Science Advisory Report 2008/058

Science advice on harvesting of northwest Atlantic Harp seals (Pagophilus groenlandicus) in 2009

Summary

• Northwest Atlantic harp seals are harvested in Canadian and Greenland waters. After averaging approximately 52,000 seals per year between 1983 and-1995, reported Canadian catches increased significantly to a range of 240,000 to 366,000 between 1996 and 2006. Catches were significantly reduced in 2007 (224,745) and 2008 due to lower quotas and poor ice conditions.  Greenland catches have increased steadily since the mid 1970’s reaching a peak of approximately 100,000 in 2000. They subsequently declined to approximately 70,000 but have since increased to 90,000 in the most recent years for which we have data (2005-06). Catches in the Canadian Arctic remain low (<1,000).
• Total removals of harp seals was estimated by including reported catches, estimates of bycatch in the Newfoundland lumpfish fishery and estimates of seals killed, but not recovered during harvesting in the different regions. From 1996 to 2004, high catches in Canada and Greenland resulted in average annual removals of 465,500. However total removals in 2008 was estimated to have declined to slightly over 400,000, primarily due to the lower catches in Canada.
• Using aerial surveys, the total pup production of harp seals in 2004 was estimated to be approximately 991,400 pups (95% confidence interval 877,300 to 1,105,500). This estimate is similar to the previous estimate obtained in 1999. A survey was carried out in 2008 but the results will not be available until 2009.
• The harp seal population declined during the 1960's and reached a minimum of less than 2 million in the early 1970's. Since then it increased steadily until the mid 1990's when it reached the highest level estimated. Due to the large harvests over the past decade, the population has been relatively stable since 1996.
• The estimated population size of northwest Atlantic harp seals for 2009 is 5.6 million (95% CI=3.9-7.2 million) animals. The most recent estimates for maximum population in 2005 is 5.7 million (95% CI= 4.4-6.9 million) which is slightly lower than the previous estimate of 5.8 million (95% CI= 4.1-7.6 million). This difference is small compared to the uncertainty in these estimates.
• Demographic momentum associated with the high harvests recorded over the last 12 years is having a major impact on the current population and pup production.
• A harvest of 270,000 animals would respect the plan in 2009, but may require substantial reductions in the TAC for the 2010 season. Harvest scenarios with catches of 300,000 animals would not respect the management objectives and would result in the projected population dropping below N70 in 2009.
• This assessment relies on pup surveys completed once every five years combined with estimates of reproductive rates and removals to determine total abundance using a population model. The variability associated with model parameters, as well as potential changes in natural mortality rates due to environmental conditions add uncertainty to these estimates. Additional uncertainty is associated with the use of pup surveys to assess abundance. Because surveys are only completed once every five years and only count pups, changes in natural mortality rates in intervening years may not be detected until 10-15 years later during subsequent assessments.

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