Discard Survival of Thornback Ray ( Raja clavata ), Undulate Ray ( Raja undulata ) and Small‐Eyed Ray ( Raja microocellata ) in Northeast Atlantic Inshore Fisheries

Abstract

Quantifying discard survival of species is crucial for effective fishery management. Electronic tags and visual health assessments were used to estimate postrelease survival of commercially caught thornback ray ( Raja clavata ), undulate ray ( Raja undulata ) and small‐eyed ray ( Raja microocellata ) from Northeast Atlantic inshore fisheries. Thornback ray were sampled in the English Channel trammel net fishery ( n = 60), the southern North Sea otter trawl ( n = 52) and longline ( n = 60) fisheries. Undulate ray ( n = 65) and small‐eyed ray ( n = 68) were sampled in the English Channel otter trawl fishery. Depth and temperature measurements logged on data storage tags were used to infer fish fate. Fish condition was assigned to ordinal classes of vitality, reflex impairment and injury ( n = 1480). Vitality data were combined with inferred fates of tagged skates to estimate fishery discard survival. For thornback rays, estimated survival was 94.3% in trammel nets, 97.0% in otter trawls and 75.1% on longlines. In otter trawl fisheries, estimated survival was 82.7% for undulate ray and 55.3% for small‐eyed ray. Estimates of discard survival have immediate application to support regulations permitting release of unwanted skates and for estimating population removals in stock assessments.

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