Flume tank trials to investigate the snagging of towed demersal fishing gears on boulders

Abstract

The snagging of towed demersal fishing gears on seabed features and obstructions can have economic, safety, ecological and environmental consequences. Nevertheless, very little is known about the snagging process, the extent to which it occurs and how best to mitigate it. Here we present the results of a systematic flume tank study to investigate which gear-types are more likely to snag on boulders, which part of a given gear snagging is more likely to occur, and what are the characteristic features of the boulders shapes and size that increase the likelihood of snagging. As a case study we focus on gears that are typical of Jammerbugt, Denmark and show that tickler chain beam trawls are more likely to snag, while the snagging likelihood of the otter trawl, Danish seine and chain mat beam trawl are similar. Our approach and the methodology we develop will help design safer and more sustainable gears that interact less with the seabeds habitats and features. They will provide insights as to which gears can be used on which fishing grounds, contribute to a reduction of abandoned, lost and discarded fishing gears (ALDFG), improve fisher safety, and help fisheries managers develop measures that will promote more environmentally friendly and sustainable fisheries.