The Stream Doctor

September 22nd, 2003

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.

Q. From STUART LENT: During flooding, when streams and lakes overrun their banks, what happens to the fish and are there any changes to the way to fish these streams and lakes?

A. I'll handle the first part of this, but leave the fishing strategy to those folks that field those kinds of questions.

Flooding in streams is usually of more consequence to fish than flooding of lakes. In the latter, it is mostly a case of fish in the lake following the overflowing water. Then it is a matter of where they end up when the water recedes. If they find there way into a river bed and can live there, they might survive. If they get left stranded, they either die when the water disappears or if stranded in pools, may die when the water heats up to lethal temperatures.

Survival of fish, or any other aquatic organisms for that matter, during floods in streams is a much greater traumatic episode and depends on several factors, two of the most important being the severity of the flood and the presence or absence of refuges or obstructions in the water where they can find shelter from the force of the flooding water.

It is quite surprising to find that fish and other organisms can survive floods which one would guess they had no chance in. Most of this is related to the fact that large rocks, trees, still waters or eddies at the edge of the stream, depressions in the bottom, and other such structures provide a refuge so that the organisms can escape the force of the water current. Of course this won't work if the flood is of such force that it moves these objects and thoroughly scours the bottom. Then, the organisms are either displaced downstream or killed. As I said, survival can be remarkable. I've studied a small cold-desert spring stream that normally is about 3 ft. wide and 4 inches deep. In certain winters when chinook winds rapidly melt the snow, the stream grows almost instantly to 60 ft wide and about 12 feet deep - a real arroyo gully-washer! Yet within a day or so of the stream returning to normal flows, which is very quickly, you can find populations of chironomid larvae and damselfly larvae in the stream; there are no fish. It's hard to believe anything could survive.

Although I'd rather defer the "how to fish" part of the question to those who answer these questions, a couple of things are obvious. First, if you're trying to fish them while they're flooding - be careful. Second, water conditions will likely be disturbed with the water quite turbid from suspended sediments. Thus, you need a lure that is highly visible and one fished where they fish are - on the bottom or behind obstructions. Third, the fish may be more concerned with living than feeding, so probably won't be feeding regularly.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at

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