Yellowfin Tuna Behavioural Ecology and Catchability in the South Atlantic: The Right Place at the Right Time (and Depth)

The yellowfin tuna ( Thunnus albacares: YFT) is a widely distributed, migratory species that supports valuable commercial fisheries. Landings of YFT are seasonally and spatially variable, reflecting changes in their availability accessibility to different fleets metiers which, turn, has implications for sustainable management. Understanding the dynamics behaviour how it affected by biological ecological factors therefore consequence fisheries management design. Archival pop-up satellite tags (PSAT) were used South Atlantic Ocean around St Helena between 2015 2020 collect information on movements, foraging locomotory YFT. study aimed (1) identify vertical within Helena’s EEZ; (2) assess timing depth potential feeding events (3) use inform catchability local pole line fishing fleet. Results indicate daytime shifted shallow with high incidence fast starts surface waters summer months (December April), deep strikes at colder (May November). Catchability was significantly reduced May November as spent more time depths below 100 m during day, which coincides reduction quantity caught inshore