To assess the survival rates of killer whales in lean years, the study examined census data for two populations, of Washington State and British Columbia, as well as annual catch numbers from chinook salmon fisheries in the Pacific Northwest.

为了评估虎鲸在淡季的存活率，该研究调查了美国华盛顿州和加拿大不列颠哥伦比亚省沿岸两个虎鲸种群的统计数据，以及太平洋西北部奇努克鲑鱼渔场的年度捕获量。