Survival and physical condition of sole and plaice caught with a 12 m pulse trawl and a conventional beam trawl

Beam trawling has effects on benthic organisms living on and in the sea bed. In order to reduce these effects and also minimize unwanted by-catches alternative ways of stimulating flat fish from the bottom are investigated. An associated question is whether the chances of survival of discard fish can be enhanced. Survival experiments on juvenile sole and plaice caught with a 12m prototype pulse beam trawl and a conventional tickler chain beam trawl were carried out in November-December 2004 and January 2005 onboard FRV “Tridens”. There is an indication that the pulse trawl causes a lower percentage of sole and plaice with severe skin damages.

A higher survival rate for plaice was found for the pulse trawl after 192 hours of observation, with higher values for damage category A than B+C. For sole an effect on the survival rate could only be demonstrated for damage category and not gear used. Nevertheless, the overall estimated percentages related to damage categories in a catch were relatively low.

The level of blood parameters (glucose, free fatty acids, cortisol, and lactate) and the changes over time in blood samples taken from both species showed no significant differences between both stimulation techniques.