Survival rates and physiological recovery responses in the lesser-spotted catshark (Scyliorhinus canicula) after bottom-trawling

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Vol. 233; pp. 1 - 9
• Main Authors: Barragán-Méndez, C., Ruiz-Jarabo, I., Fuentes, J., Mancera, J.M., Sobrino, I.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-07-2019
• Subjects: Bottom-trawling; Capture stress; Discard survival; Elasmobranchs; Fisheries physiological recovery; Scyliorhinus canicula; Bottom-trawling; Discard survival; Fisheries physiological recovery; Elasmobranchs; Scyliorhinus canicula; Capture stress
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2019.03.016

In 2019, Europe will adopt a no-discards policy in fisheries. This entails the landing of captured species unless strong evidence is provided supporting their survival and recovery after fishing. Thus, research on this topic is gaining momentum. Bottom-trawling, as a non-selective fishing method, is characterized by a high proportion of discards including vulnerable key species, such as demersal sharks. Their survival may also depend on capture depth. By paralleling onboard and laboratory experiments with the small-spotted catshark, Scyliorhinus canicula, we offer a robust experimental design to assess the survival of discarded sharks. Catsharks were captured by bottom-trawling at two depths (shallow ~89 m and deep ~479 m). Blood samples were collected following trawl capture and analyzed for stress biomarkers (lactate, osmolality, phosphate, urea). During recovery in onboard tanks, behavior was video-recorded and fish were re-sampled after 24 h. A second experiment was conducted in laboratory facilities to simulate air-exposure after trawling and to analyze the physiological recovery. Our results showed that 95.7% of the animals survived 24 h after trawling. We confirmed that trawling elicited acute stress responses in catshark but that they managed to recover. This was demonstrated by lactate concentrations that were 2.6 mM upon capture, but recovered to assumed baselines after 24 h (0.2 mM). Non-invasive video monitoring revealed behavioral differences with depth, whereby those captured at 89 m depth required longer to recover than those captured at 479 m depth. Implementation of standardized survival studies by fishery managers can benefit from holistic physiological approaches, such as the one proposed here.
•Physiological recovery and survival rates of a bottom-trawled shark were evaluated.•A new methodology for discard survival evaluation in bottom-trawling fisheries is described.•The lesser-spotted catshark (Scyliorhinus canicula) shows high survival and recovery rates.•This holistic approach may pave the way for the evaluation of commercial fish species.