IMPACT OF ORGANOCHLORINE PESTICIDE-RESIDUES AND PCBS ON OTTERS (LUTRA-LUTRA) - A STUDY FROM WESTERN BRITAIN

A study of otter (Lutra lutra) populations and levels of organochlorin e (OC) pesticide residues and PCBs in otter droppings (spraints) was m ade on eight stretches of river in three catchments in Wales and West Midland England. Population and Contaminant levels were compared again st target values. The otter populations (as measured by an index) rema ined stable on one stretch over 11 years, while they increased rapidly to equilibrium on four other stretches. The three lower stretches of rivers showed more erratic trends and on only one stretch did the inde x exceed, occasionally, the target value. Marking intensity at spraint sites was also lower at the three lowland sites. Concentrations of di eldrin, DDE and PCBs were significantly greater in spraint samples fro m the three lowland stretches. Over 50% of samples from the three lowl and stretches had OC concentrations above the maximum allowable concen tration, whereas most samples from the upland stretches had concentrat ions below the 'no effects level'. It is suggested that the colonizati on, by otters, of their former lowland range is inhibited by OC contam ination of their food chain but, if contaminant levels can be reduced, spread will occur rapidly.