Organochlorine residues in harbour porpoise and bottlenose dolphins stranded on the coast of Scotland, 1988-1991.

The organochlorine (OC) residues, chlorobiphenyls (CBs), DDT and its metabolites, dieldrin, hexachlorobenzene and technical chlordane mixtures have been determined in the blubber of harbour porpoise and bottlenose dolphins from around the north and east coasts of Scotland as a result of strandings and bycatches between 1988 and 1991. The concentrations of OCs range from some of the lowest values reported at 280 micrograms kg-1 for t-CBs, 145 micrograms kg-1 for t-DDT and 71 micrograms kg-1 for dieldrin to some of the highest values, 23,000 micrograms kg-1 for t-CBs, and 10,200 micrograms kg-1 for t-DDT. OC levels were correlated with the age and sex of the sample of harbour porpoise and bottlenose dolphins from the Moray Firth area. The study confirms that the concentration of these compounds is highly dependent on co-factors of age and sex, and that data from single or small numbers of animals may be of limited value in comparing information on organochlorine residues in mammals within or between regions.