The first results of archival tagging of a basking shark, Cetorhinus maximus, in the western North Atlantic Little is known of the life history and ecology of the worldâs second largest fish, the basking shark (Cetorhinus maximus). In the western North Atlantic, this federally protected species is known to congregate in New England waters from May through October each year. To initiate a study of the 248 seasonal movements, behavior, and preferred habitat of the basking shark, a 6m female was tagged on September 27, 2001 with a pop-up satellite archival tag 73km east of Nantucket Island, Massachusetts. This animal belonged to an aggregation of approximately ten to twelve individuals swimming closely in a discrete area; none of the sharks was observed feeding. Although the tag was programmed to release in February 2002, the tag detached prematurely on December 6, 2001 in an area approximately 674km southwest of the tag site. The basking shark was vertically active for the entire tracking period, moving though depths and temperatures ranging from the surface to 320m and 5.8-21.0¼C, respectively. Over the 71 days, the shark displayed temporal variation in depth preference, with shallow behavior (<25m) more pronounced in late September, early October, and late November. Despite the wide range of water temperatures encountered, the behavior of the basking shark displayed a strong temperature preference, with 72% of the temperature observations in the narrow range of 15.0-17.5¼C. Although preliminary, this track provides evidence that the basking shark remains active and does not enter a hibernative state during the autumn months. (497: 6 July; Shawnee/Mission (AM); AES Life History & Movements)