A. Critical Study of Pribilof Fur Seal Population Estimates

Previously unresolved problems in the populations studies of the Pribilof fur seal are reviewed. The tagging estimates of fur seal pups may have been biased by tag mortality and hence the apparent year class fluctuations after 1952 may be unreal. A set of cumulative estimates are given for the number of pups born in each year since 1950. These cumulative estimates depend on the estimate of the ratio of survival of Nagasaki (1961) and Chapman (1960 have published models of the population dynamics of the Pribilof fur seal which, while based on different hypotheses, lead to .very similar eonclusions. These have been summarized in a report of the North Paeific Fur Seal Commission (PFSC). 2 Both models are based upon estimates of the pup population from tag recoveries. Such studies of population dynamics are basic to a proper management of the fur seal herds, both to maximize yield and to evaluate the effect of the herd on other living resources of the sea. Moreover the applieation of methods to this population which has been extensively studied and for whieh mueh data are available, are useful; such applieations show up the strength and weakness of theoretical procedures and pave the way for a more intelligent application to other valuable marine resourc.es for which studie,s are in mueh earlier stages. NOTE.-ApproVl'd for publleatlon'May 7, 1964. I Research supported In p.~rt by National Science Fowldatlon Grant No. 0-19645. 2 North Pacific Fur Seal Commission, 1962. North Pacific Fur Seal Commission Report on Investigations from 1958 to 1961. Manuscript report, Washington, D.C. Frequent reference will be made to this report, hereafter called FSCR. FISHERY BULLETIN: VOLUME 63, NO.3 (1964) females to males from birth to age 3. An estimate of this ratio is given. The implications of this study on the population dynamics model of the fur seal are reviewed: in particular while the exact model is less definite, the suggested optimum population level is almost unchanged from that sugl1ested in earlier