Fraser River Sockeye Fisheries and Fisheries Management - Cohen ...

maintaining genetic diversity in captive Cultus sockeye populations, and increasing thenumber of sockeye recruits (hatchery fish). Nevertheless, the CSRT ConservationStrategy objectives (listed above) have not been met. With regard to Objective 1, themean number of successful spawners for the most recent four years (2006-2009) was1,426 compared to the goal of 1,000; however, in 2008 the escapement estimate was 340compared to the minimum target level of 500 in any year. Objective 2 calls for observedincrease in escapement for at least three of four consecutive years; however, escapementsin 2008 and 2009 were lower than those observed four years earlier in 2004 and 2005.Cultus sockeye have not recovered to a level of abundance sufficient for COSEWIC toconsider de-listing this population (Objective 3) and therefore this stock is a long wayfrom achieving Objective 4. Given the uncertainty associated with the outcomes ofvarious conservation actions, ongoing efforts should be considered “experimental” andthus require ongoing and rigorous monitoring programs. Key knowledge gaps areidentified.Cultus Lake Sockeye Conservation StatusEscapement for the Cultus Lake sockeye stock has been monitored since 1921 (Figure23). Beyond the large fluctuations in the size of the dominant run cycle, which peaked inthe 1920s and late 1930s, there has been a precipitous decline in the size of the Cultusstock since the 1970s. Causes of the population decline include: (i) overexploitation, (ii)early migration into Cultus Lake causing increased exposure to parasitic disease and highpre-spawn mortality, (iii) invasive species such as the aquatic plant Eurasian watermilfoilthat destroys salmon habitat and improves salmon-predator habitat, (iv) in-lake predationon juveniles by Northern Pikeminnow, and (v) Cultus Lake habitat alteration anddestruction (COSEWIC 2003). Early evidence suggests the population decline may havestopped over the past two cycle years (DFO 2010).118