river runs, and the most famous is the Fraser River sockeye run. The Fraser River salmon run has experienced declines in productivity since the 1990s, mirroring a similar decline in the 1960s. The return abundance (population) of Fraser River sockeye in 2009 was estimated at a very low 1,370,000, 13% of the pre-season forecast of 10,488,000. That represented a decline from the recent (1993) historical cycle peak of 23,631,000 and the return abundance was the lowest in over 50 years. The reasons for this (former) decline remain speculative. According to a consortium of scientists assembled to review the problem, the decline highlights the uncertainty in forecasting salmon returns. After the low returns, the Government of Canada launched a formal inquiry into the decline, the Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River. The Commission has been tasked with investigating all the factors which may affect Fraser River sockeye salmon throughout their life cycle. According to the terms of reference, the subjects of investigation are "the impact of environmental changes along the Fraser River, marine environmental conditions, aquaculture, predators, diseases, water temperature and other factors that may have affected the ability of sockeye salmon to reach traditional spawning grounds or reach the ocean." During the commission, hundreds of thousands of documents and scientific research papers were reviewed. Twelve technical reports were published using that information, looking at the possible impacts of diseases and parasites, hatchery diseases, contaminants, marine ecology, salmon farms, fisheries, predators, climate change and government management on the productivity of Fraser River sockeye runs. While the commission was holding public hearings, in the late summer of 2010, the largest run of sockeye since 1913 returned to the Fraser River system. Final counts show that approximately 30 million salmon returned to the Fraser River and its tributaries in 2010. In total, approximately 11,591,000 Fraser sockeye were caught by Canadian fishers and 1,974,000 Fraser sockeye were caught by American fishers. The final projected escapement (fish which were not caught) was 15,852,990 fish. Recent unpredictable fluctuations in runs are speculated to be due to changing water temperatures. There is high variation in thermal tolerance among the different sockeye salmon populations that migrate up the Fraser River. The Chilko River sockeye salmon population is able to maintain cardiorespiratory function at higher temperatures, which may make them more resilient to the effects of rising river temperatures. In one study