This Aug. 2015 photo provided by the Nevada Department of Wildlife shows state fisheries biologist Kim Tisdale holding one of the Northern pike removed from Comins Lake in eastern Nevada during an effort to eradicate the invasive predators. The agency is offering a $10,000 reward to help nab the suspect who apparently introduced the species into the lake again in recent months. (Courtesy of the Nevada Department of Wildlife via AP)

Nevada game wardens who spend most of their time hunting down big-game poachers are focusing on a serious threat to nature in a lake: An invasive fish species that eats all the other fish prized by anglers and then turns cannibalistic.

The Nevada Department of Wildlife is offering a $10,000 reward to help nab the culprit who apparently dumped Northern pike in Comins Lake, a popular fishing spot surrounded by mountains near Great Basin National Park.

By all accounts, Comins Lake was well on its way to recovery after the state restocked the fishery with largemouth bass, brown and rainbow trout in 2015.

But the invading Northern Pike were discovered again last month by a fisherman who caught one and called state wildlife officials. Five more have been confirmed since then.

"This malicious and illegal act seriously endangers our effort to restore this important fishery," said Jon Sjoberg, chief of fisheries for the Nevada Department of Wildlife. "The people illegally introducing pike are destroying a fishery, not creating a new one."

Chief Game Warden Tyler Turnipseed announced the reward this week.

"We intend to find who did it," he said.

Northern pike may not sound as scary as piranhas or the Asian swamp eel—two of the other half-dozen fish that Nevada law singles out as invasive, injurious aquatic species.

But with its long, needle-sharp teeth, the voracious predator that sometimes grows longer than 4 feet (1.2 meters) can wipe out an entire fishery.

"They eat all the trout we put in there," Edwin Lyngar, spokesman for the state wildlife agency, said in an interview Friday. "Then they eat all the other fish they can find, and then they start to eat each other."

The remote eastern Nevada lake near Utah border covers about two-thirds of a square mile (1.7 square kilometers) and draws numerous anglers.

"It brings tremendous economic activity to this part of the state," Lyngar said. "Years ago, people came from all over the world to fish that lake."

At its peak in 2004, the lake logged 35,000 "angler user days" and generated more than $2 million for the local economy as the fourth-most visited fishery in the state behind Lake Mead, Lake Mohave and the Truckee River, which flows out of Lake Tahoe through downtown Reno. That fell to about 2,000 user days and $73,000 by 2013 as the non-native pike took over.

The reward money was donated by several sportsmen's groups, including Nevada Bighorns Unlimited and the Operation Game Thief Citizens Board. If officials catch a suspect, the person would face criminal penalties.

Lyngar did not want to speculate on the perpetrator's motives.

"But we've had people put pike in waterways before because they want to catch pike. They are a good fighting fish," he said.

Authorities also cannot rule out a distant possibility that the fish found some natural way to get into the lake.

"Anything is possible, but the evidence indicates very strongly that is not the case," Lyngar said. "We believe very strongly they were introduced by someone on purpose."

Lyngar said state biologists are doing everything they can to stop the pike before they get a toehold and they've seen no evidence of any survivors since they netted the last four during an extensive electrofishing effort last week.

A biologist "told me he doesn't mind if one is left," Lyngar said. "But if there are two, we're in trouble."

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