Flood Effects on Fish

As I mentioned, Indiana finally got a good shot of rain this past week with more expected by weekend. I took the time to get out on a creek and do some fishing with a friend, and the conversation at some point got around to flooding effects on bass spawns and populations in general. So I've gathered some research and compiled it here for your reading.

Our drought conditions this year have resulted in great spawns for river bass of the brown persuasion. Lots of YOY running around all over the state from all the reports I've gathered. But heavy rainfall in certain parts of the state have prompted flood warnings, and the question becomes one of what will happen to those good spawns. Research suggests we need not worry too much at this point.

• Susceptability of Young-of-the-Year Fishes to Downstream Displacement by Flooding
• Critical Stream Velocities for Young-of-Year Smallmouth Bass in Relation to Habitat Use

It seems that there is a critical period of growth that fish need to get through in order to successfully cope with flood waters. Any fry much under 1/2-inch are extremely vulnerable to flooding. As those fry grow from 1/2-inch up to the 1-inch range, they quickly gain swimming ability. By the time they have met or exceeded that 1-inch size, as all have probably done easily by now, they are quite capable of fending for themselves. So this is good news.

There is also some nice research to show that another issue might be tied to sudden water temp changes. The warmer the water the better fry and fingerlings can swim. Warm flood pulses would actually increase the ability of YOY fish to survive. Cold pulses will slow down their ability to swim, but probably not to the level of being a disaster.

• Effects of Temperature Acclimation on the Swimming Ability of Smallmouth Bass Fry
• Swimming Performance of Three Warmwater Fishes Exposed to a Rapid Temperature Change

And if research on trout is any indication of a basses ability to cope, it takes a major catastrophic flood to negatively affect adult populations. Even so, in this worst case scenario trout were able to effectively rebound and repopulate all decimated stream areas within 3-4 years, sometimes actually exceeding pre-flood populations. Additionally, growth rates for the newly populated improved due to the lack of competition from a large population of fishes.

• Response of a Brook Trout Population and Instream Habitat to a Catastrophic Flood and Debris Flow
• Effects of Floods on Trout in Sagehen Creek, California

In the end, I'd like to think that our bass are just a bit tougher than those trout ;) and that we'll have some really good years of fishing ahead of us to look forward to.

Comments

[Ziert]

For the discriminating fisherperson: Not so hidden in here is the average effective retrieve speed of lures under various water temp conditions.

I.E.: While water temp may slow or speed up swim speed, it does not equate to fish activity reletive to easy prey and/or nearby food. Therefore, water temp should be noted as how far or near we have to be in our bait presentations and at what speed those presentations should develope.