CHLORINATED-HYDROCARBON CONTAMINANTS AND PRODUCTIVITY OF BALD EAGLE POPULATIONS ON THE PACIFIC COAST OF CANADA

From 1991 to 1995, we studied bald eagle populations breeding near thr ee pulp mills in the Strait of Georgia, in the Fraser River estuary, a nd at remote reference sites on the west coast of Vancouver Island, no rthern Johnstone Strait, and the Queen Charlotte Islands (Haida Gwaii) . Our objective was to determine occupancy of breeding territories, me asure nest success, and compare the results to chlorinated hydrocarbon levels in eggs and in nestling plasma samples. Blood samples were col lected in 1993 and 1994 from 52, nestlings in 38 nests and plasma anal yzed for polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCD Fs), biphenyls (PCBs), organochlorine (OC), pesticides, and lipid cont ent. Most measured compounds partitioned with plasma lipids. with the exception of hepta-and octachlorinated dioxins and furans. Because of significant variation in plasma lipid content among sites, contaminant concentrations were adjusted using analysis of covariance (ANCOVA). M ean concentrations of 2,3,7,8-substituted PCDDs, PCDFs, and calculated international toxic equivalents (1-TEQs) in nestling plasma were high est in samples from near pulp mills on southeast Vancouver Island (Nan aimo and Crofton) and Powell River. Mean total PCB concentrations were also highest in the industrialized Strait of Georgia region, such as at Powell River (56 mu g/kg). while OC pesticide concentrations, inclu ding 1,1-dichloroethylene bis(p-chlorophenyl) (DDE), did not vary sign ificantly among sites. Nest success was followed for 5 years at 250 br eeding territories in the nine study areas. Average productivity was h igher at most study sites around the Strait of Georgia compared to the reference areas. There were no significant relationships between prod uctivity and I-TEQs or any tetrachlorodibenzo-p-dioxin-like compounds for the whole data set; only DDE in plasma was weakly related to produ ctivity. Likewise, there were no significant relationships between ind ividual nest productivity and contaminant levels in eggs, based on pre viously published data. We also rested for variability within study ar eas by comparing productivity at nests adjacent to dioxin fishery clos ure areas at three pulp mills compared to nearby nests outside the clo sure areas. At two pulp mill sites, Powell River and Nanaimo, there we re no differences in productivity; however, at Crofton, average produc tivity, 0.26 young/occupied territory, was significantly lower at nine bald eagle territories adjacent to a dioxin-fishery closure zone comp ared to eight territories outside of the closure area, 1.0 young/occup ied territory. The cause of the low reproductive rate at Crofton has n ot been determined, although a toxicological explanation has not been ruled out.