Flaming Gorge fish feasting on kokanee

Posted: Wednesday, June 12, 2002

DUTCH JOHN, Utah (AP) -- As the kokanee go, so goes Flaming Gorge. That's the way things are right now.

But it hasn't always been this way. Over time the focus has switched around from browns to rainbows, then to chubs and smallmouth, and now it's kokanee salmon and trophy lake trout ... Mackinaw to some.

At present, the kokanee are maintaining a balance in the lake by keeping lake trout alive and fishermen happy. This natural balance, however, could turn around and rather quickly. It has before.

The giant browns have vanished.

At one time the world record brown was a Flaming Gorge fish. Also gone are the giant rainbow. At one time the lake was also filled with Utah chubs. Fishermen hated them, but predator fish thrived on them. The really big fish, 30 pounders and larger, grew into giants by eating chubs.

The problem is they've eaten all of them. So, for now, the predators have to feed on kokanee. The problem is the kokanee haven't been able to fill all the voids left by chubs.

And until the kokanee get to a point where they can completely restock the pantry, the smaller fish have much less chance of ever reaching giant size.

''There are still some big fish; that is, fish over 30 pounds, in the lake. We had one that was nearly 50 pounds caught last year. But, my sense is that these fish did most of their growing when there was an abundance of chubs and kokanee,'' responded Roger Schneidervin, special projects biologist at the Gorge.

''I think we're going into a period of time now when the lake is not going to produce the monster fish it once did ... not until the kokanee take off and reach their potential. Fishermen are simply not catching as many 30-pound fish.''

The kokanee are running on a natural two-year cycle two up and two down. This is the second year of the up cycle. But, even in the best years, the kokanee are nowhere near the levels the Utah chubs were when trophy fish were more common.

''Modeling tells us that we can increase the kokanee population in the lake two to three times and still have plenty of food for them to survive,'' said Schneidervin. Pressure from predation and sportsmen, however, seems to be limiting growth.

Last week, Schneidervin began annual gillnet surveys on the lake. In the early hours of the morning, nets were dropped at different depths in order to sample a variety of fish. The first nets were dropped in Antelope Bay to snag large lake trout. Smaller-mesh nets went in later in the week to sample other species, such as smallmouth, rainbow and smaller lake trout.

On the first pass, four wide-mesh nets were dropped mid-water at depths between 60 and 90 feet. Nine fish were caught, weighed, measured, checked for plumpness, then relieved of their morning breakfast in order to sample food sources, and released. The smallest fish caught was 7 pounds and the largest 24 pounds. Two fish in the 20-pound class broke loose and swam away.

''Getting this information will give us a pretty good idea whether or not the lake trout are getting enough groceries,'' he said as he maneuvered the boat into position to pick up the first net. ''Between Utah and Wyoming, we'll sample a representative area of the lake and end up handling around 200 lake trout.''

Thus far, the netting has supported the obvious, that chubs have all but been wiped out and speculation that the lake is no longer able to produce the trophies it once did. Biologists have also documented a rising population of white suckers in the reservoir and an overpopulation of smallmouth.

One finding from the netting, said Schneidervin, has him concerned. That is that there is a strong age class of lake trout about to reach fish-eating size, which will result in even greater pressure on the kokanee.

''Which is why we are still encouraging anglers to keep fish, particularly the smaller and medium-size lake trout,'' he added.

A parallel study being conducted by Tyler Haddix, a graduate student at Utah State University, involves the diet of the fish in the reservoir and possible stunting, or limited growth, of rainbow in the lake. As with lake trout, the question centers on food. Part of the study will involve measuring the gill structure of rainbow to see if it differs from that of kokanee, and then determine if it allows the rainbow to utilize a range of zooplankton in the lake sufficient for rapid grow.

''We're not getting the growth out of the rainbow in Flaming Gorge that we should. It's the same problem in some of the other Utah reservoirs,'' said Haddix. ''The interesting thing here is that at one time this reservoir had some really big rainbow.

So, for now, those anglers heading for Flaming Gorge this year can expect to have good fishing for smallmouth and kokanee Schneidervin said it appears now that the kokanee is the most popular yield fish in the lake and, occasionally, may catch a trophy Mackinaw, albeit less frequently.



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