Spatial patterns in impacts of fishing on temperate rocky reefs: Are fish abundance and mean size related to proximity to fisher access points?

Abstract:

Effects of fishing on marine communities are becoming increasingly evident, yet little is known of the spatial extent of impacts, particularly for multiple impacts distributed over broad scales. We tested the common perception that commercial and recreational fishing on inshore temperate reefs generate spatial impacts that diminish with distance from fisher access points. We collected data on harvested and non-harvested reef species using underwater visual censuses at 133 shallow rocky reef sites around Tasmania and tested for relationships between assemblage and species level indices of fishing impacts and distance to the nearest boat launching ramp. Slopes of size spectra of fish communities tended to decrease with distance from the nearest boat ramp, with this relationship apparently resulting from low numbers of large fish (> 30 cm TL) and a greater number of smaller fish (< 15 cm TL) at sites closest to access points. At the species level, relationships were evident either in the abundance of legal individuals or the mean size of harvested species with distance to the nearest boat ramp, except for rock lobster. Patterns for rock lobster differed when areas in which commercial or recreational fisheries dominated were considered separately from the statewide analysis. A pattern of increasing numbers of legal lobsters with increasing distance from boat ramps was observed, but only in the areas in which the recreational fishery dominated. Observed relationships in all species were consistent with greater fishing impacts at sites closest to boat ramps, with the exception of exploited wrasses. Banded morwong, which are subject to a live export fishery, appeared to be most affected by proximity to boat ramps. Conversely, no relationships were found between the abundance or size of the most frequently occurring non-harvested species and distance to boat ramps. These results support the hypothesis that greater fishing impacts occur at more accessible sites over the entire Tasmanian coastline. The variability of results among individual species are likely, at least in part, to be related to differences in fisheries characteristics such as vessel size and range, as well as the suitability of our methods for detecting impacts. The potential of such a pattern in fishing impacts to be evident in other locations will thus likely depend on characteristics of the particular fishes and fisheries.

Authors:

Stuart-Smith R. D., Barrett N. S., Crawford C. M., Frusher S. D., Stevenson D. G., Edgar G. J.

Year:

2008

Journal:

Journal of Experimental Marine Biology and Ecology

Reference Type:

344

Volume:

365

Pages:

116-125

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