Water Wolves invade the Columbia River
Northern pike is a favoured sportfish by many anglers, but Esox Lucius is also an apex predator, and when illegally introduced into non-native waters, the alien species can wreak havoc on native populations of trout, salmon, and practically everything else that swims.
The toothy, prehistoric-looking predator appeared in the Columbia River system in southern British Columbia and the Lake Roosevelt Reservoir in Washington State above the Grand Coulee Dam in 2009. Fisheries managers believe pike were illegally introduced into the Flathead Lake system as early as the 1980s, traveled through Clark Fork into Lake Pend Oreille, the Pend Oreille River, and eventually the Columbia River.
The uninvited guest breached at least 10 dams, infiltrating about 500 miles of new habitat, and is now poised to invade the Grand Coulee and Chief Joseph systems and likely beyond - into prime Columbia River salmon tributaries like the Snake, Salmon, Methow, Yakima, Wenatchee, Deschutes, Willamette, and Okanagan River systems.
Columbia’s last blue-ribbon trout water: The 30 mile section of the Columbia River between Castlegar, BC and the US border is one of the last free-flowing tail-water fisheries remaining on the 1,200-mile long river, and an exceptional native redband rainbow trout fishery. Jeremy Baxter of Mountain Water Research has led the rainbow trout recruitment program for BC Hydro for the past 20 years, and has seen the fishery make a remarkable transformation. But with pike now in the system, the redband rainbows, a descendant of the steelhead trout, are potentially at risk along with other native species like mountain whitefish and kokanee salmon.
“Everybody’s onboard in trying to control them (northern pike) . . . but it’s going to be virtually impossible to eradicate them,” said Baxter, who also leads the pike suppression program for British Columbia’s Ministry of Forests, Lands, and Natural Resources (FLNRO). “The goal is to preserve the native rainbow trout that exist in the Columbia, I mean that’s essential.”
Close to a $1-billion remediation and reclamation effort by Teck Resources (Cominco) in Trail and a Castlegar pulp mill, Zeltsoff Celgar, in the 90s drastically reduced toxic emissions and discharge of dissolved metals. Teck ceased the dumping of treated slag into the Columbia, a dense black smelting waste that carpeted the benthic habitat, adversely affecting aquatic plant growth, disrupting insect hatches, and, not surprisingly, found to be poisonous to rainbow trout and other species, putting the Columbia routinely on BC’s Most Endangered Rivers list.
“It’s such a large river, that there’s so much suitable habitat, that it was a no brainer that rainbow trout would do that,” said Baxter. “Once we figured out where they spawn and how to protect those areas with various flow regimes it seems to have worked. Now the fishery is one of the best, it’s just amazing.”
FLNRO initially changed regulations from a ‘no-fishing for invasive species’ to an unlimited pike retention, as well as introduced an angler-reward program where pike caught with PIT tags embedded in their heads would fetch the angler a $500 reward. With tepid response at best, FLNRO took a cue from fisheries biologist Nick Bean from the Kalispell Tribe of Indians Natural Resource Department (KNRD) on the Pend Oreille River and initiated the first pike suppression program ever undertaken on the Columbia.
FLNRO’s 2014 gillnetting survey netted 133 pike over 16 days in May, August, and November and estimated that the Columbia River pike population had increased to between 700 and 2,700 in a five-kilometre slack-water stretch of the Robson Reach area below the Hugh Keenleyside Dam.
The resulting “Lower Columbia Pike Suppression Report” (this section of river in southern BC is also referred to as “Lower Columbia”) found that the increase of northern pike posed several threats to the Columbia River ecosystem, including: predation of native species, and introduction of a variety of parasites and diseases. Pike also compete with other species for food reducing growth and survival, and also impede efforts to recover species at risk (SARA) such as white sturgeon, short-head sculpin, and Umatilla dace in the Columbia River.
During the 2014 study, pike weighing up to 21-pounds were captured, with one large pike having a fully intact 16-inch rainbow trout in its stomach. Seventy-six per cent of the prey was made up of salmonids (44% mountain whitefish, 17% rainbow trout, and 15% kokanee), and, in most cases, pike keyed on the low hanging fruit, exploiting each species during spawning times ie: rainbows in spring, kokanee in late summer, and in the fall, 100 per cent of the pike’s stomach contents were found to be spawning whitefish.
Gillnetting continued in 2015 with similar results, but in 2016 suppression efforts in May and June indicated that pike numbers had decreased with MWR capturing 50 pike over the month long effort.
“There may have been winter kill, or they may have moved out of the area because it’s not suitable habitat, but for whatever reason the population is down to probably less than 50 now,” said Baxter. “We’ve removed 300, so I think we’ve been successful at controlling them – the big spawning adults and as long as that is kind of maintained I think it will be a successful program.”
In early June, in the last session between net sets, Baxter spotted a large pike in the shallows and cast a fly to it. He ended up landing the largest pike of all on the fly rod - a 42-inch, 25-pound monster bursting with eggs. A mature pike can hold about six pounds of roe or about a half million eggs, give or take; a stark example of the few it would take to start a new population.
