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Flooding and Fish - The Effects of High Water on Wyoming's Fisheries

7/7/2014

CHEYENNE - Flooding and fish – what will the high water that Wyoming had this spring do to the state’s fisheries?

“Probably very little from a detrimental standpoint,” says Deputy Fisheries Chief Dirk Miller. “But, the potential benefits could be substantial.”

Many good things come from having lots of water, at least if you’re a fish. “In drought years, there can be setbacks to fisheries as habitats and food supplies are reduced,” says Miller. “However, the opposite is true in good water years. After years of drought, streams build up sediment on the stream bottoms. This covers important small gravels needed for the fish to successfully spawn. It also covers the important habitats for the aquatic invertebrates in the streams which are important food sources for fish.”

The high water provides flushing flows to the stream bed and washes away years of deposited silt, making available clean spawning gravels that can then be utilized by fish and the invertebrates. “More food for fish, and more places for fish to spawn successfully is a good thing for stream fisheries,” says Miller.

But, what about the high water? How do fish cope with flows that may be two or three times what they have become accustomed to?

“Over years, fish have evolved to adapt to flood situations,” says Miller. “It’s not like fish are out in the middle of a river, fighting the heavy current to keep from being washed downstream. Even in flood stages there are slow currents in every stream. The fish seek out these places and get along quite nicely. If some of the newly hatched fry or larger fish happen to get displaced by late runoff, it’s not the end of the world. Fish are a lot more mobile that many people think. After time, the fish will fill in the available habitats and the cleansed stream bottoms will provide better spawning conditions and more food sources that will benefit the fishery in coming years.”

It doesn’t end there. In recent years, drought in many western states had officials issuing cautions about the low flows and resultant warm waters in streams and the potential stress and mortality that catch-and- release angling could have on the trout caught in these waters. In years with heavy snowpack anglers usually do not have to contend with the warm water induced mortality. Heavy snowpack supplies good flows of cool water into the streams into the late summer and fall. It also provides a ground water recharge for the water table, and provides a better volume of cool water that can have a positive effect for the coming year.

Now that July is here, many of Wyoming’s streams are rounding into good fishing conditions. Because of the good snow pack it is anticipated that flows in most waters should remain good throughout the summer.

Streams aren’t the only fisheries to benefit from high water. Wyoming’s lakes and reservoirs will also benefit from good water conditions for years to come. For boaters, the benefit is obvious. Lots of water means the ramps are usable and there is more water for recreation. But aside from that, the fisheries will improve.

The good snowpack in 2011 allowed many lakes and reservoirs to return to more normal levels. But a couple below average years depleted those water levels. For the fish, when a reservoir that has been mostly dry for a number of years fills, it creates what fisheries managers call the “new reservoir effect.” When dry areas are flooded, the water becomes rich in nutrients. This in turn provides an outstanding forage base of zooplankton and scuds and other aquatic bugs favored by the fish. The result of all this food is rapid fish growth and happy anglers.

High water in lakes also creates more places for the fish to live, reproduce and avoid predation. As vegetation along lakes and reservoirs is submerged, more spawning habitats are created. Walleye, perch and other lake spawning species take advantage of the improved conditions. When eggs hatch, the young fish have cover that helps them escape predation from their larger brethren. The additional habitats also mean there will be a better production of baitfish which are an important component of fish-eating species such as walleye.

Submerged vegetation will eventually decompose and this decomposition provides added nutrients in the water which benefits plankton and in turn benefits young fish that feed on the plankton. The end result means more fish and better growth of fish.

No one likes flooded parking areas, closed campgrounds and the difficult conditions that high water years can bring. But, if looked at from a fish’s point of view – it isn’t all bad.

(Contact: Al Langston (307) 777-4540)

-WGFD-











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