One of the most fascinating characteristics of pacific salmon is their ability to travel thousands of kilometres, from feeding grounds in the ocean, back to the streams and rivers where they were born.
At an early age, juvenile salmon learn or imprint on odours associated with their natal stream, and later, as adults, these same attributes call them back to their birth place.
This homing behaviour is the focus of a new multi-year study being conducted by Project Watershed in collaboration with Fisheries and Oceans Canada, Puntledge River Hatchery.
The study is being funded by BC Hydro’s Fish and Wildlife Compensation Program (FWCP) to address concerns related to recovery of the Puntledge River summer chinook salmon stock, which is a genetically unique salmon population, considered to be at risk.
The study objective is to determine if a group of summer chinook salmon, which has imprinted in Comox Lake as juveniles, has greater success in reaching the lake as adults, compared to a “control” group which has been released directly to the river from the hatchery.
Results from past research on the river have clearly demonstrated that early returning adult summer chinook salmon (those arriving before July) have the greatest success in reaching Comox Lake. By arriving early, these salmon can easily navigate Stotan and Nib falls during freshets and hold in the depths of Comox Lake, where the water is colder.
Because these fish aren’t subjected to the stresses of summer water temperatures, predators, and low flows found in the river, they survive to spawn with double the success, compared to later arrivals, which stay in the river.
In the homing behaviour study, 90,000 salmon fry that were reared at Puntledge Hatchery were released into Comox Lake in May 2011, so they could imprint on the lake characteristics before migrating to the ocean. The other group was released directly into the lower Puntledge River.
These two groups of fish are returning to the river as adults, and subsets of the two groups will be marked with special electronic tags at the Puntledge Hatchery and released back to the river to spawn naturally. Their continued migration will be monitored using antennas setup in various locations along the river that detect each fish as they move upstream.
It will take a couple of years to obtain results, since the majority of the salmon will return as adults next year, after spending a full 3 summers in the ocean. The final results of the study will provide a scientific-based strategy for managing juvenile out-migration and adult return migration and improve efforts to maintain the viability of the summer chinook stock.
Puntledge River chinook stocks are important to a number of First Nation communities, and important components of the current Georgia Basin recreational and commercial fisheries.
The summer and fall runs originated from the same salmon population historically. Over thousands of years, the Puntledge summer chinook evolved to become genetically distinct from the fall chinook, and unique among chinook stocks in the Georgia Basin.
It is the genetic distinctiveness of the summer-run stock that has ranked them as an important stock for Fisheries and Oceans Canada’s (DFO’s) salmon enhancement efforts.
In 1999 the Fish and Wildlife Compensation Program (FWCP): Coastal Region was created to offset the impacts resulting from construction of BC Hydro dams. Ever since, it has continued to offer grants which support recovery efforts for fish and wildlife and it is sponsored through a partnership among BC Hydro, DFO and the Provincial Ministry of Environment.
— Esther Guimond, RPBio