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The global range of Risso's dolphin Grampus griseus is not well known, and there has been confusion in the literature as to whether the species has a broad, circumglobal range or only occurs along continental margins., To clarify the species' distribution and habitat preferences, we compiled and reviewed all available (published and unpublished) records of sightings and captures of this species for the past 62 years (1950-2012, n = 8068 records). Stranding records were not included., The results showed that the species has a range that extends across ocean basins and spans between at least 64°N and 46°S, and is apparently absent from high-latitude polar waters. Although Risso's dolphins occur in all habitats from coastal to oceanic, they show a strong range-wide preference for mid-temperate waters of the continental shelf and slope between 30° and 45° latitude., Although a number of misconceptions about the distributional ecology of Risso's dolphin have existed, this analysis showed that it is a widespread species. It strongly favours temperate waters and prefers continental shelf and slope waters to oceanic depths. These habitat preferences appear to hold throughout much or all of the species' range. [ABSTRACT FROM AUTHOR]

ABSTRACT 1. The Clymene dolphin Stenella clymene is found in tropical and warm temperate waters of both the North and South Atlantic Oceans. Confusion surrounding the identifying characteristics of this species has contributed to a general lack of knowledge of this species. 2. We collected and verified a total of 195 records (109 sightings, 67 strandings, and 19 captures) of Clymene dolphins. Twenty-five per cent (n = 49) of these records were previously unpublished. Rejected records are discussed in order to clarify the literature. 3. The northernmost locations for the Clymene dolphin are 39°17′N, 74°35′W (NJ, USA) and 19°1.9′N, 16°13.5′W (113 km north of Nouakchott, Mauritania). The southernmost locations are 29°58′S, 50°07′W (Tramandaí, Rio Grande do Sul, Brazil) and 3°40′S, 18°5′W (off Ascension Island). 4. Clymene dolphins were found in waters with bottom depths ranging from 44 to 4500 m (mean = 1870 m; SE = 110 m; median = 1675 m; n = 94). A single sighting reported at a location with a bottom depth of 44 m is considered to be atypical, as this species has an otherwise exclusively oceanic distribution. 5. Group sizes ranged from at least one individual in a mixed-species school of spinner dolphins Stenella longirostris to a group of an estimated 1000 animals (mean = 76.1; SE = 11; median = 47; n = 105). Stranding group size ranged from 1 to 46 individuals (n = 67), with single individuals being most common (n = 60). There is information available for seven mass strandings, all of which occurred in the south-eastern USA. [ABSTRACT FROM AUTHOR]