Publication Abstract

Metals and organochlorines in sperm whales (Physeter macrocephalus) stranded around the North Sea during the 1994/95 winter

R.J. Law, R.L. Stringer, C.R. Allchin and B.R. Jones

During the winter of 1994/1995, some 21 sperm whales (Physeter macrocephalus) were stranded around the North Sea, on the coasts of the United Kingdom, Germany, Belgium and The Netherlands. This is an abnormally high number of strandings to occur on North Sea coasts. In both 1988 and 1990 32 sperm whales were stranded, but these were generally on the Atlantic coasts of the British Isles and Norway, rather than North Sea coasts (Berrow et al., 1993). Evans (1992) has recorded a clear increase both in strandings of sperm whales on British and Irish coasts this century, and in sightings of groups of animals (rather than lone individuals) to the west of the British Isles. Both sightings and strandings of sperm whales between 1967 and 1990 were concentrated around Shetland, Orkney and the outer Hebrides, suggesting that their main approach to the land mass is from the north-west (Sheldrick et al., 1991). Sperm whales are oceanic animals which rarely enter shallow or semi-enclosed areas of the sea, and are thought to approach close to shore only when sick (Martin, 1990). Females and immature animals remain in low latitudes, and only mature males venture into latitudes higher than about 40-45° in both hemispheres. In most areas, sperm whales feed almost exclusively on cephalopods (squid and octopus), although in a few areas, fish form an important component of their diet. For instance, close to the coast of Iceland, sperm whales were found to have been feeding primarily on deep-sea fish such as lumpsuckers, angler fish and red-fish which are found to depths of 500 m or more (Martin & Clarke, 1986). Prey are usually taken in midwater at depths greater than 400 m, although some bottom feeding also occurs. In the North Atlantic, sperm whales feed on the Grand Banks off Newfoundland, as well as on the continental slope to the west of the British Isles, and north towards Iceland (Evans, 1987; Martin, 1990). Male sperm whales may not find it easy to feed successfully in the shallow waters of the North Sea, which in the central and southern areas are less than 100 m in depth (A. R. Martin, pers. comm.).

Reference:

R.J. Law, R.L. Stringer, C.R. Allchin and B.R. Jones, 1996. Metals and organochlorines in sperm whales (Physeter macrocephalus) stranded around the North Sea during the 1994/95 winter. Marine Pollution Bulletin, 32: 72-77.