Catch reconstruction for the Indian Ocean blue shark: an alternative hypothesis based on rations

Citation
Coelho R, Rosa D (2017) Catch reconstruction for the Indian Ocean blue shark: an alternative hypothesis based on rations. In: IOTC - 13th Working Party on Ecosystems and Bycatch. IOTC-2017-WPEB13-22, San Sebastián, Spain
Abstract

The reconstruction of shark catch time series is particularly important for stock assessments, as the nominal catch data on sharks is usually very limited and a major source of uncertainty. This document provides an alternative hypothesis for the reconstruction of shark catches in the Indian Ocean (IOTC fisheries) based on a method developed for the EUPOA-Sharks (EU Plan of Action for Sharks). The estimation method is based on ratios of sharks:main species catches, obtained from observer programs, literature revision and/or personnel communications. In this paper we present the average estimations by fleet/métier for the Indian Ocean (2000-2015) as well as time series for 1971-2015. These time series (stock level) can be considered for use as alternative catch histories in the 2017 IOTC BSH stock assessment, both for production models (stock level estimations) and integrated models (fleet specific estimations).