Postrelease survival of silky sharks (<i>Carcharhinus falciformis</i>) following capture by longline fishing vessels in the equatorial eastern Pacific Ocean

Abstract

Domestic longline fishing fleets of Costa Rica and Ecuador commonly target and retain sharks. For this study, a handling method recommended by the fishers of those fleets to optimize postrelease survival (PRS) was evaluated. The PRS rate estimated from Kaplan–Meier survival analyses was 94.3% (95% CI: 87.0%–100%) for 38 silky sharks, Carcharhinus falciformis (Muller and Henle, 1839), captured by longline fishing vessels of Costa Rica and Ecuador in the equatorial eastern Pacific Ocean following tagging and release with pop-up satellite archival tags (PSATs). The 36 C. falciformis survivors were at liberty with PSATs attached for an average of 100.6 d (range: 5–180 d) in an area of relatively high fish-aggregating device (FAD) density, and during that period none of those sharks became entangled in netting suspended beneath FADs. Average linear displacements for 29 C. falciformis at liberty for >30 d was 578.8 nautical miles (range: 81.7–1725.0 nautical miles) indicating relatively widespread dispersion from release locations.