The otter (Lutra lutra) in Sweden - population trends in relation to SigmaDDT and total PCB concentrations during 1968-99

Polychlorinated biphenyl (PCB) has been suggested as the major cause of the European otter (Lutra lutra) population decline. This study investigates t emporal and geographical changes in otter numbers as well as total PCB and Sigma DDT concentrations in otters and their food in different parts of Swe den with various pollution impacts during three decades. In Sweden, rare sp ecies belong to the State and carcasses of such specimens are sent to the a uthorities. Two-hundred and eight specimens have been used to investigate t emporal and spatial variation in the otter populations during 1968 and 1999 . One-hundred and twenty-five of them have been chemically analysed. The po pulation trends in northern Sweden coincide with the temporal trends of the contaminants. When concentrations of PCBs decrease in the environment, ott er population increases. Neither aldrin/dieldrin nor mercury pollution seem to explain why the Swedish otter populations decreased dramatically during the 1960s-1980s. In southern Sweden total PCB concentrations are still hig h and the indications of improvement of the population are weak (C) 2000 El sevier Science Ltd. All rights reserved.