Better fishing tactics for eliminating by-catch
The 'Nephrops and cetacean species selection information and technology' (Necessity) project took a number of actions aimed at minimising the volume of by-catches in Nephrops and pelagic fisheries. The Necessity team designed the project with a view to maintaining the catch of targeted species, but with innovative modifications to existing gear and fishing tactics and the use of acoustic deterrents. Carried out in close collaboration with the fishing industry, proposed options were mindful of the end user, so as to ensure industry applicability as well as biological effects and socioeconomic consequences. Given that technology used in Nephrops fisheries brought in a variety of 'unwanted' species, it was determined that new developments should block the entrance or provide opportunities for escape. Once all proposals had been tested in a flume tank, researchers refined the most promising ones for field development in accordance with local conditions. Necessity reviewed an existing modelling tool for mechanical simulation of grids and panels and developed software to simulate the behaviour of animals both around devices and in the trawl. The potential for using passive rather than trawled gears was also tested in the Mediterranean. Project partners offered gear modifications capable of reducing the by-catch as well as cetacean mortality in pelagic trawl fisheries. Measures proposed were also based on study of the biology and behaviour of dolphins — the most common by-catch species. Developing solutions was hampered to an extent due to cetacean interactions with trawls being sporadic. Excluder devices, tested in the laboratory with select equipment being further developed in the field, included ropes or panels in the front and grids in the rear of the nets. However, the scope of the project did not allow for further research that would enable a better understanding of the escape mechanisms in order to optimise equipment. Also, efforts to develop acoustic deterrents, although with promising results, require more research. The project launched a website and set up a base for contacts and industry liaison groups, and undertook various communication activities to disseminate information and an interactive DVD. Necessity efforts constitute a step towards more marine-environment–friendly fishing practices.