New assessment on accidentally captured silky shark post-release survival in the Indian Ocean tuna purse seine fishery

Source URL
https://iotc.org/documents/WPEB/1701/13
Citation
Onandia I, Grande M, Galaz JM, et al (2021) New assessment on accidentally captured silky shark post-release survival in the Indian Ocean tuna purse seine fishery. In: IOTC- 17th Working Party on Ecosystems & Bycatch (Data Prep). IOTC-2021-WPEB17(DP)-13_Rev1, Online
Abstract

Also published as WCPFC-SC17-2021/EB-IP-14.

A tagging experiment for Carcharhinus falciformis post-release survival assessment was conducted in a trip on-board the tuna purse seiner Jai Alai from Echebastar company in the Indian Ocean. Twenty-eight sharks were tagged with 24 SPATs and 4 MiniPATs and blood samples were collected in 45 sharks for lactate concentration measurement to be used as an indicator of shark survival. A vitality index based on state and behavior at release was also assigned to all the sharks caught accidentally. The overall predicted survival of silky shark in this trip was estimated to be 43%, both using survival rate by vitality index derived from tagged sharks and survival rate predicted using lactate concentration threshold. Shark survivorship decreased as the fishing operation advanced and vitality index declined. This information is essential to ensure the conservation of this vulnerable species and for a proper management of the fishery.