Browsing by Author "Oduro, W."
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Item Functional relationship between crop raiding by the savannah elephant and habitat variables of the Red Volta Valley in northeastern Ghana(Pachyderm, 2012-07) Adjewodah, P.; Oduro, W.; Asase, A.We investigated the degree to which crop raiding by elephants in the Red Volta Valley is a function of: the density and diversity of their natural browse, extent of degradation of their habitat, and proximity of crop enclaves to the nearest forest boundary. We assessed 50 m × 5 m quadrats for browse and for agents of degradation (m2 of quadrat area clear-felled, burned, and surface mined), and we adopted records of cropraiding rates in 2000–2002 for correlation with habitat variables. We estimated the distance of affected enclaves from the forest, river and village using GIS; the total size of crop fields in a locale provided an estimate of the extent of cultivation. Using correlation and regression analysis, we examined for each locale the association between rate of crop-raiding incidents and the density and diversity of browse, size of crop fields, and distance of affected enclaves from the forest, river and village. We used a stepwise regression model to establish a functional relationship between crop raiding and the enumerated habitat variables. Second-order jackknife and Michaelis-Menten asymptotic estimators showed that the density and diversity of browse was near optimum. About 99% of the vegetation area sampled was burned, and 0.35 ha of vegetation was clearfelled for firewood. No evidence of mining was recorded. There was a significant inverse association between crop raiding and distance of affected enclaves from the forest, while the association between crop raiding and density and diversity of browse and the extent of degradation were not significant. A stepwise regression model gave a functional relationship between the observed rate of crop-raiding incidents and proximity of crop enclaves to the forest as Y = 25.105 + 3.2 – 9.73X (Y = rate of crop-raiding incidents and X the distance from enclave to the forest boundary). Contrary to speculation, crop raiding in the study area is not influenced by the status of browse, extent of degradation or size of cultivated fields. Thus, mitigation measures should include relocating farms away from forest reserves, while measures aimed at reducing the density of farms or replanting of the forest should be de-emphasized as they will not necessarily reduce crop raiding. © 2012, International Union for Conservation of Nature and Natural Resources. All rights reserved.Item Nature and patterns of lagoon fisheries resource utilisation and its implications to waterbird management in coastal Ghana(2008) Gbogbo, F.; Oduro, W.; Oppong, S.Seasonal patterns in human fisheries resource utilisation and the capture characteristics of fish, swimming crabs and land crabs harvested from four coastal lagoons in Ghana between September 2005 and August 2007 are described. These are discussed in relation to sustainable management of the lagoons’ fisheries for both human and waterbird use. With the exception of small pelagic foraging fish-eating birds, human fishing practices in the lagoons were in direct competition with crab- and fish-eating birds, because of the overlap of same-sized fish and crabs, and also in indirect competition because many of the exploited fish and crabs were immature. Fishing practices were also in direct competition with food foraging by invertebrate-eating birds. Intense exploitation of swimming crabs was linked to the use of drag nets, in comparison to the exclusive use of cast nets in some lagoons. In order to reduce the incidence of waterbird-human interactions and conflict during the energy-demanding phase of the birds’ non-breeding season, it is recommended that the practice of closed seasons be extended to include crab fisheries and be strictly enforced at all Ramsar sites on the Ghanaian coast.Item Response of waterbird species to fluctuating water levels in tropical coastal wetlands(2009) Gbogbo, F.; Oduro, W.; Oppong, S.K.Recent upsurges in the incidence of dam construction over rivers for farming and hydroelectric power in the West African sub-region is a known promoter of fluctuating water levels on tropical coastal wetlands. Waterbirds, being one of the dominant fauna on wetlands, are key species that can be affected by fluctuating water levels. Waterbird census and water level monitoring at four coastal wetlands in Ghana revealed that different guilds (species assemblages) of waterbirds responded differently to fluctuating water levels. The populations density of birds in guilds 1 (ducks and cormorants), 3 (tactile surface foraging waders), 4 (pelagic foraging waders) and 5 (stalking herons and egrets) significantly (P < 0.05) increased linearly with decreasing water levels. The population density of birds in guilds 2 (visual surface foraging waders) and 7 (fishing terns) responded significantly (P < 0.05) in a second order polynomial function with optimum numbers occurring when water levels were neither too high nor too low. As far as farming and energy requirement are met from these dams, it is important that the ecological needs of waterbirds on wetlands are incorporated into the management of these dams so as to maintain appropriate water levels beneficial to waterbird populations.