Science & Data

This report furnished information on the sixth year of Pelagic research on fur seals conducted by the United States as specified by the Interim Convention on Conservation of North Pacific Fur Seals.

Complete protection of female seals was one of the principles followed in restoring the reduced Pribilof seal population, after signing of the Fur Seal Convention of 1911. The steady growth of the population from 1911 to about 1940 illustrated the effectiveness of this principle. After 1940 the failure of the kill of males and the number of harem bulls to increase raised doubts about the population figures in use and the wisdom of continuing current management methods indefinitely.

This report contains information on the seventh year of pelagic fur seal research by the United States under the Interim Convention on Conservation of North Pacific Fur Seals. The first of two phases of the investigation in 1964 was on the distribution, abundance, migration, and feeding habits of fur seals off California, Oregon, and Washington in April and May; the second was on the occurrence and feeding of fur seals in Bering Sea in July, August, and early September. Reproductive condition of females was also studied.

Two recent advances in research are important for the management of fur seals (Callorhinus ursinus ) on the Pribilof Islands. First, we are making better estimates of the number of pups born, the number of females required to bear these pups, and the number of females needed each year to replace those that die. Second, we are studying the value of finished sealskins by age and sex.

Annually the Bureau of Commercial Fisheries reports on its fur seal investigations on the Pribilof Islands and at sea. Investigations on the islands are directed mainly toward the development of a rational system for holding the seal population at the level of maximum productivity. At sea, the primary motivations for research are the problems of fur seal predation on commercially important fish and the intermingling of seals from the eastern and western Pacific Ocean. It is unlikely that unequivocal conclusions can be reached soon on either problem. General understanding of the pelagic life of fur seals, however, has been greatly improved during the past 9 years of research.

The problems of managing international resources have collectively been the strongest influence in establishing and maintaining a sustained research program for the northern fur seal. Investigations intended to supply information needed by the North Pacific Fur Seal Commission for management of fur seals have continued since 1956 on the Pribilof Islands and since 1958 at sea.

The year 1968 marks an important step in studies of the Pribilof Islands fur seal population. Now, 13 years after we first began to reduce the seal population with the expectation that a smaller population would yield larger kills and more stability, we are ready to let it increase in size. The high population of the 1950s has been reduced and held at nearly the same level since 1963. An estimate of the mean kill of males from the year classes at this lower population level and the size of fluctuations to be expected in the kill will be determined from collections of data completed by 1972.

In 1969 the Pribilof Islands fur seal population began its climb to a new level. Females will not again be killed intentionally until about 450,000 pups are born annually. We are not able to predict how many years will be required for this level of pup production to be reached. With average survival, perhaps 5 years will be needed to accumulate a total of more than 700,000 females 3 years old or older needed to produce 450,000 young. Exceptional survival such as that experienced by the year classes of 1952 and 1958 or poor survival like that of the year class of 1956 will substantially change the time required to bring the number of females to the desired level.

The primary objective of conducting fur seal research on the Pribilof Islands is to determine the level at which the herd will produce a maximum sustained yield. The investigations satisfy obligations to the "Interim Convention for Protection of North Pacific Fur Seals" and produce the information needed to manage the resource. This report summarizes the data collected in 1970.

The objective of fur seal research on the Pribilof Islands is to determine the level at which the herd will produce maximum sustained yield. The investigations satisfy obligations to the "Interim Convention for Protection of North Pacific Fur Seals" and produce the information needed to manage the resource. This report summarizes the data collected in 1971.