Relationship between the characteristics of purse-seine vessels and fishing mortality (Project J.2.A): Progress Report

Lopez J, Lennert-Cody C, Maunder M, Altamirano E (2019) Relationship between the characteristics of purse-seine vessels and fishing mortality (Project J.2.A): Progress Report. In: IATTC - 10th Meeting of the Scientific Advisory Committee. IATTC-SAC-10-10, San Diego, California

The constantly increasing effort of the purse-seine fleet in the eastern Pacific Ocean (EPO) requires more stringent management measures to conserve the stocks of tropical tunas. Extending the closures of the fishery, from the 1999 ban on sets on floating objects to the current 72 days of total closure, has been difficult for the Members of the Commission. Sometimes, additional measures have been tried as alternatives to adding more days to the closure, such as catch limits by set type in 2017, and limiting the number of active fish-aggregating devices (FADs) per vessel in 2018. Nevertheless, the current tuna conservation measure (Resolution C-17-02) may not be as effective as desired, and new and different measures may be required.

As such, the staff has recently received a growing number of requests for further analyses of alternative management measures. Also, using vessel well volume as the measure of fleet capacity when determining the days of closure needed to meet a conservation target is somewhat simplistic, and a more precise measure of capacity, and of the relationship between capacity and fishing mortality, needs to be quantified. In addition, the relationship between catches and the number of FADs deployments, active FADs, FAD history, environment, and technology, needs to be better understood. The staff has conducted some preliminary analyses in the past, but did not have the time or resources to undertake the in-depth investigations necessary to meet these requests. Therefore, a full-time researcher was hired in early 2018 for two years to address six related questions, requiring quantitative analysis, that were grouped into one project (J.2.a) in the Strategic Science Plan (SSP). This document describes the progress achieved during the first year of the project and presents the plan for the second year (Appendix 1), and outlines current needs and interactions with other projects of interest for the Commission.