forested wetlands decreased at average annual rates of 8.26, 4.66 and 2.81%, respectively, while water bodies also decreased at an annual rate of 0.17%. On the other hand, farmland, shrubs and urban/built-up areas expanded at average annual rates of 7.23, 6.74 and 4.65%, respectively. The result further indicates that between 2000 and 2012, 49.86% of the land cover has been converted to other land uses, while 50.14% remained unchanged, and that farmlands, shrubs, urban/built-up areas and forested wetlands expanded at average annual rates of 6.01, 1.95, 0.89 and 0.17%, respectively, just as light forests, non-forested wetlands and water bodies decreased annually by 8.26, 2.70 and 1.40%, respectively. Five randomly collected soil samples were analyzed for their physicochemical properties. Findings show the growing impact of urban agriculture on wetland ecosystem within the study area, manifesting in soil degradation and biodiversity loss. The implication of these findings is that the area is susceptible to devastating flooding which can culminate in the loss of lives and properties. This study recommends the development of effective land management information system and policies that will ensure sustainable management of fragile ecosystem. Key words: Change detection, river basin, urban agriculture, land use/land cover, wetlands.

Physical and Chemical Parameters of Lower Ogun River Akomoje, Ogun State, Nigeria

The aims of carrying out this experiment were to determine the water quality and to investigate if the various human and ecological activities around the river have any effect on the physico-chemical parameters of the river’s resources with a view to effectively utilizing these resources. Water samples were collected from two stations on the surface water of Lower Ogun River Akomoje biweekly for a period of 5 months (Jan-May, 2011). Results showed that temperature ranged between 24.0-30.7oC, transparency (0.53-1.00 m), depth (1.0-3.88 m), alkalinity (4.5-14.5 mg/l), nitrates (0.235-5.445 mg/l), electrical conductivity (140-190 μS/cm), dissolved oxygen (4.12-5.32 mg/l), phosphates (0.02 mg/l-0.75 mg/l) and total dissolved solids (70-95). The parameters at the deep end (station A) accounted for the bulk of the highest values; there was however no significant differences between the stations at P<0.05 with the exception of transparency, depth, total dissolved solids and electrical conductivity. The phosphate value was relatively low which accounted for the low productivity and high transparency. The results obtained from the physico-chemical parameters agreed with the limits set by both national and international bodies for drinking and fish growth. It was however observed that during the period of data collection, catches was low and this could be attributed to low level of primary productivity due to the quality of physico-chemical parameters of the water. It was recommended that the agencies involved in the management of the river should put the right policies in place that will effectively enhance proper exploitation of the water resources. More research should also be carried out on the physico-chemical parameters since this work only studied the water for five months.

Comparative Study of Soils Derived from Sedimentary and Basement Rock Formations of the Lower Ogun River Floodplain, South Western Nigeria

The anisotropic nature of soils makes it imperative to study the associations of soils and regional landscapes for sustainable land use planning and management. This paper examines soil properties involving four catenas on two parent rock formations in two ecological zones. It simultaneously studied the vertical and lateral variations of soil properties in relation to parent materials, slope positions and pedogenetic-geomorphic processes along hillslopes extending over basement complex and sedimentary rock formations of the Lower Ogun River Floodplain. The different parent materials from different parent rocks, slope positions and pedogenetic-geomorphic processes accounted for the intra-profile and inter-profile variations of topsoil and subsoil properties in the landscape. The study demonstrated that in a given hillslope, topsoil and subsoil properties show more significant differences (p<0.05) between diverse rock formations, distinct parent materials and different slope positions than within them. This suggests that the soils are genetically linked due to the influence of relief (differences in elevations) along the hillslope and geomorphic factors (parent materials) which affirms catenary associations of soils along the hillslopes.

Population growth of three freshwater prawns (&lt;i&gt;Macrobrachium&lt;/i&gt; spp.) in Lower Ogun River, Southwest Nigeria

Growth parameters of the populations of three freshwater prawns: Macrobrachium vollenhovenii, M. macrobrachion and M. felicinum in the Lower Ogun River were determined. For each population, lengthfrequency data for twenty-four month period (January 2006-December 2007) were analysed to determine the growth parameters, using routines in FAO-ICLARM Stock Assessment Tools (FISAT II). Estimates from FISAT indicated steady growth of the three populations. M. vollenhovenii had mean maximum length (Lmax), asymptotic length (L∞), performance index (o’) and growth coefficient (K) of 187.00 mm ± 5.66, 215.10 mm ± 16.27, 3.98 ± 0.04 and 0.2 ± 0.04 respectively. Mean values for Lmax, L∞, o’ and K for M. macrobrachion were 86.00 mm ± 1.00, 100.26 mm ± 12.20, 0.59 ± 0.16 and 3.76 ± 0.01 respectively, while 76.45 ± 3.25, 69.00 mm ± 1.00, 1.33 ± 0.67 and 3.87 ± 0.19 were the respective mean values of the growth parameters for M. felicinum . The suitability of the Macrobrachium species for aquaculture based on the estimated growth parameters is discussed. Keywords: Lower Ogun River, Asymptotic length, Maximum length, Growth performance index, Growth coefficient

A study on the macroinvertebrate fauna of lower Ogun River at Ishasi, Ogun state, south-west Nigeria

The composition, distribution and abundance of macroinvertebrate fauna of Lower Ogun River were studied at Ishasi from January 2006 to December 2007. Bank-root macroinvertebrates were sampled using kick sampling and scooping gear while Ekman grab were used to sample the mid-channel from three stations with 200m intervals on monthly basis. Physico-chemical parameters were also measured and found to be within the ranges suitable for normal aquatic life. A total of 27,005 macroinvertebrate individuals from forty-five taxa were collected from the entire study area (pooled data of the three stations). Three Macrobrachium species dominated the macroinvertebrate fauna. Class Insecta had the highest number of representations with thirty-three taxa cutting across eight orders including the pollution sensitive/clean water ones (Odonata, Trichoptera, Plecoptera and Ephemenoptera). Margalef species richness and Shanon-Wiener diversity indices levels of 4.41 and 1.18 respectively were recorded from the study area. The three sampling stations had insignificantly different physico-chemical parameters, macroinvertebrate abundance and diversity levels (p>0.05), which indicate uniform ecological conditions within the study area. The findings indicate a relatively stress free environmental condition within the study area.Key words: Macroinvertebrates, Physico-chemical parameters, Species composition, Diversity, Abundance.