Fish biologists took a major bite out of the pike population on the Columbia River this month.
Biologists from the Ministry of Environment (MoE) and Mountain Water Research (MWR) netted close to 100 adult pike in Robson Reach over five days in a recent effort to suppress the spread of the invasive species on the Columbia River.
“Pike are non-native potentially invasive species that we’ve been concerned about for a while,” said Senior Fish biologist Jeff Burrows. “So the purpose was to check out the feasibility of suppression netting to reduce pike numbers. We don’t expect we’re going to be able to eradicate pike, there is probably a chronic supply of them coming from upstream.”
The source of the alien species is believed to have emerged from the United States and Lake Pend d’Oreille system about five years ago. Since then, the Kalispell Tribe in Spokane and Washington State Fish and Wildlife have been very successful in reducing pike numbers in the Box Canyon Resevoir of the Pend d’Oreille River using nets, so Kootenay fisheries biologists and Jeremy Baxter from MWR utilized the same process in catching Columbia River pike.
The nets are designed with different mesh sizes to trap pike at various stages of their lifecyle, yet, in the Columbia, mysteriously, no juvenile pike were caught.
“All we did catch was adults,” said Burrows. “So who knows what’s going on there.”
Although most of the pikes’ stomachs were empty, one mammoth pike that measured 90 centimetres and weighed about 19 pounds had a 40-cm. rainbow trout in its stomach.
But what is perhaps more alarming is that the netted pike were also spawning.
“That’s an issue, that there could have been successful spawning, but we’re not sure in past years. Probably they’ve tried to spawn in the Robson Reach that’s downstream of Celgar . . . but it’s not clear that smaller pike or the bigger ones are from colonizers or from entrained fish upstream. But sure it’s a concern.”
Despite catching spent and ripe spawners dripping with milt, Burrows believes the population may be smaller than at first anticipated, as the team also netted five of the tagged pike from MoE’s recent Pike Reward program.
“It’s not a very robust estimator, because populations can move around, but there might be maybe 500 adults in that lower half of the Robson Reach, so we caught a good proportion of them.”
The numbers taken in the nets also decreased over the weeks, suggesting a definite depletion in stock.
The catch rates nearly halved with every netting, said Burrrows, an excellent indicator that the team of biologists and technicians were killing a good portion of the population.
And yet another major concern for fisheries is the potential spread of the alien species into the Arrow Lakes.
“I think the jury’s out as to whether its a big problem. If that’s all it is in that reach, we can suppress them, and if we get on top of them we can really minimize it, however, if they get into the (Keenleyside Dam) lock and colonize the Arrow that would be a big problem.”
While netting has proven to be a useful and successful tool in suppressing pike populations, local fisheries will need funding to continue the process.
With Ministry resources unavailable, Burrows hopes to access funds from various environmental groups to continue the pike-suppression efforts, but, for the time being, will rely on local anglers to help keep the population in check.
There is an unlimited retention quota for pike on the Columbia and anglers are encouraged to kill all pike caught. More importantly, Burrows encourages anglers to report catches of pike outside the Robson Reach, Seven Mile, and Waneta Reservoirs, indicating time, location, date, length, and a photo if possible to confirm species. Call the Fish and Wildlife office at 354-6333.