Science & Data

Alaska Fur Seal Investigations in the Pribilof Islands.

The goal of fur seal management became clearly apparent during the development and final casting of ideas at the North Pacific Fur Seal Conference in 1955-56. The prime objective of management is to attain maximum sustained productivity. The research will be designed to indicate the kind of management practices which will result in achieving the prime objective. Directing of research toward this end will not restrict it to a narrow unimaginative channel because most biological facts about fur seals are useful and necessary for intelligent management. A large part of the effort will. however, be expanded upon those aspects which are indispensable for an understanding of the current composition and condition of the Pribilof seal herd.

The goal of fur seal research and management is not a changing target. Therefore, the objectives are essentially those stated previously. Some aspects are more clearly defined but the primary objective of fur leal management is still to attain maximum sustained productivity. The research will continue to be designed to indicate the steps necessary to ~chieve the primary objective and to recognize what progress is being made toward it. Population, reproduction, and mortality studies receive principal emphasis because the problem is largely an ecological one. The investigators are attempting to understand the reaction of the fur leal herd to various environmental factors including harvest by man.

Continued use of the same objectives as the goal for fur seal research and management does not reflect a lack of originality. Much effort is continuously being put into developing new ideas and techniques which will enable researchers to effectively guide the steps required to achieve maximum sustained productivity. Population, reproduction, and mortality studies receive principal emphasis because the problem of fur seal research is largely ecological. In addition to the efforts made to understand the reaction of the fur seal herd to basic environmental factors, research must consider the commercial and economic aspect of the sealing operation.

In 1958, the first pelagic research was carried out lUlder the terms of the Interim Convention on Conservation of North Pacific Fur Seals which is scheduled to last for six years.

Reaching the objective of fur-seal research and management, maximum sustained productivity from the Pribilof, seal herd, is now complicated by acute fluctuations in the size of year classes. When the experimental approach to the calculated point of maximum yield began in 1956, year-class fluctuations were moderate, as they apparently had been since commercial sealing resumed after the Convention of 1911. These sharp fluctuations stimulated renewed emphasis on ways to forecast year-class success and, consequently, the probable size of the kill. Island seal-pup mortality, number of 2-year-old seals taken, and early season kins. of 3-year-old seals have shown some promise as indicators for making kill-size predictions. Measurements of condition or growth may be supplementary information indicative of the relative success of a year class. Recent studies suggest an inverse relationship between the return of bachelors and year-class size.

The second year of pelagic fur seal research was carried out in 1959, under the terms of the Interim Convention on Conservation of North Pacific Fur Seals.

The United States began an experiment designed to obtain maximum sustainable productivity of the fur-seal resources concurrently with the drafting of the Interim Convention on Conservation of North Pacific Fur Seals.

The third year of pelagic fur seal research, under the terms of Interim Convention on Conservation of North Pacific Fur Seals, was carried out in 1960 off Alaska. Two vessels, chartered by the United States for the research, worked from March to May from near Sitka into the Gulf of Alaska, in June between Kodiak and Unalaska, and in July and August from Unimak Pass to Pribilof and St. Matthews Islands, and adjacent sea area. Only one vessel operated during March and the first half of April and during July and August.

The Pribilof fur seal herd has twice demonstrated its resilience by recovering from excessive exploitation. About 40 years were required, in its most recent recovery, for the herd to increase from about 200, 000 to a near peak population estimated at 1,500, 000. Relatively simple management consisting of protecting females and killing a selected group of males on land was sufficient to permit herd recovery. The steady increase in the number of skins harvested, until about 1940, satisfied responsible officials that management, and consequently research, was adequate.