ABSTRACT
Seasonal variation in harbour porpoise distribution has been described as a general inshore movement in summer and offshore movement in winter, although east-west and north-south migrations have also been proposed in different locations (e.g. Tomilin 1957, Gaskin et al. 1974, Gaskin 1977, 1984, Taylor & Dawson 1984, Gaskin & Watson 1985, Northridge et al. 1995, Read & Westgate 1997). Seasonal movements are believed to be related to prey availability or to breeding habitat (Gaskin 1977, Northridge et al. 1995, Read & Westgate 1997). Camphuysen & Leopold (1993) interpreted the higher numbers of porpoise sightings and strandings on the Dutch coast in winter than in summer as indicating a seasonal east-west movement.
