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Big Mac Attack: Colorado Lake Trout Fishing

Big Mac Attack: Colorado Lake Trout Fishing
The best thing anglers can do to help the lake trout population on Granby is to keep a limit of trout like this. Granby currently has two to three times the number of trout found in other Colorado reservoirs. Photo by Mike Gnatkowski.

Many of Colorado's biggest reservoirs are home to huge lake trout, or mackinaws — as Coloradans call them. Lake trout were planted to provide a big-game species for anglers to target and to provide some control over less desirable species. Not many biologists will admit it, but planting lake trout may have backfired in many waters, eating rainbows and kokanee salmon as fast as the CDOW could plant them, and fisheries managers are now scrambling to keep their numbers under control.

In many lakes, biologists are encouraging, even begging, anglers to keep as many lake trout as they can. The CDOW has even resorted to netting lakers from Blue Mesa Reservoir to head off a fisheries crash. By removing trout and trying to control their numbers, the CDOW hopes to find a balance in fish populations and bolster desirable game fish populations. What was once intended to provide a balanced fishery is now becoming somewhat of a problem for fisheries managers — too many lake trout.

For anglers, Colorado mackinaws are the angler's version of big game and provide an opportunity to catch the trout of a lifetime. The Colorado state record is over 50 pounds and every year lakers topping 40 pounds are caught in places like Blue Mesa, Granby and other Colorado reservoirs. High water has benefited lake trout reproduction in recent years and exploding Mysis shrimp numbers in some reservoirs provide an unlimited food source for small lake trout. There might not be a better time to target lake trout on Colorado reservoirs.

What follows is a sampling of reservoirs that are sure to provide great trout action this season.


Lake trout thrive when water levels are high in western reservoirs. When water levels are low, exposed shorelines gather nutrients that are released once the water rises. The food chain gets a jump-start. That's exactly what has happened in recent years and lake trout populations in several bodies of water have gone bonkers. If you like to catch and eat lake trout, there may be no better time to fish, especially on reservoirs like Granby, Green Mountain and Williams Fork.

"The number of lake trout has just exploded in many of our reservoirs," claimed Hot Sulfur Springs Aquatic Biologist Jon Ewert. "Granby probably has two to three times the density of lake trout compared to other rivers with reservoirs right now. Lake trout are having a good time of it in Granby." For now, the stars are aligning for lake trout.

Mysis shrimp numbers, the main forage for small lake trout, have exploded in Granby. Granby right now is chock full of 15- to 20-inch lakers and they have an unlimited food supply. "The best thing anglers can do right how to help Granby's lake trout population is to keep a limit of small trout," suggested Ewert. Doing so might help prevent a lake trout crash in the years to come.

For now, the trout are thriving on the bounty of Mysis shrimp, but once the trout surpass 20 inches, their diet gradually switches to small fish. Most times that means kokanee salmon and stocked rainbow trout. Right now, there is barely enough kokanee salmon to sustain Granby's population of trophy lake trout, but biologists are concerned about the long-term outlook. "Right now, there's plenty of big, trophy trout to go around and they've got enough to eat," said Ewert. Fish populations in these reservoirs are in a constant state of flux. When one is on the upswing, others are in peril and likely to be on the edge of collapse. Lake trout are flourishing in Granby — for now. Kokanee salmon are disappearing. Part of that is because Mysis shrimp feed on the same population of zooplankton that the kokanee salmon thrive on.

Granby Lake has a long history of fisheries management dating back to just after 1949 when the reservoir was created. Like most reservoirs, 7280-acre Granby was very productive in its early stages. Both kokanee salmon and rainbows were planted around 1951 and lake trout were planted in 1961, and the fish thrived. Adding to the mix, Mysis shrimp were planted in Granby in 1971. Planted to be a food source for the salmon, researchers eventually discovered that the kokanee salmon didn't eat Mysis shrimp except in rare incidences, but the shrimp did eat the zooplankton that the salmon preferred. Once an extremely productive lake for kokanee salmon, Granby is now managed as a trophy lake trout fishery. But without salmon, you're not going to have giant lake trout.

Trophy trout guide Bernie Keefe said that fishing for lake trout on Granby couldn't be better the past year. "The fishing has really been unbelievable," exclaimed Keefe. "The fishing is not only been good, it's been very good. There are big numbers of 15- to 19-inch lakers for those that like to catch lots of fish and there's still plenty of trophy fish around." Keefe said ice-out provided some outstanding fishing for both numbers and trophies. Spring finds the lakers in the warming shallows chasing minnows and trout. They stay there until the surface temperature approaches 50 degrees. It's a great time to cast small crankbaits and stickbaits for trout that may be only in a few feet of water. In the fall, the process is reversed and trout move back into the shallows to feed. "October is great for numbers," claimed Keefe. "You can catch 50 fish per day. Most of them will be 15 to 19 inches."


As the heat of summer approaches, things get a little tougher on Granby. "During the summer, you had to work hard," offered Keefe. "If you targeted smaller suspended fish, you could do okay. Most days you could take your limit, but if you're targeting big fish, you had to work for them." Still, Keefe said those in the know routinely take giant mackinaws between 30- and 45-inches from Granby, fish that will tip the scales in excess of 35 pounds. Almost without fail, the anglers who catch the giant mackinaws know the lake intimately and the humps and saddles that collect summer trout. They target just trophy fish. They diligently work jigs and tubes to elicit bites from the behemoths and ignore the allure of lots of bites and limits of smaller trout. That attitude may need to change if they are to protect their trophy fishery.

