Research Document - 2005/050

Estimates of human induced mortality in Northwest Atlantic Harp Seals, 1952-2004

By Stenson, G. B.

Abstract

The Northwest Atlantic harp seal (Pagophilus groenlandicus) population is subjected to various types of human induced mortality including subsistence harvests in Greenland and the Canadian Arctic, commercial catches in southern Canadian waters, animals that are killed but not landed (’struck and lost’), and bycatch in commercial fishing gear. Information on catch levels and age structure of removals are necessary for accurate population estimation and responsible management. The objective of this report is to summarized available estimates and update them for the years 1952 - 2004. Commercial and subsistence hunts account for the majority of the removals. Between 1952 and 1971, catches taken in the Canadian commercial hunt averaged in excess of 288,000 seals. Between the introduction of quotas in 1972 and the demise of the large vessel hunt in 1982, an average of 165,000 seals was taken annually. Catches decreased after 1982 and remained low, averaging approximately 52,000, until 1995. Annual catches, consisting primarily of young of the year, increased to an average of 258,000 between 1996 and 2004. The age composition of catches at the Front and in the Gulf were estimated based on reported numbers of pups taken and biological sampling of seals one year of age and older (1+) taken from the commercial harvest and research samples. Prior to 1980, catches in Greenland were consistently less than 20,000 animals. Since 1980 Greenland catches increased relatively steadily to a peak of over 100,000 in 2000. In recent years, catches have declined to just under 70,000. Estimates of the age composition of seals harvested in Greenland were obtained from biological samples collected in West Greenland between 1970 and 1993. Although limited data are available on catches in the Canadian Arctic, they appear to be relatively low (generally <5,000). A recent study indicates that current catches average less than 1,000 per year. Estimates of harp seal bycatch in the Newfoundland lumpfish fishery increased from less than 1,000 in the early 1970s to 46,400 in 1994. By 2003, they had declined to approximately 5,000. Low numbers of harp seals (<1,000) are also caught in US fisheries. The average total removals from 1952 – 1982 was approximately 388,000, but declined to 178,000 per year between 1983 and 1995. Since 1996, higher catches in Canada and Greenland resulted in average annual removals of 471,000. Young of the year account for approximately 68% of the current removals. Due to the limited data available on age structure of older (1+) seals, it may be more appropriate to assume that 1+ age classes are proportion to abundance when using these data to model population dynamics. Appropriate methods of incorporating uncertainty into these estimates of total removals and age structure should be developed.

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