Pend Oreille Piscavores
Pike first showed up in the Box Canyon Reservoir of the Pend Oreille River in 2004 and took over, reducing populations of native cutthroat, rainbows, bull trout and cyprinids (minnows and carp) as well as non-native large and smallmouth bass before Washington Department of Fish and Wildlife (WDFW) and the KNRD took action.
"We’re a little bit different because we have so much habitat,” said Nick Bean. “But those fish have been in Montana for decades and why it took so long for them to establish down here nobody knows. We’ve had some high water years where I imagine we had a lot of entrainment into the system and they found the appropriate conditions in the spring to spawn and immediately exploded.”
Since 2012, the two groups coordinated an intensive gillnetting effort that has since culled over 17,000 pike in the Box Canyon Reservoir drastically reducing the population.
In its March 2016 pike suppression effort, the KNRD set 419 gillnets and captured 181 northern pike. In its follow up Spring Pike Index Netting (SPIN) survey conducted in May, just four pike were caught in 91 nets.
“We’ve really cropped the population down,” said Bean. “We know this was going to be a long term commitment. We have really good pike habitat here but the results indicate clearly that the program is working.”
While suppression efforts are having an effect on pike populations in the Pend Oreille and BC portion of the Columbia, downstream in the 150-mile long Lake Roosevelt Reservoir, the population is growing.
A brief six-day netting sampling in February yielded 71 northern pike near Kettle Falls and the Kettle River arm of the reservoir, compared to just 21 in 2015. While the population is relatively small, a significant number of one-year-old, two-year-old juvenile and mature pike were among those captured, indicating a breeding population is established.
Funding for Pike suppression in Lake Roosevelt was approved in May and is set to begin in 2017. Dr. Brent Nichols fisheries manager for the Spokane Tribe says between 2009 and 2011 limited numbers of northern pike were caught, but they saw an increase beginning in 2014 and a spike in 2015 and 2016, mostly in the northern reaches of the reservoir.
Washington and Oregon changed the status of pike from game species to prohibited species, permitting anglers to kill every pike they catch. However, in Montana and Idaho, they have a no-limit on pike, and are considered a game fish, with no suppression program. The pike spawn and migrate freely through the system, creating an unmitigated source for the Pend Oreille and Columbia River populations, a frustrating scenario for fisheries managers downstream.
“We knew we had a long-term commitment,” added Bean. “We have an upstream source, so that’s going to be something we’re going to be addressing in the future in high-water years when fish flush down, which is where this population came from initially.”
A breach of the Chief Joseph Dam would essentially give pike access to the anadromous steelhead, juvenile and spawning Pacific salmon and returning smolts with fish paths linking the remaining dams and tributaries all the way to the Pacific in a vast and complex ecosystem.
“We have to draw the line at Lake Roosevelt,” Nichols said at a Northwest Power and Conservation Council meeting. “That spike caused us to change our focus onto this particular species. We’re at the beginning of this population in Lake Roosevelt, so we have the opportunity to hold the line and limit the speed.”
Nichols’ remarks echo that of Baxter’s and Dean’s in the Upper Columbia and Pend Oreille, although 100 miles downstream.
For Bean, stopping pike at their source in the Pend Oreille system is the best solution.
“We are not going to remove these fish from the environment completely. We’ve got a connected system that’s huge; we’re talking about the whole Pend Oreille and Columbia system. Our intentions here now is to basically put up a wall in Box Canyon and ensure that we’re doing everything we can to make sure these fish are not impacting our local resources and those downstream on the Columbia when we’re dealing with ESA (endangered species) salmon and steelhead.”
The threat to salmon
With every breach of every dam, the invasive species emergence in successive downstream reservoirs on the Columbia seems inevitable. The extent of the Columbia River Basin below the Chief Joseph Dam is massive. The basin consumes approximately 58-million hectares with six species and subspecies of salmon, including fall, spring, and summer chinook (king) salmon, sockeye and Coho salmon, and steelhead trout, whose habitats stretch from the waters of the Pacific Ocean to the mountains of the Continental Divide bordering Idaho and Montana.
Salmon are a keystone species that supports life in the basin and contributes nutrients to streams that, in turn, support other aquatic and terrestrial species. When considering the northern pike’s effect on populations of salmonids in Alaska’s Susitna and Kenai River tributaries or in the Flathead or Davis Lake and others, the implications of a pike invasion into the Middle and Lower Columbia reservoirs is just plain frightening, but one that is also unique.
“It would depend on how frequently they would co-occur,” offered Dr. Gary Grossman, aka Dr. Trout, a Fellow of the American Fisheries Society and professor of Animal Ecology at Warnell School of Forestry and Natural Resources at the University of Georgia, in an email. “Floodplain habitats are extensively used by juvenile salmon in some systems and those are the areas that pike like too. On the other hand, certainly pike would join the list of predators lined up below fish ladders to eat out-migrants (smolts).”
Suppression efforts will elicit similar debate on implementation and administration and how to slow the invasive species spread. Delays, whether in funding, execution, or bureaucratic red tape, could impede a functional solution for the invasive northern pike, and hasten the increase of another invasive predator in successive Columbia River reservoirs.
