Escape panels in trawls: does placement matter when every individual contacting the panel can escape?

Abstract

Escape panels are one of the bycatch reduction devices most used in trawl fisheries but their efficiency rely on fish actively contacting the panel to escape. To investigate if contact behaviour changes at different panel placements, we tested a 300 mm square mesh panel placed in the upper panel of the codend at 3, 4 and 7 m from the codline. Seven competing models of contact probability were fitted to the empirical data. Based on the results, we inferred that panel placement significantly affects escape efficiency due to a change in type of contact behaviour. Cod (Gadus morhua) showed a contact increasing with length when the panel was closest to the codline, while contact probability decreased with length at the other placements. Similarly, contact probability for plaice (Pleuronectes platessa) was found to increase with length at 3 and 4 m, whereas a length-independent contact best represented the data at 7 m. Finally, Nephrops (Nephrops norvegicus) had in general low contact probability. The results provide new knowledge regarding species and placement-dependent panel escape.