FISHERY BULLETIN: VOL. 78, NO. 4 



history of the fishery and of the population since 

 the early 1900's. For example, we do not know how 

 the 1912 population was structured. If, as seems 

 likely with high prices for baleen, selection mainly 

 for large animals with long baleen occurred near 

 the end of the fishery, then the remnant population 

 might have comprised a large proportion of young 

 animals. The 1977 population might represent a 

 considerable proportion of this 1912 population, 

 now old, and we would know little about net re- 

 cruitment or failure thereof. 



The most difficult parameter to estimate in any 

 whale population is the recruitment rate. In the 

 absence of better knowledge, we have used a sim- 

 ple linear model and specified a range of maximum 

 net recruitment rates. Given that the recruitment 

 rate function varies between some maximum 

 value at stock level near zero and M at Pq, the 

 shape of the curve has less effect than the value of 

 (r- M)j^3^. During the early history of the fishery, 

 catches exceeded recruitment, and during the last 

 half-century the stock was at a relatively low 

 level. Thus, the recruitment rate was close to its 

 maximum and varied little. A further study could 

 consider the effect of a dome-shaped recruitment 

 curve. 



Given our results, it appears likely that stock 

 size between 1910 and 1978 was probably <10% of 

 the initial stock level. According to most classical 

 models used with baleen whale populations, the 

 net recruitment should have been near its 

 maximum for about the last 60 yr. Because the 

 population does not appear to have grown substan- 

 tially since then, either the recruitment rate has 

 been low or the kills have been higher than cur- 

 rently estimated. It is also possible that the 

 catches during the last half-century represent 

 survivors of the then young animals. 



Aspects of the Fishery 



We may have to consider very low net recruit- 

 ment rates because the changing nature of the 

 fishery suggests that, as the worst case, the whalers 

 efficiently decimated a structured population suc- 

 cessively over its geographic range. The argument 

 is as follows: females with calves migrate farther 

 north (later, in the migration stream) and also 

 inhabit ice fields. They might not have been as 

 available to the early fishery, 1850-ca. 1870's, 

 which used sailing vessels at the ice edge and 

 which was mainly a midsummer to late season 

 fishery. The greatest removals were during this 



time and for a short period. Subsequently, with the 

 development of steam whaling, overwintering of 

 the fleet became possible, and heavy fishing oc- 

 curred in the ice fields at all times. The fishing 

 season was effectively increased in length between 

 the 1880's and 1910's. (Even if the population were 

 not so structured by sex or age, the present spring 

 and summer distribution is confined to a much 

 smaller area compared with the data of Townsend 

 (1935).) 



Due to the unique geography, stratification, and 

 timing of this fishery, the possibility exists that 

 once the stock is fished to some low level, recruit- 

 ment failure could occur and that net recruitment 

 since about 1900 could indeed be as low as 0.01, the 

 minimum figure used in our calculations. 



Any subsequent analysis of annual catch and 

 effort data (e.g., including number of vessels, etc.) 

 should consider changing technology. The fishery 

 changed radically from one of a sailing vessel-ice 

 edge-early season fishery to a steam vessel-ice 

 pack-nearly year round fishery. The best measure 

 of change in effort between sailing and steam ves- 

 sels to catch the same number of whales might be 

 the monthly duration of the respective voyages. 



ACKNOWLEDGMENTS 



We thank M. F. Tillman, D. W Rice, and V M. 

 Kozicki for critically reading the manuscript. G. 

 Ferrand drafted Figure 1. J. M. Breiwick acknowl- 

 edges support under contract MM8AC007 from 

 the U.S. Marine Mammal Commission. 



LITERATURE CITED 



Allen, K. R. 



1966. Some methods for estimating exploited popula- 

 tions. J. Fish. Res. Board Can. 23:1553-1574. 

 BRAHAM, H., B. KROGMAN, S. LEATHERWOOD, W Marqliette, 



D. RuGH, M. Tillman, J. Johnson, and G. Carroll. 



1979. Preliminary report of the 1978 spring bowhead 

 whale research program results. Rep. Int. Whaling 

 Comm. 29:291-306. 



Clark, A. H. 



1887. Part XV The whale fishery. 1. — History and present 

 condition of the fishery. In G. B. Goode and a staff of 

 associates, The fisheries and fishery industries of the 

 United States, Sect. V Vol. 2, p. 3-218. Gov. Print. Off, 

 Wash., D.C. 



Cook, J. A. 



1926. Pursuing the whale. A quarter-century of whaling in 

 the Arctic. Houghton Mifflin Co., Boston, 344 p. 



Cox, D. R., AND H. D. Miller. 



1965. The theory of stochastic processes. Wiley, N.Y, 

 398 p. 



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