“The amount of money that’s been spent on it, I think it’s important that they continue to try to control the population before they get out of hand,” said Baxter. “The only way to do that is to do what we’re doing. I think we’ve proven that we’re successful at capture, we’ve located where they are. We’re pretty good locating their habitat now, and if they show up in other locations, I think controlling them is the only thing we can do. It’s been working in the US to a certain degree, and so I think if we continue to do it on an annual basis then we can hopefully keep the numbers down like they are right now. We don’t know what they’re going to do year by year, so just taking one year off may tip the balance again.”
Yellowstone Lake: predator saturation
Habitat loss and degradation, and the introduction of invasive predator fish species, often through fish-stocking programs, historically are the major causes in the decline and sometimes the disappearance of native salmonids.
Apex predators like northern pike or lake trout can decimate native populations and once entrenched the invasive’s eradication through suppression efforts is extremely difficult.
“In general, removal efforts have failed although suppression is possible if you're willing to spend enough money, but eventually they'll get downstream,” said Grossman. “Overall there are few cases (maybe none) of an invasive predator being successfully removed from an open system that the public has access to.”
Greg French, author of The Imperiled Cutthroat: Tracing the Fate of Yellowstone’s Native Trout, takes a provocative look at how fisheries managers at the iconic park have historically developed and sometimes hurt its native trout habitats through the introduction of invasive predators.
“I am a passionate supporter of maintaining wild stocks of native sports fish in natural habitats,” said French. “In some cases quick eradication of ‘undesirable’ non-native species can be easily and quickly achieved, and in such cases I am generally supportive. In other cases, suppression programs are unlikely to result in eradication, and ongoing manipulation of wild systems always comes with its own set of risks, many of which are never acknowledged, much less debated.”
In Yellowstone National Park (YNP), the introduction of the lake trout aka mackinaw on Yellowstone Lake contributed to the collapse of native Yellowstone cutthroat trout populations, but low water levels and an invasive parasite also played a part in their decline. Whirling disease was found in Yellowstone Lake in 1998: a microscopic protozoan that destroys the cartilage of juvenile trout, resulting in skeletal deformities and sometimes whirling behavior when they swim, making them even more susceptible to predation.
Lake trout were ‘discovered’ in Yellowstone Lake in 1994. By 1998 the numbers ballooned to an estimated 130,000, and by 2012 that number grew to over 700,000 despite an ongoing suppression program that started almost immediately.
Meanwhile, Yellowstone cutthroat numbers collapsed from almost 2 million in 1986 to 463,000 in 2000. The decline in the keystone species kicked off a trophic cascade that impacted four species of mammals and 16 bird species that relied on cutthroat for survival.
Yellowstone Fisheries managers now spend $2 million annually on gillnetting lake trout. Early efforts of eliminating 10,000 lake trout per year were nowhere near enough to decrease lake trout numbers. The suppression numbers continued to increase and in 2015 about 315,000 lake trout were removed but with little apparent effect on the population.
The suppression effort continues in the firm belief that holding the number of lake trout at a certain threshold will give Yellowstone cutthroat a chance. But, despite the increasing lake trout population over the years, the number of cutthroat also rebounded in Yellowstone to about 1.31-million in 2012.
French believes that the inconsistent numbers of Yellowstone cutthroat are more a result of whirling disease than ravenous lake trout. Even more intriguing, a study undertaken by PhD student John Syslo, “Dynamics of Yellowstone Cutthroat Trout and Lake Trout in Yellowstone Ecosystem,” found that a dietary shift in lake trout following the collapse of the cutthroat population may have contributed to the native trout’s rebound.
When cutthroat became less reliable as a food source, lake trout began feeding on amphipods (scuds) to augment its diet. As the cutthroat population rebounded, the lake trout appetite remained largely devoted to amphipods and less so on cutthroat. This dietary shift and a growing resistance to whirling disease effectively strengthened Yellowstone cutthroat populations; however, as the population of native cutthroat grows, competition with lake trout for amphipods (also a keystone species in Yellowstone) may add further stress to the native prey’s survival.
Yellowstone National Park and fisheries managers have removed more than 2-million lake trout in 15 years and about 900,000 in the past three years.
In the Lake Roosevelt Reservoir, although a very different habitat, it is the largest lake in Washington, and the invasive pike is indeed a cause for alarm. In addition, fisheries released over 650,000 hatchery rainbow trout into the reservoir in April, and about a half million rainbow trout and kokanee annually on average.
“There’s not much (suitable habitat) but pike can survive a wide array of environmental conditions,” said Thompson Rivers University Masters student Dan Doutaz, who is studying the movements of northern pike in the Columbia and Pend Oreille. “If they can get into an area and there’s food, there’s always room for colonization of the species.”
Suppression is not always the answer and it is expensive, but according to Syslo, fisheries managers like those on the Columbia River can glean something critically important from Yellowstone Lake, hopefully before it’s too late.
“If you decide you’re going to suppress a population, go in with as much effort as you can muster initially.”
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