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Do Salmon have a Critical Mortality Period?
Tuesday, 08 December 2015

In 2015, supporters of the Salish Sea Marine Survival Project helped launch 33 projects in the Strait of Georgia engaging 30 different partners. The projects are part of an ecosystem approach to examine all factors that could be limiting wild Coho and Chinook production in the Strait. One project examined a prevalent hypothesis in the scientific community know as the 'critical mortality period.'  The hypotheses suggests that there is a specific period in salmon's life history when a significant proportion of salmon die. If we can figure out when that period is, we can determine what the key causes are. 

P.I.T. tags were applied to fish at four distinct stages in early life. The BC Conservation Foundation applied PIT tags (Passive Integrated Transponders) to more than 10,000 juvenile Chinook in the Cowichan River over two years to compare the survival of different groups of fish and what their rate of survival is.

Reasearchers used P.I.T. (Passive Integrated Transponder) tags. P.I.T. tags can be very small (1.2 cm) and inserted in very small salmon because they don’t carry a battery. Their unique ID’s can provide information on both juvenile outmigration and returning adult salmon. To detect and decode a tag, it is charged by an antenna, and the tag immediately discharges its code. Detection is possible by antennae that are hand-held or designed as mats on a river bottom. The Salish Sea Marine Survival Project will install a detection system in the Cowichan River to ensure detection of tagged Chinook and Coho returning as adult salmon.

More than 60 tagged fish have returned so far, the bulk of tagged fish are expected to return in 2016-2018.

The $10 million budget for Canadian efforts through the Salish Sea Marine Survival Project is 80% funded. But we need to continue raising $400,000 annually to keep the Project moving at full speed. To support this iniative, simply click the orange donate button at the top left-hand corner. If you donate by December 31, 2015, your donation will be doubled through our matching fund. In addition, every donation of $100 will recieve an entry to win an Artist Proof reel donated by Peet Outdoors. So $500 means five entries.