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Pelagic food web realignment supports resilient larvae of Southern Bluefin Tuna in a warming ocean
Journal article   Open access   Peer reviewed

Pelagic food web realignment supports resilient larvae of Southern Bluefin Tuna in a warming ocean

Michael R Landry, Raúl Laiz-Carrión, Estrella Malca, Rasmus Swalethorp, Moira Décima, José M Quintanilla, Ricardo Borrego-Santos, Claire H Davies, Sven A Kranz, Karen E Selph, …
Proceedings of the National Academy of Sciences - PNAS, Vol.123(35), e2601583123
2026
DOI: https://doi.org/10.1073/pnas.2601583123
PMID: 42636360
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Published2.36 MBDownloadView
Published (Version of Record) Open Access CC BY V4.0

Abstract

larval tuna appendicularian larvacean feeding growth
Significance Most trophic complexities are unconsidered in models that predict future ocean states, and critical interactions may also be poorly represented in historical knowledge. Comparing studies done 35 y apart, feeding and growth of Southern Bluefin Tuna larvae significantly improved due to a shift to a narrow diet of appendicularians, departing from the long-established trends of broad diet and crustacean prey for bluefin species. We make the case that appendicularians are the most efficient prey resource for bluefin larvae and will be environmentally selected as warming waters become less productive and dominated by small phytoplankton. As environmental conditions are altered, trophic adaptations within complex food webs can lead to substantially different species outcomes than expected from simple models and historical trends. Abstract Many of the oceans’ top predatory fishes at low to mid latitudes face an uncertain future as their vulnerable larvae deal with higher environmental temperature and reduced productivity associated with climate change. However, ocean ecosystem models that predict a general decline of zooplankton prey with warming and stratification hardly ever account for complexities in pelagic food webs that might make them resilient in providing food resources for larvae. We illustrate such complexities in comparing feeding interactions of larval Southern Bluefin Tuna (SBT) between two studies conducted 35 y apart in the same spawning region off northwest Australia. In the first (1987), SBT larvae fed and grew at low rates demonstrably limited by zooplankton prey. In the second (2022), feeding and growth were significantly higher despite substantially warmer conditions. The difference reflects a realignment in larval feeding preference from copepods to appendicularians, which allows a more direct and efficient energy transfer pathway from the microbially dominated food web base to higher-level consumers. These findings reset thinking on bluefin larvae feeding preferences, demonstrate high growth on an appendicularian diet up to 30 °C, and align with predictions of appendicularians being an environmentally selected zooplankton category in warming oligotrophic waters.

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UN Sustainable Development Goals (SDGs)

This output has contributed to the advancement of the following goals:

#14 Life Below Water

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