RISSO'S DOLPHIN (Grampus griseus): Western North Atlantic Stock

• Main Authors: Stock Definition, Geographic Range
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2000
• Subjects: Payne; Newfoundland; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.295.273; http://www.nmfs.noaa.gov/pr/pdfs/sars/ao2000dori-wn.pdf

Risso 's dolphin is distributed worldwide in tropical and temperate seas. Risso's dolphins generally have an oceanic range, and occur along the Atlantic coast of North America from Florida to eastern Newfoundland (Leatherwood et al. 1976; Baird and Stacey 1990). Off the northeast USA coast, Risso's dolphins are distributed along the continen tal shelf edge from C ape Hatteras northward to Georges Bank during the spring, summer, and autumn (CETAP 1982; Payne et al. 1984). In winter, the range begins at the mid-Atlantic big ht and ex tends furth er into oceanic waters (Payne et al. 1984). In general, the population occu pies the m id-Atlantic continental shelf edge year round, and is rarely seen in the Gulf of Maine (Payne et al. 1984). During 1990, 1991 and 1993, spring/summer surveys conducted in continental shelf edge and deeper oceanic waters had sightings of Risso's dolphins associated with strong bathymetric features, Gulf Stream warm-core rings, and the Gulf Stream north wall (Waring et al. 1992; W aring 1993). There is no information on stock differentiation of Risso's dolphin in the western North Atlantic. POPULATION SIZE Total numbers of Risso’s dolphins off the USA or Canadian Atlantic coast are unknown, although eight estimates from selected regions of the habitat do exist for select time periods. Sightings were alm ost exclusiv ely in the continental shelf edge and continental slope areas (Figure 1). An abundance of 4,980 Risso’s dolphins (CV=0.34) was estimated from an aerial survey