Flooded farm fields provide sanctuary for native fish species. Photo by Guillermo Giannico, OSU.
There’s no question that winter and spring floods in the Willamette Valley cause considerable problems for homes, businesses and farms. But they’re good for at least one species… fish.
Research done at Oregon State University shows that flooded farm land helps fish in several ways. It gives them a sanctuary from fast moving flood waters and safe places for breeding. It also provides access to new sources of food.
Historically speaking, farms are relatively new to the valley. Until white settlers arrived the valley floor was mostly prairie. Yet in the last 200 years or so, native fish have evolved along with the change from prairie to farmland.
“Floods have always been a dynamic part of the system, much the same way that snow is for elk in Yellowstone,” says Guillermo Giannico, a freshwater fish ecologist at Oregon State University. “Over time, animals will adapt to get the most out of their habitat. We have found that native fish have adjusted their behavior to use these floodplains, mostly in agricultural lands, to great benefit.”
OSU Researchers Guillermo Giannico (left) and Randall Colvin (right) at work. Photo by Lynn Ketchum, OSU.
Giannico and the other researchers found 13 types of fish using flooded fields from December through May. Most of them are redside shiners and threespine sticklebacks, but they also found tiny Chinook salmon and cutthroat trout.
Just because some of these fish aren’t exactly household names, Giannico says they’re still important.
“The fish that are caught in the Northwest for sport or commercial reasons do not thrive in isolation,” he says. “All of these species are part of an interconnected food web. Some are prey for salmon and steelhead; others compete with them for resources and habitat. Most consume insects and other invertebrates that are surprisingly diverse and abundant in the waters, grasses and shrubs of the floodplain.”
The research may affect how we manage farm land. For starters, Giannico says grass seed and other farmers may not be having quite the negative impact on fish as we once believed. In some ways what they do helps fish.
But not all farm land is created equal, as far as the fish are concerned. Flood waters withdraw faster from farms with deep drainage ditches, giving the fish less time in their temporary homes in the field. Many of the fish studied do better with meandering, shallow ditches that run through woods and shrubs.
Giannico says many farmers are just beginning to understand this, and are willing to look at making changes that might help.
“Now we’re working with farmers to see if we can have the best of both worlds – a system that allows farmers to maintain productive fields while at the same time encouraging optimum habitat for aquatic species.”
