Distribution and intensity of bottom trawl fisheries in the Patagonian Shelf Large Marine Ecosystem and its relationship with marine fronts

Abstract

Trawling is a major concern worldwide and there is considerable debate about its impact on marine ecosystems. The Patagonian Shelf Large Marine Ecosystem (PSLME) is an important fishing area in the Southwest Atlantic where bottom trawling is the dominant fishing method. We investigated the distribution of bottom trawl fishing within this region, defining the areas of highest trawling intensity (hotspots) and evaluating their relationship with marine fronts. We focused on the three main oceanographic fronts, the shelf-break front, the southern Patagonia front and the mid-shelf front. To estimate fishing effort and trawled areas, we used VMS data from 2006 to 2012. Despite being almost a fully trawlable shelf, we found that the spatial distribution of trawling activity is patchy and trawling hotspots were small, comprising annually <5% of the shelf extension or <7% of the total trawlable area. Contrary to what is believed worldwide, our findings suggest that over the PSLME the magnitude of habitat effects as a result of bottom trawling is relatively small. Regarding the three frontal systems studied, only the shelf-break front showed a positive relationship with trawl fishing activity. Although trawling hotspots did not overlap with marine fronts, the shelf-break front receives more trawling effort than expected. We hypothesize that this pattern is due to aggregation of species near or at the front taking advantage of the opportunities provided by this area.