Modeling the intensity of bottom trawling footprints.

AMOROSO, RICARDO O; JENNINGS, SIMON; PARMA, A. M.; COLLIE, JEREMY S; PITCHER, C. ROLAND

Conferencia; ICES Annual Science Conference 2019; 2019

ICES

Recent work has mapped the spatial distribution of bottom-trawl fishing, with high-resolution data from vessel monitoring systems (VMS), over wide areas of the continental shelf. These data have been used to derive a simple predictive relationship between the seabed area trawled at least once (trawling footprint) and the ratio of total swept area trawled annually to the total area of the shelf region (regional Swept Area Ratio, SAR). This relationship can be used to predict the size of the trawling footprint in areas where VMS data are unavailable. Bottom-trawling impacts depend, not only on the spatial footprint, but also on the distribution of trawling intensity within that footprint (i.e. how many times each subarea has been disturbed). Here we take the next step by fitting frequency distributions derived from high-resolution VMS data in order to predict the amounts of area trawled at each different frequency (0, 1, 2, etc?) in relation to the regional SAR. We test whether there is a general distribution (e.g. Tweedie distribution) that can be applied across fishing areas, accounting for covariates such as gear type. The anticipated results of this study include a more general understanding of the intensity distribution of fishing effort within the overall footprint and improved ability to predict the impact of trawling at regional scales.