Questioning the effectiveness of technical measures implemented by the Basque bottom otter trawl fleet: Implications under the EU landing obligation

tThe selective properties of a bottom trawl fitted with a 70 mm diamond mesh codend and a 100 mmtop square mesh panel (SMP) for hake (Merluccius merluccius), pouting (Trisopterus luscus and Trisopterusminutus) and red mullet (Mullus surmuletus) were investigated over the period 2011–2013. The experi-ments were carried out over three separate cruises aboard two commercial Basque bottom otter trawlersin the Bay of Biscay area. “Fall-through” experiments were also undertaken to estimate the potential sizeselection of 100 mm square mesh for the same species. Results from the “Fall-through” experiments andthe at-sea selectivity cruises demonstrated that a 100 mm SMP has the potential to enable undersized andimmature individuals to escape through the meshes. However, the selectivity cruises demonstrated thatin practice, the SMP was largely ineffective at releasing undersized individuals as only a small fraction ofthe fish entering the trawl attempted to escape through the SMP during their drift towards the codend.The fraction attempting to escape was quantified by the “SMP contact probability” and was less than 4%for hake and red mullet and less than 15% for pouting. Furthermore, for each species, the release potentialfor the diamond mesh codend was found to be significantly lower than the length-at-maturity and thelegal minimum conservation reference size. On average, the proportions of the total catch of undersizedindividuals of each species retained by the gear, were 52%, 17% and 45% for hake, pouting and red mulletrespectively. Based on our findings, we conclude that the gear currently deployed by the Basque bottomotter trawl fleet operating in the Bay of Biscay is largely ineffective at releasing undersized hake, poutingand red mullet. The introduction of the obligation to land all catches, under the 2013 reform of the EUCommon Fisheries policy will create new challenges for the Basque bottom otter trawl fleet and therebyan incentive to improve selectivity to avoid unwanted catches of undersized individuals.

ALZORRIZ GAMIZ Nekane;  ARRREGI Luis;  HERRMANN Bent;  SISTIAGA Manu;  CASEY John;  POOS J. J.; 

2016-01-04

ELSEVIER SCIENCE BV

JRC95821

0165-7836,   

http://www.sciencedirect.com/science/article/pii/S0165783615301454,    https://publications.jrc.ec.europa.eu/repository/handle/JRC95821,   

10.1016/j.fishres.2015.11.023,