Using Tiger Muskies to Protect Hatchery Fish

Tiger muskies can be a trophy catch for anglers, but they’re also a good tool for managers that want to control populations of suckers or other fish that compete with trout or other popular sport fish.

The trick is figuring out whether the toothy predators — a sterile cross between true muskellunge and northern pike — are eating the suckers or developing a tastes for expensive stocked trout. That seems to be the case in Colorado, according to a study published in the journal Lake and Reservoir Management.

The state has stocked tiger muskies in reservoirs to control white suckers where they compete with hatchery-raised rainbow trout and other salmonids. Yet it wasn’t clear exactly how the tiger muskies were responding to food web structures in the state’s lakes, according to Jesse Lepak, an aquatic research scientist with Colorado Parks and Wildlife.

“We’re stocking tiger muskies in lakes where there are a lot of white suckers that we would like to control,” Lepak said. “But if there is other forage available, will they consume those or will they eat the white suckers as we intended them to do?”

State biologists posed that question to Lepak, who followed up on leads of recent tiger muskie catches to pick five reservoirs to study. The five reservoirs — Big Creek, Clear Creek, De Weese, Parvin and Pinewood — all had naturally reproducing populations of white suckers and stocked salmonids like rainbow and cutthroat trout and kokanee salmon.

Measuring a tiger muskie from a Colorado reservoir (Credit: Jesse Lepak/Colorado Parks and Wildlife)

The researchers sampled muscle tissue from tiger muskie, suckers and trout from the five reservoirs and used chemical tracers to see what proportion of the muskie’s diet was made up of suckers and hatchery-raised fish.

While the suckers carry a chemical signature associated with the freshwater lakes in which they’re born and raised, the stocked salmonids leave a chemical signature associated with marine systems — a holdover from their days in the hatchery eating pellets made up of ocean species.

The results of the study indicate that the muskies were eating more stocked salmonids than white suckers in every reservoir. “It wasn’t 100 percent hatchery forage or anything like that, but there were cases where it was a higher proportion of hatchery fish than others,” Lepak said.

The news that tiger muskie don’t avoid eating valuable stocked fish will help the state’s fisheries managers identify systems and situations where the tiger muskies are going to work best, Lepak said. In the meantime, tiger muskie are a sought-after sport fish in their own right in Colorado, where the state record is a 53-inch fish weighing in at 40 pounds and 2 ounces that came from Quincy Reservoir.

“They’re a valuable fish,” Lepak said. “When someone catches a big tiger muskie, you tend to hear about it.”