MARINE MAMMAL COMMISSION — Annual Report for 1992 
they occur nearly continuously along the Pacific Rim, 
from San Ignacio Lagoon, Baja California, Mexico, 
north through southeastern Alaska, and west to the 
Bering Sea, the Aleutian, Commander, and Kuril 
Islands, and south to Hokkaido, Japan. 
In the early 1970s approximately 270,000 harbor 
seals were estimated to occur in the coastal waters of 
Alaska. Although there is no current statewide 
estimate, counts made since the early 1970s at certain 
harbor seal rookeries and haulout sites in the Gulf of 
Alaska and Bering Sea indicate significant declines in 
some areas. In 1988 the Commission published a 
review of current information on the biology, ecology, 
and status of harbor seals in Alaska as part of a report 
on a number of Alaska marine mammals (see Appen- 
dix B, Lentfer 1988). This species account indicated 
a dramatic decline in the number of harbor seals in 
parts of Alaska. 
To help document population trends, in 1990 the 
Commission provided funds to the Alaska Department 
of Fish and Game to count harbor seals on Tugidak 
Island in the central Gulf of Alaska. Tugidak was 
believed to have the largest concentration of harbor 
seals in the world as recently as the mid-1960s when 
up to 20,000 seals hauled out on the island. By the 
mid-1970s, however, the average count had declined 
to fewer than 7,000 seals. The 1990 survey found 
fewer than 1,000 animals, a decrease of 86 percent 
since the mid-1970s. Additional anecdotal informa- 
tion collected by the National Marine Fisheries 
Service suggests that these numbers may be indicative 
of harbor seal population trends throughout the 
Kodiak Archipelago. 
The reason for the decline is unknown. Mass 
mortalities of harbor seals due to disease have been 
observed in recent years at locations outside Alaska. 
In 1979-1980, 450 harbor seals along the New Eng- 
land coast succumbed to an influenza virus, and in 
1988 phocine distemper killed approximately 17,000 
harbor seals in the North Sea and Baltic Sea. Other 
maladies have afflicted harbor seals to lesser degrees 
both within and outside of Alaska, including herpes 
virus, Leptospira spp., Chlamydia psittaci, San 
Miguel sea lion virus, Tillamook (bovine) calicivirus, 
and seal pox. Of these, only the San Miguel sea lion 
virus and seal pox have been reported in harbor seals 
in Alaska, and the effects have been either minor or 
undetermined. Further, there have been no reports of 
diseased animals at Tugidak Island, where the decline 
in harbor seal numbers has been most prominent. 
Commercial and bounty hunting no doubt affected 
harbor seal numbers in Alaska prior to passage of the 
Marine Mammal Protection Act in 1972. Since 1889 
or earlier, harbor seals were taken commercially for 
their pelts and meat and, at various times, under a 
bounty program to reduce perceived conflicts with 
fisheries. Harvests increased from 6,000-10,000 
animals in the 1930s and 1940s to 40,000-60,000 
animals in 1964-1966 when commercial demand for 
seal skins was at its peak. The harvest size decreased 
significantly beginning in 1967, reaching a low of 
between 8,000 and 12,000 animals in 1972 when the 
harvest was banned with the passage of the Marine 
Mammal Protection Act. The fact that numbers have 
decreased rather than increased since the mid-1970s 
suggests that commercial and bounty hunting are not 
the cause of the decline. 
Harbor seals also are taken for subsistence purpos- 
es by Alaska Natives. Although data on the annual 
subsistence take of harbor seals are sketchy, some 
estimates indicate that as many as 2,000-3,000 animals 
may be taken each year. Beginning in 1992 the 
National Marine Fisheries Service initiated statewide 
monitoring surveys of Native subsistence use of 
marine mammals in Alaska. Over time, this moni- 
toring should accurately identify levels of subsistence 
use of harbor seals and potential effects of that use on 
seal numbers in different parts of Alaska. 
A number of other activities may be affecting 
harbor seals in Alaska, including reduction of prey 
species by commercial fisheries and the incidental take 
of seals in fishing gear. Disturbance by boat and 
aircraft traffic and activities related to offshore oil and 
gas exploration, and the release of contaminants such 
as polychlorinated biphenyls (PCBs) and heavy metals 
into the environment also may affect the seal popula- 
tions. The similarity between the harbor seal and 
Steller sea lion declines in Alaska, and the fact that 
the Steller sea lion decline may be related to nutrition- 
al factors, suggest that the harbor seal decline may 
also be food-related. 
