Scale-dependent detection of the effects of harvesting a marine fish population

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Certain ecological processes dominate others at particular scales, and the response of populations to exogenous and endogenous forces are typically scale dependent. In spite of this central role played by scale, the temporal and spatial scales of human impacts on ecosystems and populations remain almost unknown. We applied a multiscale regression analysis to investigate the spatiotemporal scales which characterize the fisheries exploitation of yellowfin sole Limanda aspera in the Bering Sea. We found that harvesting affects the abundance of this species simultaneously at local and regional scales. At the local scale harvesting produced a negative effect on local fish densities, particularly in those areas and seasons of high fish aggregation, when both the vulnerability of the fish and the fishing effort increase. At the regional scale harvesting was characterized by a widespread negative effect on the whole fish population. Our findings demonstrate that (1) detection of the fisheries exploitation effects on natural populations is sensitive to the scale of investigation, (2) fisheries harvesting can simultaneously affect multiple ecological scales which are not linearly correlated with each other. We developed analytical techniques for the detection of scale-dependent processes, which can be readily applied to other systems. Our results provide insights on the risks of extrapolating the effects of harvesting on natural populations across scales, making the issues of scale and space central to the management and conservation of natural populations.

This work is funded by the NorthPacific Research Board as part of project 709. We are gratefulfor partial support from the US National Science Foundation(NSF-0934617) for L.C. and K.S.C.