Survival of undersized plaice (Pleuronectes platessa), sole (Solea solea), and dab (Limanda limanda) in North Sea pulse-trawl fisheries

The European Commission landing obligation, including species-specific “high survival” exemptions, has established a need for accurate discard survival estimates. This study presents the first discard survival estimates on-board Dutch commercial pulse trawlers. During seven, six, and one fishing trip(s), respectively, undersized plaice (Pleuronectes platessa), sole (Solea solea), and dab (Limanda limanda) were collected, assessed for vitality and subsequently monitored up to 21 days. Uncorrected for any potential impacts from predation, tagging, research-related handling, or holding conditions overall survival for plaice (n¼349), sole (n¼226), and dab (n¼187) was assessed as 15% [95% CI: 11–19%], 29% [95% CI: 24–35%], and 16% [95% CI: 10–26%] respectively. Survival was mainly effected by water temperature and factors linked to the fishing vessel. Fish length was not found to affect survival. Catch processing time and haul duration affected plaice survival but not sole. Vitality index, which averages reflex impairment and external damage scores, correlated with survival and may be developed as a proxy for discard survival. Compared to tickler-chain beam trawlers, pulse trawlers showed relatively higher discard survival under fishing conditions pertinentto these studies