What happens to fish in high river waters? Are the spawning beds destroyed? Are the fish ok? Below is an explanation to these questions and more from FWP's Fisheries Research Coordinator, David Schmetterling.
In general these high flows will be really beneficial in the long run for fish. Fish in Montana have evolved to take advantage of the seasonal changes across the landscapes they inhabit. High flows from spring snowmelt creates new habitat, invigorates some stretches of river, provides nutrients, and allows fish to access areas. There are a lot of different responses to high flows, and depending on the species they behave differently. Some fish use these high waters to access areas that are otherwise inaccessible some times of the year. Also, many fish spawn during these flows, ranging from Paddlefish in the Missouri and Yellowstone rivers to many sucker species around the state. Some fish also use these high flows to trigger migrations for spawning, to find food, and move to areas where they will spend the summer. Some of these movements may exceed 200 miles. Many fish don’t leave the rivers but simply change their behaviors and avoid the high flows by moving toward the bank, where velocities are less because of the roughness of the banks. Westslope Cutthroat move from the rivers to smaller tributaries this time of the year where they will spawn with the declining flows on newly scoured and sorted substrate. Bull Trout on the other hand will use declining flows and warming temperatures in the rivers to trigger their migrations to tributaries where they spend the summer and spawn in the fall. Many insects rely on big years like this for habitat, like salmon flies. Also, in the Yellowstone River where we have experienced PKD outbreaks and fish kills, hopefully these flows will scour the rocks and redistribute the substrate and “reset” the habitat conditions that have been favorable to the intermediate host of those pathogens. Similarly, a long period of high turbid flow will prevent large algal blooms, cause by low, clear water from affecting many of our rivers. However, despite all the good things high flow years like this can have, some fish will be affected from the sediments, either causing physical trauma or from the lack of ability to feed in the turbid water.