Large numbers of harbor porpoises are caught in fishing nets, because the porpoises feed on schooling fish such as herring and mackerel, in relatively shallow coastal waters. They are also affected by increasing pollution in coastal waters, and are considered vulnerable or threatened in many parts of their range. They are social, and feed in groups, working their way northward to spend the summer in cooler waters and back south as far as Los Angeles, in the Pacific, and the Carolinas or even Florida, in the Atlantic, for the winter. These small, stocky animals breed when they are 3-5 years old. Females nurse their calves for about 9 months. The stomachs of 4-5 month old juveniles killed in gillnets contained both milk and solid food, which indicates that they were beginning to feed themselves.
Links:Mammal Species of the WorldClick here for The American Society of Mammalogists species account
Original description: Linnaeus, C., 1758. Systema Naturae per regna tria naturae, secundum classis, ordines, genera, species cum characteribus, differentiis, synonymis, locis. Tenth Edition, Laurentii Salvii, Stockholm, 1:77, 824 pp.