Abstract

Summer ichtyoplankton surveys were conducted in the northern Gulf of Mexico (GoM) from 2007 - 2010, and catch data were used to characterize patterns of distribution and abundance of tuna larvae (Thunnus spp.) within this region. High resolution melting analysis was performed on a subset of samplesto determine the species composition of Thunnus larvae in our collections and four different species were observed: blackfin tuna Thunnus atlanticus (89%), yellowfin tuna T.albacares (7%), bluefin tuna T.thynnus (4%), and bigeye T. Obsesus (< 1). Overall, 12,674 larvae in the genus Thunnus were collected and mean density and percent frequency of occurrence of larvae was 0.98 larvae 1000 m-3 and 78.5%, respectively. Intra- and inter-annual variability in catch numbers of tuna larvae were observed with the lowest density present in June (0.51 larvae 1000/m3) and in 2010 (0.42 larvae 1000/m3), the summer following the Deepwater Horizon oil spill. Oceanographic conditions influenced catch numbers of tuna larvae and our results indicate that mesoscale features and physicochemical characteristics of water masses affect the distribution and abundance of tuna larvae. Response plots from a generalized additive models (GAMs) indicated that densities of tuna larvae were higher near fronts of mesoscale oceano-graphic features (Loop Current and eddies), and in high salinity and lower temperature water masses typically found in outer shelf and slope waters of the GoM.

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