During times of low or no flow, river culverts and
unconnected pools, such as those shown above, are major
barriers to spawning runs for small fish, including the
endangered leopard darter.
By Craig Springer, Division of Fisheries, Albuquerque, NM
TULSA, Oklahoma--The days get longer, the temperature gets warmer, and the spring runoff subsides--all cues for the minnows and darters to move upstream. They need to find the right habitat to spawn. That salmon and steelhead do this timeless ritual is storied, but smaller resident fishes across the interior United States make spawning runs too. When you think in terms of scale, some small fishes move a long way themselves. And like bigger fish on other U.S. rivers, they run headlong into barriers.
Impediments to fish passage can come in many forms, some not so readily apparent. Take a box culvert. It may have water in it. It may look swimmable. But the flows can be too thin and too rapid, and small fish easily tire without a place to rest. Round culverts are even worse.
To remedy such a situation in southeast Oklahoma, the Oklahoma Fishery Resources Office, Tulsa Ecological Services Office, and John Hancock Timber Industries formed a partnership to open up miles of stream on commercially forested land. The threatened leopard darter in the Little River watershed is an immediate beneficiary. Removing barriers has connected habitats crucial for an imperiled fish.
"The headwater portions of Little River occasionally stop flowing, and barriers stop egress," said Brent Bristow, a biologist with the Oklahoma Fisheries Resources Office. "With the barriers gone, leopard darters can recolonize, and reach habitat they need any time of year."
Finding spawning habitat may not be the only need to move about. In small streams, fish find refuge in deep pools to ride out the winter. Getting to the same pools may mean the difference of surviving a summer when flows drop and temperatures climb. Without the access to these necessary habitats, fish populations may suffer. With imperiled fish, like the endangered leopard darter, access is everything.
The Arizona Fishery Resources Office is similarly engaged. The East Fork White River is important habitat for the threatened loach minnow and provides a recreational fishery for the threatened Apache trout. But a low-head dam that delivers irrigation water also blocked fish movement. The White Mountain Apache Tribe and the Arizona Fisheries Resources Office redesigned the dam to continue delivering irrigation water but also concentrated water midstream on the natural stream bottom at flows fish can swim through, simultaneously protecting streamside vegetation.
"The fish passage program is about connecting habitats and connecting with partners, getting the work done as a team," said Larry Bandolin, national program coordinator. "These projects in the Southwest are good examples of on-the-ground progress."
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