While Keefe was almost giddy about the great lake trout fishing on Granby, he was the first to admit there's trouble on the horizon. "The kokanee population is about to crash," Keefe lamented. "The decline in kokanee numbers has been going on for years. It can all be traced back to a lack of zooplankton. The shrimp are eating them out of house and home." Unless there's some miraculous change in the near future, Granby's giant mackinaws could disappear.

To try your hand at landing one of Granby's giant mackinaw's contact Bernie Keefe at (970) 531-2318 or online at


Green Mountain and Williams Fork are two other reservoirs that can be counted on to provide outstanding lake trout action in 2012. "There are so many lake trout in these reservoirs right now that we've liberalized the bag limits to try and control their numbers," said Aquatic Biologist Jon Ewert. Fisheries managers have raised the bag limit on lake trout to eight fish per day on both Green Mountain and Williams Fork. Only one of the trout can be over 30 inches on Williams Fork. Most of the trout caught in both reservoirs will be between 15 and 20 inches — perfect eaters. Williams Fork offers the best opportunity for trophy fish between the two. There were several mackinaws topping 30 pounds caught on Williams Fork last spring. The potential for producing trophy fish doesn't look as perilous on these reservoirs as kokanee numbers are holding their own. One fly in the ointment, though, is the added predation by giant northern pike that reside in Williams Fork. Northerns love smooth-scaled trout and salmon, too, and big mackinaws will have to share the food supply with the pike.

A trip to Williams Fork Reservoir last year illustrated just how many lake trout are in the reservoir right now. Having never fished the reservoir before, my friend Garth LaPlante and I set a spread of divers and in-line boards to begin our search. It wasn't long before we hit on a pattern that produced one small lake trout after another. We couldn't keep them off our lines! The graph showed some big marks in deeper water near the dam, but an untimely motor breakdown prevented us from zeroing in on the big trout. Maybe this year?

1,860-acre Williams Fork Reservoir is located 3 miles south of Parshall, Colorado off U.S. Highway 40. The reservoirs is fed by two major tributaries, the Colorado River system and the Williams Fork River. Besides lake trout and kokanee salmon, Williams Fork anglers are likely to catch a hodgepodge of rainbows browns and cutthroats. There are two programs available on Williams Fork; one at the Eastside campground and one at the Peninsula Campground.

Water levels fluctuate greatly on Green Mountain Reservoir, so boaters seeking lake trout need to check on water levels before launching. Besides lake trout and kokanee, Green Mountain has a good population of both brown and rainbow trout. Green Mountain Reservoir is located 16 miles north of the I-70 Dillion/Silverthrone exit off Colo. Highway 9.


9,180-acre Blue Mesa Reservoir is Colorado's premier trophy lake trout fishery. It wasn't initially planned that way. From 1998 through 2007 the state record for lake trout was broken four times on Blue Mesa. A 36-pound brute set the standard before a 50-pound-plus giant set the record. Just last season, two mackinaws topping 49 pounds were caught in the reservoir. But Blue Mesa's cache of giant trout are in danger of disappearing.

"It's definitely not what it used to be," said Blue Mesa guide Robbie Richardson, who operates Sport Fish Colorado, (719-649-3378; "There's still a decent population, but it seems there are fewer fish, and fewer bigger fish, than there was just three years ago. The catch rates don't agree with the numbers and data claims."

A precipitous decline in the number of kokanee salmon has forced CDOW to take some drastic measures on Blue Mesa. Kokanee are the main food source of the rotund trout. A decade ago, more than 1 million kokanee salmon existed in the reservoir. Recent survey work shows that the current population estimate is only about 280,000. The population showed a slight increase last year, but it's far from the number of salmon needed to maintain a stable population. Over the last three years the CDOW has been removing lake trout to reduce predation on the imperiled salmon population. In 2009, 914 lake trout were removed, some up to 38 inches, though the majority of fish targeted are trout less than 20 inches and were taken from the upper portion of the basin. In 2010, 1,320 lake trout were captured and killed. In 2011, 1,170 trout were netted and removed, with 170 of those being trophy fish of over 30 inches. The CDOW is hoping that removing the trout will lessen predation on the frail kokanee population. Initial indications are that it's working. Last season a record 11 million salmon eggs were harvested.

Kokanee salmon were first planted in Blue Mesa Reservoir by accident. A plane headed to Morrow Point Reservoir with a load of fingerling salmon experienced mechanical problems and had to dump its load in Blue Mesa. The result was the establishment of Colorado's premier kokanee fishery. The decline can be attributed to a number of factors, but the biggest culprit is likely predatory lake trout that were introduced to the reservoir and have taken a devastating toll on the salmon population. The fact is that none of the characters in this game of musical chairs are native and maintaining a delicate balance is difficult, at best.

There may come a time when fisheries managers and anglers may have to make a choice between giant lake trout and kokanee and rainbows. But for now, lake trout fishing in Colorado is about as good as it gets. Better get while the gettin's good.

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