Age estimation and growth layer patterns in teeth of Commerson's dolphins (Cephalorhynchus c. commersonii) in subantarctic waters

Abstract

The Commerson’s dolphin, Cephalorhynchus c. commersonii, one of the world’s smallest cetaceans, occurs in the southwestern South Atlantic from about 41"30#S to near Cape Horn (56"S), including the central and eastern Strait of Magellan and the Falkland (Malvinas) Islands (Goodall 1978, Goodall et al. 1988). Along the coasts of Patagonia, northern Tierra del Fuego, Argentina, and the eastern Strait of Magellan, Chile, this is the cetacean most often seen near shore, where the animals feed and surf in the breakers. They seldom strand, but are commonly taken incidentally in shore-based gill nets set perpendicular to the coast over the wide tidal flats (Goodall 1978, 1994; Goodall et al. 1994, 2008; I˜n´ıguez et al. 2003). Although there have been few aerial surveys, this is probably the most abundant small cetacean in these waters and is the most affected by bycatch in artisanal fisheries.