Habitat diversity leads to better stream health and fishing opportunities

TU Science staff Dan Dauwalter, Kurt Fesenmyer, Tucker Porter (BLM), and John Walrath electrofishing in Goose Creek.

By Dan Dauwalter

Habitat complexity and diversity are characteristics of healthy streams. Yellowstone cutthroat trout and other native trout species have been shown to be more abundant in streams with higher habitat diversity. Simply stated, higher habitat diversity means there are more different kinds of habitats available for use by different age classes and fish species. This is why fish diversity (both number of species and how evenly proportioned they are) is a commonly used measure of stream health and restoration effectiveness.

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TU Staff Chad Chorney (left) and Dan Dauwalter (right) looking at the effect of riparian fencing on stream habitat diversity in Little Birch Creek, a tributary to Goose Creek.

TU Science Staff showed in a new study published in Transactions of the American Fisheries Society that diversity in streamflows, diversity in water depths, diversity in cover types (boulders, wood, undercut banks, etc), and diversity in streambed substrates (sand, gravel, cobble, boulder, etc) all play a role in increasing fish diversity in streams of the Goose Creek watershed located along the Idaho, Nevada, and Utah borders.  Goose Creek is on the periphery of Yellowstone cutthroat trout range.  It also has some of the highest fish diversity of all drainages in the Upper Snake River Basin because it has populations of rare suckers and chubs that are found only in Goose Creek and a few other drainages. 

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The northern leatherside chub is a fish that is only found in Goose Creek and one other watershed in Idaho.

Why is this significant?  While some studies have established linkages between fish diversity and some measures of habitat diversity, none have shown that all four of these main elements of habitat diversity – flow, depth, cover, streambed substrates – play a role in increasing fish diversity.

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Drew Reinke, one of the study authors, standing in Little Goose Creek, a wide, shallow and silted stream in poor health with low habitat diversity.

The Goose Creek watershed is impaired from various land uses as evidenced by state 303(d) lists and data on livestock trails, streambank stability, channel dimensions, and fine sediments.  One other main study finding is that streams in poorer condition have lower habitat diversity.  Why is this important?  Streams in poor health are often wide, shallow, and chock full of fine sediments from eroding streambanks that lack woody riparian vegetation (willows, alders, etc) holding them together.  As shown in this study, these symptoms of poor stream health are indicative of low habitat diversity, and low habitat diversity means unhealthy fish communities.

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Trapper Creek, in the Goose Creek watershed, is an example of high habitat diversity.

Heathy trout populations are often associated with healthy fish communities and, of course, are a requirement for good fishing.  This linkage between habitat diversity and fishing is the reason why the goal of many stream restoration projects – whether they are riparian fencing, riparian planting, or channel re-meandering projects – is to increase habitat diversity and complexity because it equates to healthier streams, heathier fish populations and communities, and better fishing.  It’s that simple.

Dr. Dan Dauwalter is the Fisheries Science Director for Trout Unlimited. He can be reached by email at DDauwalter@tu.org