The past 20 years has seen the extraordinary decline of marine survival of salmon and the loss of most of the commercial salmon fishery in British Columbia, and along with it close to 20,000 jobs. The extremely low abundance of returning adult Cultus Lake sockeye led to the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) upgrading the status of this population to “Endangered” in October 2002. Other stocks have declined over the same period although until recently not as precipitously. 2009 saw the worst Fraser River sockeye return in recorded history, followed by one of the best in 2010 – yet we are no closer to understanding why. Kintama has been involved in studying both Cultus Lake and Chilko Lake populations. Survival of Cultus Lake sockeye smolts during their 2004-2007 outmigration. Survival was measured by tagging hatchery smolts and then using our prototype acoustic telemetry array. In addition to estimating survival, this system allows direct measurement of speed and direction of the tagged smolts to be made.
Of particular interest is that the 2007 outmigration group was the same group for which the fishery collapsed in 2009, and yet there was no measured difference in river or early ocean survival (to the tip of Vancouver Island) between 2007 and other years.
The 2007 smolts were implanted with specially programmed acoustic tags. The programming provided for two periods of tracking: (1) covering the early period of smolt outmigration and (2) a second period of active transmission two years later when the fish were expected to return. Two of these tagged smolts (of 200 tagged smolts released; a 1% survival rate) returned in August 2009 as adults with both returning adults previously detected as smolts migrating north out of the Strait of Georgia/Discovery Passage/Broughton Archipelago (Queen Charlotte Strait) in 2007 (see Visualization). Despite their exit as smolts via Queen Charlotte Strait, the two adults both returned via the west coast of Vancouver Island, passing through the Juan de Fuca Strait within 1 day of each other in 2009 before moving back into Fraser River. The timing of river entry indicates that they did not delay in the Strait of Georgia for six weeks as was once the typical behaviour of late run Fraser River sockeye stocks, and instead exhibited the “early entry” behavior that has caused great problems for Fraser River fisheries management in recent years.
Our findings allow a partitioning of overall mortality into the first month of life in the ocean and that occurring afterwards, and are of particular importance because they demonstrate that the majority of the mortality occurred after smolts passed through the Discovery Passage/Broughton Archipelago region.
This sparks the debate of whether the poor marine survival was caused by fish farm related issues, or if other factors such as poor ocean conditions were responsible, or if there was perhaps a combination of impacts. At this time we have no answers, but we have solutions that could bring such answers.
In 2010, Kintama collaborated with the University of British Columbia on a Pacific Salmon Foundation funded project charged with providing preliminary information about Cultus Lake salmon migration and survival. These data have still to be published. However, it appears that there are 2 regions of high mortality, one shortly after leaving Lake Chilko, and the other between the Northern Strait of Georgia and Queen Charlotte Strait.
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