Improving the sampling efficiency of benthic species and communities using complementary gears: beam trawl and bottom trawl

Abstract

[eng] Benthic species and habitats are receiving increasing attention in the framework of European regulations such as the MarineStrategy Framework Directive (MSFD) and the implementation of the Ecosystem Approach to Fisheries Management by the currentEuropean Union Common Fishery Policy. As a consequence, scientific surveys initially designed to assess demersal resources,like MEDITS, have broadened over the years from demersal species and their communities to benthic ones. At the same time, inthe framework of the MSFD, new specific surveys have also started to properly identify and characterize benthic communities.This work aims to compare the efficiency of Jennings beam trawl (BT) and the experimental bottom trawl GOC-73, to sampleepibenthic and nectobenthic species and communities. Thus, data from MSFD surveys were compared to data from MEDITS surveysin the Levantine-Balearic demarcation (western Mediterranean Sea). The Jennings BT provides better estimations of densityand species richness for small species closely associated with the seabed and the GOC-73 of the occurrence of some macroepibenthicspecies presenting low abundance. The GOC-73 allows for higher spatial coverage, but the Jennings BT gives more preciseinformation on the location of benthic species and the patchy distribution of benthic habitats. Although sampling was performed inthe same habitats, an important fraction of the species was collected exclusively using one or the other sampling gear. Both samplingmethods provide complementary information that improves biodiversity estimations and the description of benthic habitats,allowing a better future assessment of the anthropogenic impact, hence improving the objectives of the MSFD.