Pelagic Habitat Partitioning of Late-Larval and Juvenile Tuna in the Oceanic Gulf of Mexico
Gulf of Mexico Oil Spill and Ecosystem Science Conference / Tampa Bay, Florida
Tunas are ecologically important in pelagic ecosystems, but due to their high economic value, most species are overfished. Declines in fishery landings of large-bodied tuna species in the Gulf are expected to increase fishing pressures on unmanaged, small-bodied tuna species, whose life history traits are less known. While predicting spawning stocks and recruitment success typically focuses on estimates of larval abundances, juveniles may provide a better estimate of future adult stock sizes, as they are more likely to survive to adulthood. However, distributional studies on juveniles are rare, leading to a gap in our understanding of tuna ecology. In the present study, tuna early life stages were collected across the Gulf between 2010-2011 (NRDA ONSAP) and between 2015-2018 (DEEPEND). The size class examined in this study, representing large larvae and small juveniles, is larger than that of previous larval tuna studies in the Gulf. In total, 11 of the 16 scombrid species inhabiting the Gulf were collected, with small-bodied tuna species (Euthynnus alletteratus [little tunny] and Thunnus atlanticus [blackfin tuna] dominating the assemblage. Generalized additive models and distributional plots indicated that early life stages of E. alletteratus were associated with productive continental shelf/slope environments (low salinity, high chlorophyll a concentrations, nearer to shelf break), while T. atlanticus juveniles were associated with oligotrophic habitats (high salinity, low chlorophyll a concentrations, further from shelf break). These results demonstrate that over a broad spatiotemporal domain, large larvae and juvenile tunas partition pelagic habitat on the mesoscale in addition to the temporal partitioning of adult spawning. These factors are important for spatially and temporally explicit modeling aimed at predicting tuna stock sizes, and for assessing the spatial vulnerability of small tunas to oil spill events.
Pruzinsky, Nina; Milligan, Rosanna; and Sutton, Tracey, "Pelagic Habitat Partitioning of Late-Larval and Juvenile Tuna in the Oceanic Gulf of Mexico" (2020). Marine & Environmental Sciences Faculty Proceedings, Presentations, Speeches, Lectures. 687.