The physiological response and recovery of a common elasmobranch bycatch species: the lesser spotted dogfish (Scyliorhinus canicula) subject to a controlled exposure event

The Common Fisheries Policy proposes the landing of all catch to encourage discard reduction, but may allow exemptions for species for which ‘scientific evidence demonstrates high survival rates’. This shows the importance of bycatch stress studies into capture method and treatment post-landing. The physiological responses of a non-commercially exploited elasmobranch, Scyliorhinus canicula, subject to a component of the fishing process, i.e. emersion, were examined by analysing a suite of biomarkers. Dogfish were exposed for 15 minutes and 40 minutes followed by recovery periods, and metabolites were then compared to baseline levels. Glucose, lactate, ammonia, adrenaline, white muscle lactate and white muscle pH were the chosen measured biomarkers. Groups exposed for 40 minutes compared to 15 minutes had higher levels of metabolites. Plasma glucose and lactate levels in groups exposed for 15 minutes and 40 minutes had not returned to baseline levels at 4- and 8-hour recovery points. All endpoints except plasma glucose and lactate returned to baseline levels (T0) at eight hours' recovery. Our results indicate that this species can recover after an emersion event, as signified in the revival of metabolites. Lower responses and quicker recovery of metabolites due to shorter exposure indicate that a protocol minimising deck-time exposure may increase survival. Primary and secondary indicators analysed in conjunction with each other result in a more complete profile. Baseline data recorded provide reference data for future stress studies or for comparing postlanding protocols involving threatened elasmobranchs in Irish waters.