Spatial distribution of commercial dredge fishing effort: application to survey design and the spatial management of a patchily distributed benthic bivalve species
Julian J. Harrington A B , Jayson M. Semmens A and Malcolm Haddon AA Marine Research Laboratories, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Private Bag 49, Hobart, Tas. 7001, Australia.
B Corresponding author. Email: Julian.Harrington@utas.edu.au
Marine and Freshwater Research 58(8) 756-764 https://doi.org/10.1071/MF06101
Submitted: 13 June 2006 Accepted: 28 June 2007 Published: 27 August 2007
Abstract
The patchy spatial distribution of many benthic commercial bivalve species plays an important role in determining the fishing and management strategies applied within a fishery. This study used fisher catch-return data and high resolution Vessel Monitoring System (VMS) data to determine the distribution of fishing effort within a region opened to commercial dredge fishing during the 2003 Tasmanian commercial scallop (Pecten fumatus) fishery, Australia. Fisher catch return data suggested that most (88%) of the open region was fished, however, fine-scale VMS data showed that 50% of the fishing effort occurred within 0.85% of the total area available to fishing, and 95% of the effort occurred within ~12% of the open region. The distribution of VMS inferred that the fishing effort was found to be patchy at all measured spatial scales (5 × 5 km to 250 × 250 m grid cell sizes); however, the degree of patchiness decreased with lower spatial scale cell sizes. Significant differences in the dredged benthic communities recorded within regions exposed to different concentrations of fishing intensity (heavy, moderate and low) were observed, with low and moderately fished regions containing high abundances of screwshells and their associated hermit crabs. Water depth was found to explain some of these observed differences, suggesting that the results may be the consequence of fisher behaviour over pre-existing habitat types. The observed distribution of the fishing effort and scallop beds within the Tasmanian commercial scallop, Pecten fumatus, fishery suits a closed area spatial management strategy, with the areas opened to fishing potentially being of the same scale as scallop beds (km × km).
Additional keywords: benthic communities, fishing effort, scallop fisheries, spatial management, spatial scale.
Acknowledgements
Funding for this project came from the Australian Fisheries Management Authority (March 2003 survey) and Fisheries Research Development Corporation (November 2003 survey) (2003/017) to MH and JS. Further financial support was contributed by Tasmanian Department of Primary Industry, Water and Environment. We wish to thank the skippers and crew of the Dell Richey II for their support during the surveys. Thanks also to C. Gardner, P. Ziegler, H. Pederson and A. Hirst for their helpful comments on the manuscript.
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