Movements and oceanographic associations of bigeye tuna ( Thunnus obesus) in the Northwest Atlantic

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Lam, Chi Hin, Galuardi, Benjamin, Lutcavage, Molly E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2014
• Subjects: Northwest Atlantic
• Online Access: http://dx.doi.org/10.1139/cjfas-2013-0511; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjfas-2013-0511; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfas-2013-0511

To address the lack of fisheries-independent information for Atlantic bigeye tuna (Thunnus obesus), we released 21 adults (131 ± 12 cm curved fork length) between 2008 and 2010 in the Sargasso Sea and Northwest Atlantic. Data from nine tags (range: 1–292 days; mean: 89 days) revealed (i) pronounced north–south movements in pelagic waters between areas including Georges Bank, Mid- and South Atlantic Bight, Caribbean Sea, and Brazilian shelf, (ii) a lack of east–west exchange, and (iii) a high-use area in the Hatteras Plain, centered southwest of Bermuda. Bigeye tuna occupied water masses of 2.7–28.2 °C and depths of 0–1280 m, with deeper depths in the daytime (daily mean ± standard deviation: 196 ± 92 m) than at nighttime (45 ± 29 m). Even though bigeye tuna are assumed to forage on the deep scattered layer during the day, generalized additive mixed models did not identify the deep scattered layer as an important predictor of daytime swimming depth. Model results highlight the importance of geographic location in influencing habitat utilization, and thus suggest the need for fisheries-independent monitoring in high-catch areas, such as the central and equatorial Atlantic.