Ocean Futures for the World’s Largest Yellowfin Tuna Population Under the Combined Effects of Ocean Warming and Acidification

Abstract

The impacts of climate change are expected to have profound effects on the fisheries of the Pacific Ocean, including its tuna fisheries, the largest globally. This study examined the combined effects of climate change on the yellowfin tuna population using the ecosystem model SEAPODYM. Yellowfin tuna fisheries in the Pacific contribute significantly to the economies and food security of Pacific Island Countries and Territories and Oceania. We use an ensemble of earth climate models to project yellowfin populations under a high greenhouse gas emissions (IPCC RCP8.5) scenario, which includes, the combined effects of a warming ocean, increasing acidification and changing ocean chemistry. Our results suggest that the acidification impact will be smaller in comparison to the ocean warming impact, even in the most extreme ensemble member scenario explored, but will have additional influences on yellowfin tuna population dynamics. An eastward shift in the distribution of yellowfin tuna was observed in the projections in the model ensemble in the absence of explicitly accounting for changes in acidification. The extent of this shift did not substantially differ when the three-acidification induced larval mortality scenarios were included in the ensemble; however, acidification was projected to weaken the magnitude of the increase in abundance in the eastern Pacific. Together with intensive fishing, these potential changes are likely to challenge the global fishing industry as well as the economies and food systems of many small Pacific Island Countries and Territories. The modelling framework applied in this study provides a tool for evaluating such effects and informing policy development.

Good fisheries management is good carbon management

“…The compounding effects of climate change and overfishing will disproportionately impact fisheries-dependent communities, increasing the economic vulnerability of small-scale fishers 78 and creating economic and food security challenges 79 . In addition to the environmental benefits, good fisheries management allows for the sustainable use of fish resources and ensures the socio-economic benefits of fishing.…”

Enhancing cooperative responses by regional fisheries management organisations to climate-driven redistribution of tropical Pacific tuna stocks

“…However, further improvements over past and recent SEAPODYM simulations and analyses (Lehodey et al, 2011;Lehodey et al, 2013;Lehodey et al, 2015;Bell et al, 2021) are needed to reduce uncertainty. These improvements should focus on: increasing the spatial resolution of the climate simulations model (currently operating at 2°of latitude and longitude); revising model parameter estimates at this higher resolution using updated fishing and tagging data to better inform tuna movement and habitat parameters (Senina et al, 2020b); and assessing key model uncertainties, including physical (e.g., influence of the Interdecadal Pacific Oscillation on the onset of accelerated ocean warming), biogeochemical (e.g., parameterisation of the microbial loop), or biological (e.g., effect of ocean acidification on mortality of larval stages, Frommel et al, 2016;Nicol et al, 2022) factors. The two RFMOs can also play a role in reducing uncertainty in ecosystem and tuna modelling through enlisting the assistance of industrial fishing vessels operating within their jurisdictions to collect additional data and information needed to verify and inform the modelling.…”

Age, growth, and mortality of Blackfin Tuna in the Gulf of Mexico

“…Atlantic Bluefin Tuna Thunnus thynnus and Southern Bluefin Tuna Thunnus maccoyii, Albacore Thunnus alalunga, Yellowfin Tuna Thunnus albacares, and Bigeye Tuna Thunnus obesus comprise some of the largest global fisheries (by landings and economic value), and their exploitation has led to population declines in different parts of the world (Juan-Jordá et al 2015;Bravington et al 2016;Braun et al 2023). In addition to direct removals, tuna populations are also threatened by the degradation of pelagic ecosystems due to pollutants, habitat alteration, and indirect changes in the functions and structure of ecosystems caused by overfishing and climate change (Nicol et al 2022;Braun et al 2023). While there is evidence to suggest that improved management actions over the past couple of decades have led to some recovery in tuna populations targeted by directed commercial fisheries (Juan-Jordá et al 2022), many smaller tuna species remain data poor and lacking assessment, preventing the development of similar management plans (Lucena-Frédou et al 2021).…”

“…In addition to direct removals, tuna populations are also threatened by the degradation of pelagic ecosystems due to pollutants, habitat alteration, and indirect changes in the functions and structure of ecosystems caused by overfishing and climate change (Nicol et al. 2022; Braun et al. 2023).…”