Age and Growth of Larval Atlantic Bluefin Tuna, Thunnus Thynnus from The Gulf of Mexico.

Atlantic bluefin tuna (Thunnus thynnus) are the largest and most highly prized among the tuna (Scombridae) family. They are highly pelagic, undertaking transoceanic migrations throughout the Atlantic, but the main spawning grounds are the Mediterranean Sea and the Gulf of Mexico (GOM). Given their mobility, management for this species is handled through international agreements under the auspices of the International Committee for the Conservation of Atlantic Tuna (ICCAT) and within the United States, through the National Oceanic and Atmospheric Administration (NOAA). Despite 30 years of ichthyoplankton surveys in the GOM, little is known about larval bluefin tuna ecology with regards to growth and survival. Larvae were collected from plankton tows during the Spring Ichthyoplankton research survey using 1 x 2 m plankton nets (505 and 1000 µm mesh) towed in the upper 10 m of the water column in the GOM in April-May, 2012. Otoliths (sagittae and lapilli) were dissected from 100 larvae, ranging from 2.4 to 8.4 mm (NL or SL) and larval daily age was determined by examining otolith microstructure. Estimated ages ranged from 4 to 18 days and new growth curves for the GOM were compared with existing age estimates for bluefin tuna larvae. Growth was significantly different when compared to similar studies in the Florida Keys and in the Mediterranean Sea, but always highly variable at any given length. Environmental parameters examined significantly influenced larval growth. Results will improve the larval index for bluefin tuna by incorporating specimens collected from established spawning grounds. In addition, results will inform stock assessment and play a key role in developing predictive ecological models to enhance ecosystem based fisheries management in the region