Post-release survival of silky sharks (Carcharhinus falciformis) following capture by Mexican flag longline fishing vessels in the northeastern Pacific Ocean

Mexican flag longline fishing vessels operating in tropical waters of the northeastern Pacific Ocean commonly target and land silky sharks (Carcharhinus falciformis). In this study silky sharks captured by Mexican flag longline fishing vessels in the northeastern Pacific Ocean and brought onboard were tagged and released with pop-up satellite archival tags (PSATs), following removal of hooks or cutting gangions as close to the hook as feasible, to evaluate their post-release survival (PRS). The PRS rate estimated using Kaplan Meier survival analyses was 84.8 % (95 % CI: 71.0 %-100 %) for 63 silky sharks. Utilizing a rope noose to lift sharks aboard vessels was demonstrated to be an effective handling method. The 58 silky shark survivors were at liberty with PSATs attached for an average of 102 days (range: 1-298 d). Average linear displacement for 46 silky sharks at liberty for > 30 d was 512 nmi (range: 45-927 nmi), indicating relatively rapid widespread dispersion from release locations.

Automated summary

This study evaluated the post-release survival rate of silky sharks captured by Mexican longline fishing vessels in the tropical waters of the northeastern Pacific Ocean. The average post-release survival rate was found to be 84.8%, with a demonstration of an effective handling method using a rope noose to lift sharks aboard vessels. The survivors showed relatively rapid widespread dispersion from their release locations, with an average linear displacement of 512 nautical miles.