Improve the purse-seine index of abundance for yellowfin tuna based on CPUE of purse-seine sets on dolphins

Project H.1.g - Improve the purse-seine index of abundance for yellowfin tuna based on CPUE of purse-seine sets on dolphins

09 Sep 2024 - 09 Sep 2027

Program(s) in charge: Stock Assessment Program

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Theme 3. Sustainable fisheries
Goal H. Improve and implement stock assessments, based on the best available science
Target H.1. Undertake the research necessary to develop and conduct at least one benchmark stock assessment for yellowfin and bigeye tunas

Objectives

Improve the yellowfin tuna stock assessment main index of abundance by understanding factors related to catch rates and length composition

Background

Since the 2020 benchmark assessment for yellowfin tuna, the main index of abundance is obtained from the CPUE of purse-seine sets on dolphin standardized using spatiotemporal models. The fisheries, however, have evolved over time, and changes in catchability may have occurred. Discussions with the fishing industry revealed that substantial changes in technology have occurred in the last 5 years. In addition, there is evidence that the length composition of tunas may differ according to the species of dolphin they are associated with. Finally, the external review panel indicated that the was no clear evidence that the index was an index of abundance of yellowfin rather than an index of the yellowfin-dolphin interaction.

Relevance for management

The yellowfin tuna stock assessment main piece of information is the index derived from the purse-seine fisheries with sets associated with dolphins. Improvements in the index will reflect in the yellowfin assessment, which will make the staff’s scientific advice more accurate and precise.

Duration

2024-2027

Workplan and status

List potential variables that can change catchability including code groups and changes in technology.
Exploratory data analysis
Modelling

External collaborators

Purse-seine fishing industry that operates with purse-seine sets on dolphins

Deliverables

Report(s) to SAC in 2026, 2027