A five-year success rate of Uu-a-thluk and Mowachat/ Muchalaht First Nations pro- viding high quality Chinook sal- mon assessments on the Bur- man River has resulted in fund- ing for a similar program for Chinook on the Conuma River.
Led by Uu-a-thluk biolo- gist Roger Dunlop, the work is part of an international initia- tive to practice science-based conservation and sustainable harvest sharing to ensure healthy salmon stocks, and a safe return to their place of origin. Funded by the Pacific Salmon Commis- sion’s Sentinel Stocks Program, the stud- ies represent a commitment to improve the assessment of Chinook salmon along Vancouver Island’s west coast as outlined in the 2009 Pacific Salmon Treaty between Canada and the U.S.
Based on the success of work on the Burman River, the Sentinel Stocks Program provided funding to Uu-a- thluk Fisheries to initiate a similar study for Conuma River Chinook for 2014. Most of Conuma River Chi- nook salmon are produced from the Conuma River hatchery managed by Fisheries and Oceans Canada (DFO). As with the Burman River project, Uu-a- thluk partnered with Mowachat/Muchalaht First Nations to provide the Pacific Salmon Commis- sion and DFO with greatly improved estimates of the return of Chinook salmon to the Conu- ma River. The program began on September 4 and employed mark-recapture techniques using external and radio tags to estimate the number of Chinook in the Conuma River. The program wrapped up in early November and preliminary results indicate similar findings from the Burman River study; there are more Chinook returning to the Conuma River than previously thought.
“We’re seeing more fish than are being forecast,” says Dunlop. After examining the data, he discovered that the number of Chi- nook entering the Conuma River surpassed the escapement management goal by 21,000. This means the Conuma River hatchery produced almost one quarter of the WCVI enhanced Chinook in 2014.
For the study, Dunlop and his crew of six from Mowachat/ Muchalaht First Nations tagged the adult Chinook salmon with external and radio tags and then recaptured the carcasses to establish the mark rate. Comparing the number of marked to unmarked fish allows you to estimate the total number of fish.
Radio tagging allows for data to be collected on individual fish, such as when a fish dies or where and when that fish was in the river. A telemetry receiver station at the bottom of the Conuma River clocks fish coming up from the tagging area to the spawning area. Motion-sensing tags give off a dead signal once a fish stops moving. The methodologies used in the study enable Dunlop to determine— within a 20-hour period—when the fish died. Dunlop uses the data to develop early accurate estimates of the Chinook escape- ment sooner than what has been done be- fore through other methods. Escapement is defined as the number of fish that return to a river to spawn. Dunlop’s work also pro- vides estimates of the number of males and females in the river. This is important when calculating how many fish you need to let spawn.
For 2014, 75% of the returning Chinook salmon to the Conu- ma were males. “To account for this difference between the number of males and females,” Dunlop says, “you need to man- age fisheries to provide higher escapement to ensure that more females get into the river, and to make it easier for the hatchery to get their fish.” Estimates show that 9,708 females and 26,826 males have entered the stopover site of the lower river, which works out to one female for every four males.
For the past five years, Dunlop has used the mark-recapture model to assess Chinook salmon populations on the Burman, and now on the Conuma River. His findings have produced im- proved data for Chinook escapement in these rivers, and he be- lieves that the newer tools will lay the groundwork for more ac- curate fisheries management.
“We’re trying to get decent assessments that are precise to improve forecasts in future fisheries,” says Dunlop. “This signifi- cant increase in numbers points to greater prospects for fish- ing.”
For more information about the Conuma River study, contact Roger Dunlop at Roger.Dunlop@nuuchahnulth.org or 250- 283-2012.