An overview of gill net and trammel net size selectivity in the Mediterranean Sea

摘要

Mediterranean is one of the world's most heavily exploited seas, where more than 90 % of the assessed fish stocks are overfished. In this basin small scale fisheries (SSFs) play a major socioeconomic role in terms of fleet size, number of jobs and amount and value of landings. Passive nets (chiefly gillnets (GNs) and trammel nets (TNs)) are the most common fishing gears employed by SSFs. Since they are considered more selective and less harmful to stocks and habitats than other gears such as trawls, their selectivity and impacts are less explored. This study was performed to provide an accurate description of the selectivity of Mediterranean GNs and TNs in relation to legal provisions and the biological features of their most common target species. It was found that the minimum conservation reference size (MCRS) set for certain species is well under their length at first maturity (LFM) and does not contribute to sustainability. Moreover, a thorough overview of the technical features of Mediterranean passive nets highlighted that they catch mature individuals above the MCRS and are therefore size-selective. This characteristic goes a considerable way towards achieving several conservation priorities: to reduce fishing mortality, to minimize the capture of juveniles and discards, to spare sexually immature individuals, thus improving spawning stock biomass and increasing the yield per recruit while attenuating the impacts on benthic ecosystems.