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RANGE CONTRACTION MAY NOT ALWAYS PREDICT CORE AREAS: AN EXAMPLE FROM MARINE FISH
Author(s) -
Shackell Nancy L.,
Frank K. T.,
Brickman D. W.
Publication year - 2005
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1890/04-0642
Subject(s) - fishing , range (aeronautics) , population density , ecology , density dependence , abundance (ecology) , population , geography , fishery , population dynamics of fisheries , environmental science , fish <actinopterygii> , physical geography , biology , demography , composite material , materials science , sociology
Our goal was to identify the core areas of six severely depleted marine fish species on the Scotian Shelf, Canada, using the theory of ideal free distribution (IFD). We tested for density‐dependent distribution on both regional and local scales. At the regional scale, a density‐dependent response was observed in the majority of populations. At the local scale, density was expected to remain stable in areas of high density and to change more rapidly in marginal areas, in response to changes in regional abundance. Lower local density responses were associated with areas of higher density, but deviations were evident, in part due to the magnitude of decline and in part due to fishing effects. Former areas of high density can be eroded if the population has severely declined. Fishing directed at an area of high density can cause local depletion when recolonization rates are low relative to the intensity of fishing. Thus, areas occupied during periods of low regional abundance do not of necessity reflect the historical array of core areas. We do not recommend the use of IFD theory to identify core areas of heavily exploited species. Instead, we recommend a precautionary approach that assumes the existence of low‐mixing populations that can be differentially affected by fishing. For species at risk, only data derived before significant population declines should be used to identify high‐density areas. Such areas would represent those with the potential to support higher densities as well as the historical array of subpopulations. Our study provides insight into the practical aspects of analyzing exploited species using ecological theory.