Role of a Nematode in Natural Mortality of Spotted Dolphins

Parasitism was advanced by Delyamure (1955) as a major factor in the natural mortality of cetaceans, and infestation by helminths was implicated strongly as the cause of death in some stranded common dolphins (Delphinus delphis) (Ridgway and Dailey 1972). Severe and irreversible lesions of the skull of dolphins (Stenella spp.) caused by a nematode (Crassicauda sp.) were more prevalent among young animals than among old animals (Dailey and Perrin 1973). The reduced frequency of lesions with age indicated that severely infected animals were dying of the parasitic infection or a related cause (Dailey and Perrin 1973). We report quantification of mortality related to Crassicauda sp. in spotted dolphins (Stenella attenuata) in the eastern tropical Pacific.