Chilko Tales

Acoustic Tagging Chilko Sockeye

Acoustic Tagging of Chilko Sockeye Salmon Smolt

Technology brings wonderful advances to science and one of the greatest new gadgets is Acoustic Transmitters (or tags). What makes them so great?  It allows scientist to track our fish and identify migration patterns.  It allows us to learn about our wild fish, how they travel, where they go, and more importantly what we can change in our own environment so we don’t get in the way of theirs.   

In 2010 a project was started on the Chilko River Sockeye by researchers from UBC and Kintama Research Ltd.  They started by surgically inserting acoustic transmitters in 200 little bellies of Chilko Sockeye Smolt.  They kept the sockeye smolt in a holding pen for 24 hours and released them back into the river to continue their journey to the Pacific Ocean.  Acoustic receivers were placed at a variety of locations along the Chilko River, Fraser River, and even on the tip of Vancouver Island.  As the small smolts swim by the receivers it picks up the acoustic transmitter signal and tracks them on their journey.  Acoustic transmitters differ from radio transmitters; they use sound waves instead of radio waves to determine the location of the fish.  

The results of the project in 2010 raised more questions than it answered and were a bit surprising.  Almost 80% of the tagged sockeye did not survive their swim to the mouth of the Fraser River. What was most surprising was that 50 % of them did not make it past Henry’s.  The big question becomes why?

Nature does weed out the weak, but this seems to be a bit extreme. The obvious questions are:   Does the surgery itself cause an increase in mortality of the smolt?  Normally the mortality rate is about 1 %? Did the surgery cause an infection? Do the tags cause the smolt to be more susceptible to predators because it slows them down?  After the smolts start their migration to the Pacific Ocean, is the river a bit of a shock especially the lower river at Lava Canyon, a canyon where the river is condensed into a 30 foot wide canyon and there are major rapids –  a river rafter’s dream trip but a smolts biggest boogey man?  Is Bud’s theory that the mergansers eat all the smolt true?  Questions and more questions!  So in order to rule out as many questions as possible, in the spring of 2011 they replicated the 2010 system and tagged more – another 650 sockeye smolts and once again released them into the river.  At this point I am aware of the results but I have been asked to not post them until the entire analysis is done.  Although I would really like to, I will respect their wishes and wait for the official report… oh hum…

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