Award: OCE-1851395

Southern bluefin tuna (Thunnus maccoyii) is one of only three bluefin tuna species globally and is currently classified as Endangered on the IUCN Red List. Our project contributed critical new data from the 2022 spawning season in the only known reproductive grounds for this highly migratory species, filling key knowledge gaps in larval ecology. Updated estimates showed that larval growth is now slightly but significantly faster than estimates from the late 1980s, likely due to the higher sea surface temperatures that now prevail in the region. Stomach content analysis revealed that larvae were well-fed and showed a dietary preference for appendicularians when prey were abundant. Compared to analyses from the 1980s, this dietary shift may reflect an increase in energy transfer efficiency, supporting improved larval growth and survival.

These findings have implications that extend beyond science and technology. They directly inform the sustainability of southern bluefin tuna populations by connecting larval food-web dynamics and prey selectivity with broader biogeochemical pathways that support larval habitat quality under climate variability. By identifying differences in larval distribution, prey availability, and environmental conditions between waters with and without larvae, we have confirmed that this region functions as a critical larval habitat. This supports the potential for targeted spatial protections and ecosystem-based management in the region, contributing to conservation strategies for this endangered species.

Southern bluefin tuna support economically valuable fisheries, and understanding the factors that affect larval survival is key to forecasting recruitment, setting sustainable quotas, and securing long-term economic benefits for communities dependent on tuna fisheries. In addition, the project provides insight into how climate change is altering ocean productivity and trophic interactions, offering data that supports adaptation strategies for marine ecosystems and fisheries.

Beyond ecological and economic relevance, the project engaged the public through increased ocean literacy and generated multiple opportunities to build capacity in marine science. Students and early-career researchers participated in field sampling, laboratory experiments, and advanced analytical techniques such as compound-specific isotope analysis, gaining hands-on experience and interdisciplinary training. These experiences fostered career development in marine science and contributed to a more informed, capable, and diverse STEM workforce.

Last Modified: 08/20/2025
Modified by: Estrella Malca