CONCENTRATIONS OF SOME ORGANOCHLORINES IN OTTERS (LUTRA-LUTRA L) IN SCOTLAND - IMPLICATIONS FOR POPULATIONS

The concentrations of polychlorinated biphenyls (PCBs) and residues of organochlorine pesticides (HEOD and DDE) were measured in livers of o tters (Lutra lutra) from different areas in Scotland. Whilst HEOD and DDE occurred at very low concentrations only, PCBs were present in hig h levels in some areas, the highest in Shetland (geom mean 2.05 ppm we t wt), related probably to high levels in sediments in the north-east Atlantic. PCBs were a mixture of congeners in which higher-chlorinated ones predominated, especially 138, 153, 170 and 180, a pattern compar able to that observed in otters from continental Europe. Individual va lues of total PCB reached levels of over 14 ppm wet weight, even in ot ters in good condition in thriving populations. Otter population densi ties were known in some of the study areas; in Shetland numbers increa sed over the study period, and the density was relatively high also el sewhere in Scotland. There was a strong negative correlation between P CB and body condition, but no correlation between PCB concentration an d age of otters (mean age=4.1 years), which suggests that PCBs do not accumulate substantially in otters in the long term. The observations cast doubt on the significance of published 'critical levels' of PCBs to otter populations, based on data obtained from captive mink. Copyri ght (C) 1996 Elsevier Science Ltd.