Electronic tagging and population structure of Atlantic bluefin tuna


Electronic tags that archive or transmit stored data to satellites have advanced the mapping of habitats used by highly migratory fish in pelagic ecosystems1,2,3,4,5,6. Here we report on the electronic tagging of 772 Atlantic bluefin tuna in the western Atlantic Ocean in an effort to identify population structure. Reporting electronic tags provided accurate location data7,8,9 that show the extensive migrations of individual fish (n = 330). Geoposition data delineate two populations, one using spawning grounds in the Gulf of Mexico and another from the Mediterranean Sea. Transatlantic movements of western-tagged bluefin tuna reveal site fidelity to known spawning areas in the Mediterranean Sea. Bluefin tuna that occupy western spawning grounds move to central and eastern Atlantic foraging grounds. Our results are consistent with two populations of bluefin tuna with distinct spawning areas that overlap on North Atlantic foraging grounds. Electronic tagging locations, when combined with US pelagic longline observer and logbook catch data, identify hot spots for spawning bluefin tuna in the northern slope waters of the Gulf of Mexico. Restrictions on the time and area where longlining occurs would reduce incidental catch mortalities on western spawning grounds.

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Figure 1: Positions of Atlantic bluefin tuna electronically tagged at three western Atlantic locations (arrows) during 1996–2004.
Figure 2: Occurrence of Atlantic bluefin tuna on their western spawning ground in the Gulf of Mexico.
Figure 3: Movements over 4.5 years of one individual Atlantic bluefin tuna (603) that was tagged in the western Atlantic in 1999 and demonstrated site fidelity to a known spawning area in the Mediterranean Sea (2001–2003).
Figure 4: Seasonal distribution by size of Atlantic bluefin tuna that were tagged in the western Atlantic and measured before release.


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We thank R. Rinaldo, E. Prince, A. Seitz, T. Sippel, R. Schallert, N. Tulloch, G. Rosenwaks, S. Beemer, G. Shillinger, C. Perle, S. Vermillion, J. Bonaventura, D. Barber, M. Orbach, J. Jenkins, G. Stuve, P. Wright, D. Britt, B. Eakes, C. Perry, D. Brower, W. Whippen, R. Whorley, R. Jansenius, G. Sharp, R. Hill, T. Lindstrom, P. Ekstrom, P. Manuel, R. Ruais and S. Loga. We are indebted to the late Richard Novak for his contributions and sacrifice on behalf of the Tag-A-Giant programme. We thank the National Marine Fisheries Service (NMFS) for providing access to the GOM scientific observer data and US pelagic longline logbook data. The Tag-A-Giant programme was supported by grants and donations from the Packard, Pew, MacArthur, Disney, Marine Ventures, Gordon and Betty Moore, and Monterey Bay Aquarium Foundations. This research was supported in part by the NOAA NMFS, the NSF and the National Fish and Wildlife Federation. We acknowledge the extensive cooperation of the commercial and recreational captains and crews of fishing vessels in North Carolina, New England, Nova Scotia, Louisiana and Texas. We thank N. Miyabe of the National Research Institute of Far Seas Fisheries, ICCAT, A. Dinatale, G. DeMetrio, M. de la Serna and the EU COPEMED programme for return of electronic tags.

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Correspondence to Barbara A. Block.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Figure S1

Comparison of geoposition data from two types of electronic tags showing different spatio-temporal coverages obtained. (PDF 3750 kb)

Supplementary Figure S2

Movements of an individual western tagged Atlantic bluefin tuna (705) showing four years of subsequent fidelity to a spawning site in the Mediterranean Sea. (PDF 8603 kb)

Supplementary Figure S3

Figures showing distribution of Yellowfin tuna catch per unit effort (CPUE) in the Gulf of Mexico. (PDF 1266 kb)

Supplementary Figure Legends

Legends to accompany the above Supplementary Figures. (DOC 20 kb)

Supplementary Methods

This file contains supplementary information about methods for fishing operations, electronic tags and mixing. (DOC 33 kb)

Supplementary Table S1

Catch per unit effort (CPUE) and mortality per unit effort (MPUE) during scientific longline cruises in the Gulf of Mexico from 1998 to 2002. (DOC 42 kb)

Supplementary Table S2

Probability of Atlantic bluefin tuna being located in the western management unit after being tagged in the western Atlantic. (DOC 27 kb)

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Block, B., Teo, S., Walli, A. et al. Electronic tagging and population structure of Atlantic bluefin tuna. Nature 434, 1121–1127 (2005). https://doi.org/10.1038/nature03463

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