Size spectra as indicators of fishing effects on coral reef fish assemblages

Graham, N.A.J., Dulvy, N.K., Jennings, S., and Polunin, N.V.C. (2005) Size spectra as indicators of fishing effects on coral reef fish assemblages. Coral Reefs, 24 (1). pp. 118-124.

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Abstract

The data requirements and resources needed to develop multispecies indicators of fishing impacts are often lacking and this is particularly true for coral reef fisheries. Size-spectra, relationships between abundance and body-size class, regardless of taxonomy, can be calculated from simple size abundance data. Both the slope and the mid-point height of the relationship can be compared at different fishing intensities. Here, we develop size-spectra for reef fish assemblages using body size- abundance data collected by underwater visual census in each of ten fishing grounds across a known gradient of fishing intensity in the Kadavu Island group, Fiji. Slopes of the size-spectra became steeper (F9,69=3.20, p<0.01) and the height declined (F9,69=15.78, p<0.001) with increasing fishing intensity. Regressions of numbers of individuals per size class across grounds were negative for all size classes, although the slope was almost zero for the smallest size class. Response to exploitation of each size class category was greatest for larger fish. Steepening of the slope with increasing fishing intensity largely resulted from reductions in the relative abundance of large fish and not from the ecological release of small fish following depletion of their predators. The slope and height of the size-spectrum appear to be good indicators of fishing effects on reef fish assemblages.

Item ID: 8865
Item Type: Article (Refereed Research - C1)
Keywords: ecosystem based fishery management; size spectra; coral reef fisheries; community structure; indirect effects; fisheries management
ISSN: 1432-0975
Date Deposited: 09 Mar 2010 22:43
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070402 Aquatic Ecosystem Studies and Stock Assessment @ 40%
07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070403 Fisheries Management @ 40%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 20%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8302 Fisheries - Wild Caught > 830204 Wild Caught Fin Fish (excl. Tuna) @ 100%
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