Using electronic monitoring to record catches of sole (Solea solea) in a bottom trawl fishery

Samenvatting

Electronic monitoring (EM) is often presented as a solution to document all catches through video observations under the EU landing obligation. However, identifying small fish on video in large volumes of catch is challenging. In this study, logbook records were compared with video observations for catches to test efficacy of EM for different size classes of sole (Solea solea) on board bottom trawlers. Comparisons were based on: (i) systematic differences (paired t-test), (ii) linear correlation (Pearson’s r), and (iii) absolute agreement (ICC). Results suggest that EM of small individuals in mixed fisheries is not as effective as it is for large individuals. To improve efficiency for estimating quantities of
small fish, additional methods are required to enhance video review. One possible method for enhancing video review is using a protocol where crew arranged the individual fish in front of the cameras. Indeed, this study suggests that such a protocol substantially improves EM of the complete catch. However, the protocol requires an additional three minutes of processing time per haul for a single species. Given the large number of quota species under the landing obligation for this fishery, implementing the protocol thus comes with a cost for the fishing industry; the extra time needed to conduct a simple protocol probably would exceed 12 h per fishing trip.