Abstract
BackgroundThe salmon shark (Lamna ditropis) is a widely distributed apex predator in the North Pacific Ocean. Many salmon sharks from the eastern North Pacific, specifically Prince William Sound, Alaska, have been satellite tagged and tracked, but due to the sexual segregation present in salmon sharks, most of these tagged sharks were female. Consequently, little information exists regarding the migration patterns of male salmon sharks. To better understand the migration and distribution of this species, information on the male component of the population as well as from sharks outside of Prince William Sound, Alaska, is needed. In this study, we deployed satellite transmitters on two mature male salmon sharks caught in the Bering Sea.ResultsThe two mature male salmon sharks tagged in the Bering Sea exhibited distinct migration patterns. The first male, tagged in August 2017, traveled to southern California where it remained from January to April after which it traveled north along the United States’ coast and returned to the Bering Sea in August 2018. The second male, tagged in September 2019, remained in the North Pacific between 38° N and 50° N before returning to the Bering Sea in July of year one and as of its last known location in year two. The straight-line distance traveled by the 2017 and 2019 sharks during their 12 and 22 months at liberty was 18,775 km and 27,100 km, respectively.ConclusionsBefore this study, our understanding of salmon shark migration was limited to female salmon sharks satellite tagged in the eastern North Pacific. The 2017 male salmon shark undertook a similar, but longer, north–south migration as tagged female sharks whereas the 2019 shark showed little overlap with previously tagged females. The different migration patterns between the two male sharks suggest distinct areas exist for foraging across the North Pacific. The return of both sharks to the Bering Sea suggests some fidelity to the region. Continued tagging efforts are necessary to understand the population structure of salmon sharks in the North Pacific. This tagging study highlights the importance of opportunistic efforts for obtaining information on species and sex with limited distribution data.
Highlights
The salmon shark (Lamna ditropis) is a widely distributed apex predator in the North Pacific Ocean
Salmon sharks are strongly separated by sex, with female dominance in the eastern North Pacific (ENP) and male dominance in the western North Pacific (WNP) [7, 16], and previous satellite tagging work has only been conducted within the ENP, Prince William Sound, Alaska, which almost exclusively tagged female salmon sharks [4, 17,18,19]
Estimated geolocations and corresponding error polygons derived from the Hidden Markov model (HMM, see Section “Data filtering and analysis” in total length (TL)/pre-caudal length (PCL) length (m) Tag model
Summary
The salmon shark (Lamna ditropis) is a widely distributed apex predator in the North Pacific Ocean. Many salmon sharks from the eastern North Pacific, Prince William Sound, Alaska, have been satellite tagged and tracked, but due to the sexual segregation present in salmon sharks, most of these tagged sharks were female. We deployed satellite transmitters on two mature male salmon sharks caught in the Bering Sea. The salmon shark (Lamna ditropis [1]) is a widely distributed apex predator found in the coastal and oceanic waters of the North Pacific Ocean (NPO), from the Bering Sea to the Sea of Japan in the western North Pacific (WNP) and from the Gulf of Alaska to Baja California, Mexico, in the eastern North Pacific (ENP) [2, 3].
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