Movement and environmental preferences of Greenland sharks (Somniosus microcephalus) electronically tagged in the St. Lawrence Estuary, Canada
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Three Greenland sharks (Somniosus microcephalus) were tagged with electronic tags, in Baie St. Pancrace, St. Lawrence Estuary, Quebec, Canada. One shark was tagged on 23 July 2004, with an acoustic telemetry tag. Two sharks were each tagged with a pop-up satellite archival tag (PSAT) on 27 August 2004. Two of the sharks remained in or close to the bay, one for 47 days and the other for at least 66 days. The third shark left the bay immediately after tagging on 27 August 2004. This shark entered the main channel of the St. Lawrence Estuary, and had moved 114.9 km upstream by 1 November 2004 when the tag reported to ARGOS satellites. The tags provided a total of 179 days of data on the movement and environmental preferences of Greenland sharks in the St. Lawrence Estuary. Sharks that reported depth and ambient water temperature data from the bay showed significant diel differences in depth preferences and corresponding ambient temperatures. The sharks remained near the bottom of the water column during the day and displayed increased vertical movements at night. The shark that resided in the main channel did not show this pattern, but generally remained at depths between 325 and 352 m. Sharks in the bay experienced water temperatures that ranged from −1.1 to 8.6°C at depths from 0 to 67 m. In the main channel the shark experienced temperatures that ranged from 1.0 to 5.4°C at depths from 132 to 352 m. This is the first report of numerous Greenland sharks inhabiting shallow near shore bays during summer and autumn.
KeywordsEnvironmental Preference Lawrence Estuary Greenland Shark Silky Shark Thresher Shark
All procedures were conducted under animal care protocols approved by the Dalhousie University committee on laboratory animals and field work was conducted under research license from the Department of Fisheries and Oceans, Canada. We thank S. Sirois, and the diving community of Baie Comeau PQ Canada. Acoustic tagging of the shark was performed by Jean-Yves Forest, under the supervision of J. G. with assistance from S. S. and A. Simard. Satellite tagging of sharks was performed by J.-Y. F., with assistance from S. S. and A. S. We thank F. Whoriskey and J. Carr of the Atlantic Salmon Federation, and G.L. Lacroix and D. Knox of the Department of Fisheries and Oceans for the lending of Vemco receivers. The manuscript was improved by comments from A. Ottensmeyer, R. O’Dor and K. Weng. This project was funded by the Future of Marine Animal Populations of the Sloan Foundation, Census of Marine Life (RAM); the Global Shark Assessment of the Pew Charitable Trust (RAM), and NSERC (RAM), and a Dalhousie fellowship to MJWS.
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