KREMMLING — Populations of invasive northern pike may be dropping at Wolford Mountain Reservoir, but officials say they remain a problem.
In 2008, the Colorado River District began offering a $20 bounty for each of the invasive fish caught in the reservoir in an effort to drive down populations. The number of payments claimed have declined with each year. At the State of the River meeting last week, senior water resources engineer Don Meyer also announced that recent trappings conducted along with the Department of Parks and Wildlife during the month of May snagged 56 of the non-native fish. All were young – within one year old.
“They’re apparently having a difficult time reproducing,” Meyer said.
Northern pike began showing up in Wolford Mountain’s waters in 2006. River and wildlife officials are unsure of how the fish came to Wolford Mountain Reservoir. The most probable explanation is that they were illegally introduced by anglers.
“People do like to catch them,” said Jim Pokrandt of the Colorado River District. “People will think they’re doing society a favor, and they’ll introduce species to bodies of water so they can catch the fish.”
But in reality, the pike’s introduction has caused a lot of harm.
Colorado anglers mostly prefer trout, according to a Colorado Parks and Wildlife press release issued on Friday. But northern pike are voracious predators that drive down numbers of Wolford Mountain’s more popular fish.
Recognizable by their long, cigar-shaped bodies, sharp teeth and light spots, northern pike are native to the upper Midwest. The region’s lakes have abundant supplies of forage fish and provide enough feed for northern pike. But reservoirs in the West fluctuate, and cannot sustain enough populations of these prey fish to keep the pike satisfied. To stay full, they turn to stocks of trout and kokanee salmon.
“So what happens is we’re just running a feedlot for large pike,” said Jon Ewert, biologist for Colorado Parks and Wildlife. “We stock trout and the pike live off those trout. It’s an extremely expensive way to maintain a fishery.”
Illicit introductions of the northern pike have also been documented at Green Mountain Reservoir, which is managed by the Bureau of Reclamation. A bounty for large pike is not offered there.
Ewert worries that as the large pike drive out more popular fish like trout, anglers will look elsewhere – taking their tourism dollars with them. Fishing remains an important part of the state economy. According to a 2011 U.S. Fish and Wildlife Survey, anglers spent $649 million in Colorado on trip expenses, equipment, licenses and other fishing expenditures that year.
Farther downstream in the Colorado, and within the Yampa River, there are issues with Northern Pike preying on endangered fish species that formerly thrived in the region long before Western settlement. These fish include species like the Colorado pikeminnow, bonytail chub, humpback chub and razorback sucker. The U.S. Fish and Wildlife is actively working to recover these native fish and ultimately remove them from the endangered species list.
If left unchecked, upper Colorado reservoirs like Wolford Mountain and Green could become a source for more northern pike in the Colorado River. Wolford Mountain Reservoir has surface spills most years, which Ewert said contain significant amounts of fish. If the reservoir becomes inundated with pike, they could spill down the Colorado.
“It seems far-fetched that you would have pike make it all the way down to Rifle from Wolford, but it’s an experiment we don’t want to run,” Ewert said. “If it does happen, then the implications of that are pretty severe.”
Reporter Leia Larsen can be reached at 970-887-3334 x 19603