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1. Trophic specialization enhances growth performance in larvae of southern bluefin, albacore, and skipjack tunas from the eastern Indian ocean

   https://doi.org/10.1016/j.dsr2.2025.105585  

   Laiz-Carrión, Raúl; Borrego-Santos, Ricardo; Quintanilla, José María; Romegialli, Claudio Quezada-; Malca, Estrella; Swalethorp, Rasmus; Abascal, Francisco; Pennino, María Grazia; Vargas-Yáñez, Manuel; Johnstone, Carolina; et al (February 2026, Deep Sea Research Part II: Topical Studies in Oceanography)

   We examined trophic ecology and its influence on larval growth variability for three scombrids, southern bluefin (Thunnus maccoyii, SBT), albacore (T. alalunga, ALB), and skipjack tunas (Katsuwonus pelamis, SKJ), that share a common spawning ground in the eastern Indian Ocean. We combined otolith-based ageing with bulk nitrogen and carbon stable isotope analysis (SIA) of individual larva. Significant interspecific differences in δ15N and δ13C indicate adaptive resource partitioning that allows these tunas to coexist during early ontogeny. Trophic position and isotopic niche were estimated with both frequentist and Bayesian approaches, enabling the evaluation of ontogenetic isotope shifts, niche overlap, and resource use in relation to growth. ALB grew fastest, had the highest trophic position, and the broadest isotopic niche. Optimally growing tuna larvae occupied the narrowest trophic niche and had lower trophic positions for all three species, supporting the hypothesis that strong trophic specialization supports better growth performance and that feeding on more efficient shorter food chains (e.g., microbial loop via appendicularians) can enhance larval fitness. Using lower C:N ratio as a proxy of larval condition found in optimal growing groups supports the broader hypothesis that growth potential is closely tied to energy allocation strategies during early ontogeny. A detailed understanding of how larval trophodynamics, niche breadth, and resource partitioning interact with growth and survival during these vulnerable stages is essential for ecosystem-based management, particularly in systems where growth rate modulates predation risk and competitive fitness. 

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2. Maternal Effects and Trophodynamics Drive Interannual Larval Growth Variability of Atlantic Bluefin Tuna (Thunnus thynnus) from the Gulf of Mexico

   https://doi.org/10.3390/ani14091319  

   Quintanilla, José M; Borrego-Santos, Ricardo; Malca, Estrella; Swalethorp, Rasmus; Landry, Michael R; Gerard, Trika; Lamkin, John; García, Alberto; Laiz-Carrión, Raúl (May 2024, Animals)

   none (Ed.)

   Two cohorts of Atlantic bluefin tuna (Thunnus thynnus) larvae were sampled in 2017 and 2018 during the peak of spawning in the Gulf of Mexico (GOM). We examined environmental variables, daily growth, otolith biometry and stable isotopes and found that the GOM18 cohort grew at faster rates, with larger and wider otoliths. Inter and intra-population analyses (deficient vs. optimal growth groups) were carried out for pre- and post-flexion developmental stages to determine maternal and trophodynamic influences on larval growth variability based on larval isotopic signatures, trophic niche sizes and their overlaps. For the pre-flexion stages in both years, the optimal growth groups had significantly lower δ15N, implying a direct relationship between growth potential and maternal inheritance. Optimal growth groups and stages for both years showed lower C:N ratios, reflecting a greater energy investment in growth. The results of this study illustrate the interannual transgenerational trophic plasticity of a spawning stock and its linkages to growth potential of their offsprings in the GOM. 

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3. Revisiting daily growth and survival insights of Southern Bluefin Tuna (Thunnus maccoyii) larvae in the eastern Indian Ocean

   https://doi.org/10.1016/j.dsr2.2025.105572  

   Borrego-Santos, Ricardo; Quintanilla, José M; Laiz-Carrión, Raúl; García, Alberto; Malca, Estrella; Abascal, Francisco J; Die, David; Riveiro, Isabel; Swalethorp, Rasmus; Landry, Michael R (February 2026, Deep Sea Research Part II: Topical Studies in Oceanography)

