Survival and recovery of three shark species in North-East Atlantic recreational fisheries

Understanding how sharks respond to catch and release (C&R) recreational fisheries is an important requirement for effective management. Post-release survival and recovery in recreational fisheries can be species- and setting-dependent. Nevertheless, no study on sharks has been conducted in European recreational fisheries, despite their popularity as target. This study presents the first example of biologging to assess C&R effects on blue sharks (Prionace glauca), porbeagle sharks (Lamna nasus) and tope sharks (Galeorhinus galeus) in the UK. Pop-up satellite archival tags (n = 23 blue shark, 20 porbeagle shark, 26 tope shark) revealed high (94.7–96.2%) survival rates in all three species, with one case of mortality in each. Mortalities could not be definitively attributed to any one aspect of the capture event, as the three animals that died were free of external wounds, and energetic upon release. However, two dead individuals (a porbeagle and a tope shark) were deep hooked and released with hooks in place, which may have caused internal injuries undetectable to observers. Depth time-series data from recovered tags (n = 16) were used to infer when sharks had recovered from angling through changepoint analysis of four movement metrics. Most individuals appeared to recover by 24 hours post-release. Prior to this, abnormal behaviour varied between- and within-species, though typically involved depth-holding either mid-water or near the seafloor, and lower vertical speed. These data offer insights into the behaviour of electronically tagged sharks immediately post-release. The results suggest that when C&R fishing is conducted in accordance with current best-practice guidelines, post-release survival of the three studied shark species can be high.