Putative mating behavior in basking sharks off the Nova Scotia coast

We report aerial observation of 13 basking sharks (Cetorhinus maximus) enga ged in putative mating behavior near the ocean surface 21 June 1998 at appr oximately 1230 AST, 140.8 km from the Nova Scotia mainland in the North Atl antic at 44 degrees 16'N, 61 degrees 38'W, depth 130 m. Video and photo doc umentation showed the 68 m long sharks, some with discrete white patches on the dorsum and appendages, swimming slowly clockwise in a tight circle wit h many animals closely associated with up to three other animals. Previousl y described behaviors and motor patterns consistent with elasmobranch repro duction including "parallel swimming," possible "pectoral biting," "nudging ," and "male on top of female" were seen as well as other behaviors, includ ing nose-to-tail following; flank approach; close approach involving rostra l contact or proximity with the gill, pectoral fin, vent, and dorsum; and e chelon swimming. Behaviors involving close and persistent physical associat ion of two or more animals and the persistence of the circling behavior in a circumscribed area over a period in excess of 5 min indicated that this m ay represent the first well-documented observation of group courtship behav ior in basking sharks.