When Dan Doutaz hears a ping in his headphones coming from the watery depths of the Columbia River, he enters another data point on the continued invasion of an unwanted species.
Northern pike – a ravenous, predatory fish that is expected to have devastating impact on native salmon and trout populations – are making their way into southern British Columbia.
It is the latest of several invasive species that have been spreading across the province, triggering concerns about ecosystem changes.
"One of the big questions about pike in the Columbia is whether or not they are getting into the Arrow Lakes reservoir and further into B.C.," the master's student at Thompson Rivers University said in an interview this week.
Earlier this year, Mr. Doutaz radio-tagged 15 northern pike he'd netted in the river. Since then, he has been tracking their movements using an array of transceivers on buoys that BC Hydro anchored in the river during an earlier study of sturgeon. Sturgeon are native to the area but are in decline.
A major concern of biologists is that pike may soon enter Arrow Lakes where they could feed on kokanee, an important sports fish that is in decline in the watershed.
There is a navigation lock on the Columbia at the Hugh Keenleyside Dam, upstream of the city of Castlegar and researchers are worried that if northern pike pass through the lock they will spread more than 250 kilometres farther north through the lake system.
"The idea [of the radio-tagging research] is if anything is detected above the dam, we can say, OK they are using the lock," said Mr. Doutaz. "And obviously that's a big management concern down the road because if they are getting into the Arrow Lakes, they have the potential to spread pretty quick."
Northern pike are native to northeast B.C. and are common throughout Quebec, Ontario, the Prairie provinces and northern territories. But they are spreading into southern B.C. by migrating up the Pend Oreille River, which flows into the province from Washington State, joining the Columbia near the B.C. border.
Northern pike are thought to have invaded Washington State, via Lake Pend Oreille in Idaho, after being illegally introduced in Montana watersheds in the 1970s and 80s. In 2011, the Kalispel Tribe, which is working to restore salmon runs in the Columbia system in Washington, described the presence of northern pike "a long-term disaster to our native fisheries."
For the past two years, the B.C. government, working in partnership with Teck Metals Ltd., which funds environmental programs near its Trail smelter, has been trying to halt the spread into Canada.
Using gillnets in the Columbia, the program has removed about 20 per cent of an estimated 700 northern pike in the area, but Dr. Brian Heise, an associate professor at TRU and chair of the Invasive Species Council of B.C., said the species is a prolific breeder and more control work is needed.
He said researchers have caught pike in the Columbia that weigh nearly 10 kilograms and many of the female fish were loaded with eggs.
"They are huge fish, up to a metre long. They have a voracious appetite. They will not only eat smaller fish, but ducks, mice, muskrats. They will eat just about anything and they produce thousands of eggs so they have the potential to reach big numbers," he said.
Dr. Heise said in addition to the northern pike, walleye and bass have also invaded the river.
Bass have been introduced in some lakes in British Columbia as sport fish, but Dr. Heise said he believes anglers have been spreading them and other species, such as yellow perch and possibly pike, by carrying them to new waters.
"At least one person has been caught moving fish in a bucket," he said. "What I would say to those people is that in lakes where [bass, pike and perch] are firmly established … enjoy the fishery there, but please don't move them from one water body to another … it's going to hurt the fisheries for [native] species."
Earlier this year, British Columbia signed an agreement with Alberta, Yukon, Saskatchewan and Manitoba to co-ordinate efforts in the fight against invasive species.