Anthropogenic Restructuring of Fiddler Crabs (Uca tangeri) Communities: A Solid Wastes Perspective

Abstract

AbstractThe constant increase in human populations and its associated activities has become a stress factor for ecological communities of the aquatic ecosystem/environment. The aquatic environment/ecosystem particularly, the intertidal zones, mangrove forests and wetland ecosystems serve as a refuge for a diversity of organisms including fiddler crabs (Uca tangeri), with habitation and protection often coming in the form of extensive mudflats/sandy beaches and dense vegetations. This study evaluated the effect of anthropogenic activities on fiddler crabs (Uca tangeri) population particularly, on the fragmentation/loss of their habitats due to impact from solid wastes. Habitat fragmentation and loss due to solid wastes along the intertidal zone could eventually lead to biodiversity loss. The decapods (fiddler crabs) are among the common burrowers found in the intertidal and wetland zones of the coastal environment in the Niger Delta, Africa and other parts of the world. They are in the family Ocypodidae and have a number of features (size and shape of eyestalk, antenna, carapace, pairs of walking legs with chelipeds, body colour and sexual dimorphism) that could easily distinguish them from other crabs. They play very important ecological roles and interactions that sustain their ecosystems, serving as prey and predators in the ecological food chain/web. Fiddler crabs actively participate in bioturbation and organic matter degradation which has significant effect on ecosystem health/processes and so contributes to ecological diversity. Therefore, the impact of solid wastes due to anthropogenic activities is a menace of concern to the ecology, activity and life of fiddler crabs. The domination of solid wastes on the intertidal zones of our estuaries and coastal system had caused serious habitat degradation and loss for fiddler crabs and other organisms. Review of studies within the Niger Delta (Iwofe, Eagle Island and Ibeto) in Africa indicated serious threats to the habitats and existence of fiddler crabs due to the menace of solid wastes, indicating they are endangered. Significant variation in fiddler crab holes between different sites suggested population density variation across the sites. This was attributable to the influence of solid wastes that had taken over and fragmented the habitats of these intertidal dwelling crabs. This also suggests the level of anthropogenic activities (municipal wastes from run-off and direct discharges into the aquatic environment) impacting fiddler crab habitats by blocking fiddler crab burrows and occupation of available shoreline space, dislodging the crabs from their habitats. Increasing population and change in consumption pattern are responsible for increased waste generation in surrounding towns and cities. Other factors related to anthropogenic activities such as dredging/land reclamation, urban development, waste from urban run-offs and direct disposal, exploitation of mangrove resources and commercial boat activities further fragmented and degenerated the ecology of this very important species. These anthropogenic impacts could lead to a decrease in available refuge for such intertidal dwellers (fiddler crabs) and further endanger them, which could expose the crabs to increased predation, mortality rate and an overall reduction in population and consequent biodiversity loss. Sequel to the important ecological roles of fiddler crabs, alteration of their population and behaviour may have an adverse effect on the habitat and ecosystem. This may lead to biodiversity loss and eventual loss of important ecosystems such as intertidal environments, salt marshes, mudflats and mangrove forests.KeywordsFiddler crabs-Uca tangeriAnthropogenic activitiesSolid wastesImpacts Conservation