. The Canadian field-naturalist. Natural history. 1997 Baird and Hanson: Status of Northern Fur Seal 267 =*=*.=i=t 1 â 11111111111=^. MIGRATORY ROUTES AND BREEDING AREAS OF NORTHERN FUR SEALS Migration route Primary distributK 120 OOE 130 00 140 00 150 00 160 00 }70 00 180 OOW 170 00 150 00 140 00 130 00 120 00 Figure 2. Distribution of the Northern Fur Seal off the west coast of North America. Breeding islands are located in the circles. Reproduced from Loughlin and Miller (1989) by permission. population may be enhanced by increased sea sur- face temperatures associated with these events (Yo
. The Canadian field-naturalist. Natural history. 1997 Baird and Hanson: Status of Northern Fur Seal 267 =*=*.=i=t 1 â 11111111111=^. MIGRATORY ROUTES AND BREEDING AREAS OF NORTHERN FUR SEALS Migration route Primary distributK 120 OOE 130 00 140 00 150 00 160 00 }70 00 180 OOW 170 00 150 00 140 00 130 00 120 00 Figure 2. Distribution of the Northern Fur Seal off the west coast of North America. Breeding islands are located in the circles. Reproduced from Loughlin and Miller (1989) by permission. population may be enhanced by increased sea sur- face temperatures associated with these events (York 1991). The 1983 El Nino occurred just prior to implantation of embryos at San Miguel Island, and resulted in an increase in pup mortality and a decrease in pup weights. DeLong et al. (1993) sug- gested that the later onset of the 1992 El Niiio affect- ed this population less intensely. Competition with fisheries has been suggested as a possible limiting factor for this species, both in waters surrounding breeding colonies, along migration routes, and dur- ing the non-breeding season in the North Pacific. The interactions between commercial harvesting of prey species and fur seal movements, reproductive rates or mortality is unclear, however (National Marine Fisheries Service 1993). Calambokidis and Peard (1982) examined levels of chlorinated hydrocarbons from Northern Fur Seals in Alaska, but found concentrations well below lev- els thought to contribute to reproductive problems in other populations of pinnipeds. Anas (1974) reported levels of heavy metals in fur seals from Alaska and Washington State, but no information is available on potential impacts. An analysis of heavy metals by Noda et al. (1995) revealed higher cadmium concen- trations in northern fur seals than in other otariids. Cadmium levels were higher, and mercury levels lower, than those reported by Anas (1974); however, heavy metal concentrations in Northern Fur Seals are variable with age, location, and pr
Size: 2054px × 1217px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectnaturalhistory, booky
