A multimetric-index approach using fisheries data to assess fish assemblage structure in relation to salinity gradient in a tropical West African estuary     

J Kantoussan  JM Ecoutin  R Laë  OT Thiaw  L Tito de Morais 《African Journal of Marine Science》2018,40(2):175-185

This study examines the effects of increasing salinity on fish assemblage structure in the Casamance Estuary, Senegal, using a series of indices. The study data were derived from commercial fishery surveys conducted between April and July 2005. Analysis of within-trophic-group diversity in the Casamance Estuary shows a significant drop in the diversity of apex predators in the upper, more saline reaches of the estuary. By contrast, primary consumers adapted well to salinity changes and exhibited higher taxonomic diversity in the upper reaches of the estuary than in the lower reaches. The findings also indicate decreases in average sizes of the landed species and the trophic levels among fish catches in the direction of the upper reaches. However, the catch per unit effort (CPUE) was globally higher in the upstream area of the estuary as compared with the downstream area. This increasing CPUE trend from the lower towards the upper reaches is attributed to (i) the high primary productivity in the upper Casamance Estuary; (ii) the increasing abundance of euryhaline fish species in an upstream direction; and (iii) ‘telescoping’ of the food chain through the presence of mostly herbivorous fishes in the upper reaches. Such a situation likely facilitated high fish production in the upstream area of the estuary, though multimetric indices indicated unfavourable living conditions for many fish taxa in this area.  相似文献   

The interaction of surface water waves with submerged breakwaters   总被引：1，自引：0，他引：1  

M. Christou  C. Swan  O.T. Gudmestad 《Coastal Engineering》2008,55(12):945-958

This paper concerns the behaviour of nonlinear regular waves interacting with rectangular submerged breakwaters. A new series of experimental results is presented and compared with numerical calculations based upon a Boundary Element Method (BEM) that utilises multiple fluxes to deal with the discontinuities encountered at the corners of the domain. Specifically, comparisons concern both the spatial water surface profiles at various times and the spatial evolution of the harmonics generated by the breakwaters, the latter being an important focus for the paper. The BEM is shown to accurately model both the water surface profile and the harmonic generation, provided the breakwater width is sufficient to ensure that flow separation is not a controlling influence. Furthermore, evidence is provided to confirm that reflection from rectangular submerged breakwaters is fundamentally a linear phenomenon.  相似文献   

Linearization methods and the influence of current on the nonlinear hydrodynamic drag force     

Ove T. Gudmestad  Senior Engineer  Jerome J. Connor  Professor of Civil Engineering 《Applied Ocean Research》1983,5(4):184-194

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