   This study analyzed the growth patterns and survival of Southern bluefin tuna (SBT, Thunnus maccoyii) larvae collected during January–February 2022 in their only known spawning area in the eastern Indian Ocean (IO). Otolith microstructure was examined to characterize both population-level and intra-population growth (OPToptimal and DEF-deficient group), with special emphasis on the flexion process, as well as to provide insights into larval survival. SBT larvae began flexion at sizes and ages comparable to those reported in other bluefin tuna species. At the intra-population level, OPT larvae reached flexion earlier in a better physical condition, with greater length, weight, and body depth, likely increasing their chances of survival at later stages. The observed larval growth rates (0.38 mm d−1) exceeded that from a historical study in 1987 (0.33 mm d−1), likely due to a ~2 ◦C increase in sea surface temperature and shifts in prey availability. Larval survival appears to depend on a selective process based on growth, in which only a small proportion of individuals (<2 %) exhibited width increment in otoliths similar to those of surviving larvae, allowing for faster development and earlier access to larger prey. These findings highlight the need for expanded research on the early life stages of SBT, particularly in the context of ongoing ocean warming and climate change. 

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4. Overview of BLOOFINZ/INDITUN investigations of the southern bluefin spawning region off northwest Australia, January–March 2022

   https://doi.org/10.1016/j.dsr2.2025.105564  

   Landry, Michael R; Laiz-Carrión, Raúl; Kranz, Sven A; Selph, Karen E; Stukel, Michael R; Malca, Estrella; Die, David; Beckley, Lynnath E; Décima, Moira; Swalethorp, Rasmus; et al (December 2025, Deep Sea Research Part II: Topical Studies in Oceanography)

   Not AvailabSouthern Bluefin Tuna (SBT, Thunnus maccoyii) range broadly in rich feeding grounds of the Southern Hemisphere but spawn only in a small tropical region off northwestern Australia directly downstream of the Indonesian Throughflow. Here, we describe goals, physical context, design and major findings of an end-to-end process study conducted during the peak SBT spawning season (January–March 2022) to understand nutrient sources, productivity, pelagic food web structure and their relationships to larval SBT feeding, growth and survival. Mesoscale variability was investigated by continuous underway measurements of surface waters and station sampling along the cruise track. Biogeochemical and community relationships, process rates, and trophic interactions were determined in four multi-day Lagrangian experiments in the southern Argo Basin. The study revealed strong system balances among nitrogen fluxes, phytoplankton production, grazing processes, and export. Highly selective feeding on appendicularians allows efficient trophic transfer from picophytoplankton-dominated production to SBT larvae. Plankton productivity, phytoplankton carbon and zooplankton biomass were proportionately elevated compared to similar measurements from the Atlantic bluefin larval habitat in the Gulf of Mexico, but with less advective input from the coastal margins. Individual-based otolith and stable isotope analyses identify larvae of lower trophic position, narrow diet, and narrow maternal diet as the fastest growers most likely to contribute to stock recruitment. Our study highlights the importance of system-level studies to document and understand the subtleties of how food webs of oligotrophic regions respond to climate change, which may not be predictable from the acquired knowledge of historical studies. 

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5. Active prey selection in developing larvae of Atlantic bluefin tuna ( Thunnus thynnus ) in spawning grounds of the Gulf of Mexico

   https://doi.org/10.1093/plankt/fbab020  

   Shiroza, Akihiro; Malca, Estrella; Lamkin, John T; Gerard, Trika; Landry, Michael R; Stukel, Michael R; Laiz-Carrión, Raúl; Swalethorp, Rasmus (April 2021, Journal of Plankton Research)

   Dolan, John (Ed.)

   Abstract Bluefin tuna spawn in restricted areas of subtropical oligotrophic seas. Here, we investigate the zooplankton prey and feeding selectivity of early larval stages of Atlantic bluefin tuna (ABT, Thunnus thynnus) in larval rearing habitat of the Gulf of Mexico. Larvae and zooplankton were collected during two multi-day Lagrangian experiments during peak spawning in May 2017 and 2018. Larvae were categorized by flexion stage and standard length. We identified, enumerated and sized zooplankton from larval gut contents and in the ambient community. Ciliates were quantitatively important (up to 9%) in carbon-based diets of early larvae. As larvae grew, diet composition and prey selection shifted from small copepod nauplii and calanoid copepodites to larger podonid cladocerans, which accounted for up to 70% of ingested carbon. Even when cladoceran abundances were <0.2 m−3, they comprised 23% of postflexion stage diet. Feeding behaviors of larvae at different development stages were more specialized, and prey selection narrowed to appendicularians and primarily cladocerans when these taxa were more abundant. Our findings suggest that ABT larvae have the capacity to switch from passive selection, regulated by physical factors, to active selection of presumably energetically optimal prey. 

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