Open AccessConnecting post-release mortality to the physiological stress response of large coastal sharks in a commercial longline fishery
Author(s) -
Nicholas M. Whitney,
Karissa O. Lear,
John Morris,
Robert E. Hueter,
John K. Carlson,
Heather Marshall
Publication year - 2021
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0255673
Subject(s) - carcharhinus , fishery , biology , bycatch , tiger , population , leucas , fishing , medicine , computer security , environmental health , computer science
Bycatch mortality is a major factor contributing to shark population declines. Post-release mortality (PRM) is particularly difficult to quantify, limiting the accuracy of stock assessments. We paired blood-stress physiology with animal-borne accelerometers to quantify PRM rates of sharks caught in a commercial bottom longline fishery. Blood was sampled from the same individuals that were tagged, providing direct correlation between stress physiology and animal fate for sandbar ( Carcharhinus plumbeus , N = 130), blacktip ( C . limbatus , N = 105), tiger ( Galeocerdo cuvier , N = 52), spinner ( C . brevipinna , N = 14), and bull sharks ( C . leucas , N = 14). PRM rates ranged from 2% and 3% PRM in tiger and sandbar sharks to 42% and 71% PRM in blacktip and spinner sharks, respectively. Decision trees based on blood values predicted mortality with >67% accuracy in blacktip and spinner sharks, and >99% accuracy in sandbar sharks. Ninety percent of PRM occurred within 5 h after release and 59% within 2 h. Blood physiology indicated that PRM was primarily associated with acidosis and increases in plasma potassium levels. Total fishing mortality reached 62% for blacktip and 89% for spinner sharks, which may be under-estimates given that some soak times were shortened to focus on PRM. Our findings suggest that no-take regulations may be beneficial for sandbar, tiger, and bull sharks, but less effective for more susceptible species such as blacktip and spinner sharks.