Atlantic bluefin tuna Thunnus thynnus feeding ecology in the northern Gulf of Mexico: a preliminary description of diet from the western Atlantic spawning grounds.

A combination of stomach contents, nitrogen stable-isotope and tissue C:N values are presented to demonstrate feeding activity of Atlantic bluefin tuna Thunnus thynnus on the Gulf of Mexico (GOMEX) spawning grounds. Diets include teleosts, cephalopods, crustaceans and a pelagic tunicate (Pyrosoma atlanticum). Results reveal the need to classify the GOMEX as a T. thynnus feeding ground.

Overlap between Atlantic bluefin tuna spawning grounds and observed Deepwater Horizon surface oil in the northern Gulf of Mexico.

The 2010 Deepwater Horizon oil spill impacted the northern Gulf of Mexico (GOM) during the spring spawning season of Atlantic bluefin tuna (BFT). Overlap between BFT spawning habitat and surface oil in the northern GOM was examined using satellite-derived estimates of oil coverage, and spawning habitat models. Results suggested that although eggs and larvae were likely impacted by oil-contaminated waters in the eastern GOM, high abundances of larvae were located elsewhere, especially in the western GOM. Overall, less than 10% of BFT spawning habitat was predicted to have been covered by surface oil, and less than 12% of larval BFT were predicted to have been located within contaminated waters in the northern GOM, on a weekly basis. Our results provide preliminary but important initial estimates of the effects of the spill on larval BFT mortality, as concern continues over the appropriate management responses to impacts of the spill.

Size and age estimates at sexual maturity for the little skate Leucoraja erinacea from the western Gulf of Maine, U.S.A.

Size and age estimates at sexual maturity were determined for 162 male and 273 female little skates Leucoraja erinacea collected from the western Gulf of Maine. Maturity ogives suggest that 50% maturity in females occurs at age 9.5 years and 480 mm total length (LT), whereas 50% maturity in males occurs at a slightly younger age of 7.7 years and smaller size of 460 mm LT. Age estimates were made from 389 L. erinacea ranging in size from 93 to 570 mm LT. The index of average per cent error and age-bias plots indicated that the ageing methods were precise and non-biased. Additionally, annual periodicity of band formation was validated with oxytetracycline in eight individuals (three males and five females) ranging in age from 3 to 12 years. In conclusion, results from this study indicate that L. erinacea exhibits characteristics that make other elasmobranch populations highly susceptible to overexploitation.