Predicting changes to macrobenthic communities due to fishing disturbance in a shrimp fishing ground of the Mexican central Pacific

Abstract

[Abstract] We test predicted short-term structural changes in the macroinvertebrate assemblages of a shrimp fishing ground in the tropical Mexican Pacific subject to low effort with seasonal closures. During two years, five cruises were carried out sampling seven sites and four depths (20, 40, 60 and 80 m) along 100 km of coastline. A series of community structure descriptors were used to determine the ecological effects of fishing disturbances: ABC curves, W-statistic, normalized species size distribution as biomass spectra, spatial segregation index, Shannon- Wiener diversity index, species richness and biomass. Theoretical predictions of the effects of fishing on these indices were tested by comparisons of samples collected from successive open and close fishing seasons. ABC curves show fishing has produced a state of chronic disturbance in the macroinvertebrate community. Shortterm effects could be masked by natural seasonal and interannual environmental changes. Results of the analyses of short-term effects are not in agreement with the fishing disturbance theories; only in 31% of the cases the results obtained of comparisons between successive cruises to test the different hypotheses about the effects of fishing were in agreement with theory. The temporal trend of increase of the biomass and the decline of species richness, could evidence interannual effects. The complexity of the sources of variability in a exploited community forces to focus on temporal and spatial gradients to understand the community structural processes