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Do fish really need to move?| A first pass at fish passage
Authorizing the free movement of fish
Can Wisconsin's dinosaurs bypass dam technology?
You're cruising down the highway, the top is down, the wind rustles your hair and everything seems perfect. Then you see one of those dreaded flashing Road Construction or Detour Ahead signs. For the car driver a detour is frustrating, but you know the route will guide you in the right direction and eventually onto your original destination.
It's different in the aquatic world, where impediments in the water truly mean "You can't get there from here."
Wisconsin has been blessed with diverse and plentiful rivers – more than 12,600 rivers and streams meander through 44,000 miles of terrain. These ribbons of life nourish and sustain the state's aquatic plants and animals.
Water flow and levels are controlled, channeled or blocked by human-built structures – usually dams – on a majority of these aquatic highways. More than 3,700 dams of various sizes have been built on Wisconsin's rivers and streams to power sawmills, increase water flow to float logs downstream, to operate grain mills, or for navigation. Larger dams generate hydroelectric power to supply paper mills, other industries or homes. Smaller dams were maintained or constructed to create reservoirs, control water levels in natural lakes, or to control floods.
Dams have been built on almost all of the major rivers in the state including the Chippewa, Flambeau, Fox, Black, Wisconsin, Peshtigo, Menominee, Oconto and Iron rivers, as well as on numerous smaller streams. A series of large dams and reservoirs – the Lock and Dam System – was constructed on the Mississippi River to maintain a navigation channel for barges. There's no denying that some dam construction has been beneficial for the state's economy and recreation. But it is equally clear that dams have impeded the movement of numerous aquatic organisms – most obviously, fish.
Do fish really need to move?
Wisconsin's river fish swim considerable distances to meet their needs. Smallmouth bass in the Embarrass and Wolf rivers migrate in excess of 50 miles between prime summer and winter habitats. Smallmouth bass in the Mississippi River migrate in spring more than 70 miles through three navigation pools on their journey up the Black River. Channel catfish have remarkable homing behavior and seasonal movements between the Wisconsin and Mississippi rivers. Returns from tagged catfish show they travel distances well over 70 miles. Lake sturgeon tagged at the mouth of the Wisconsin and Mississippi rivers have been shown to move up and down the Wisconsin River, residing for a short time (possibly to spawn) below the Prairie du Sac Dam – a journey of over 90 miles!
River fish move in search of sufficient quantities of critical habitat. Fish seek suitable refuge during periods of high or low water, in the harsh winter and during high-temperature droughts. They travel up and downstream to find food, good spawning habitat and well-protected nurseries.
Dams separate some river fish species from the habitat they need to sustain their populations. Fish populations caught behind dams become isolated and fragmented, unable to tap the genetic diversity that contributes to a population's strength.
Fishways and other methods (elevators, trapping and transferring) that allow fish to travel to their historical spawning grounds help maintain healthy, vigorous populations. Creating ways for fish to bypass dams could restore ranges for some of our high-profile, endangered or threatened species.
Providing passage for fish is important to an ecosystem as well. Barriers such as dams, culverts or dikes prevent fish from migrating or moving to a given river reach, which pose consequences for other organisms that depend on the presence of those fish. Mammals, birds, amphibians, reptiles, other fishes and invertebrates prey on fish eggs, larvae, juveniles or adults. These predator-prey relationships are important ecological interactions between aquatic and terrestrial ecosystems, and within the aquatic ecosystem itself. Such interactions can be interrupted, decreased or severed entirely when fish can no longer swim to historic portions of their range.
Here's an example: To survive and flourish, freshwater mussels rely on fish to colonize upstream habitats. Young mussels must parasitize specific host fishes to move upstream any distance. That's why fish presence and diversity reflects mussel presence and diversity in many cases. It is not surprising that some of the most diverse mussel beds are found in dam tailwater areas, where fish can no longer continue their upstream journeys.
All this being said, there are situations in which dams assist fish populations rather than block their progress. Dams have stopped the spread of piscine diseases, contained contaminated fish populations, and prevented exotic species from increasing their ranges. Dams can also stop "naturalized" non-native species like the brown trout from competing with native trout.
A first pass at fish passage
Although unimpeded fish movement in rivers was recognized as important well over 150 years ago, technology developed to effectively pass fish around or through dams has been slow, with a lot of trial-and-error. Most of the experiments had been done on the East and West coasts, where anadromous fish populations of striped bass, blueback herring, hickory shad and the Pacific salmon required free movement for reproduction. Little effort had been directed at midwestern, warmwater "resident" fish species.
The term "fish ladder" tends to have a negative connotation today because the early ladders were so ineffective in warmwater situations. This poor performance was due mainly to the general lack of knowledge of basic fish biology – how fast fish swim, what kind of water flow attracts them, and how and when they move.
From 1908 to 1912, fishways were evaluated on the St. Croix River at St. Croix Falls, the Kilbourn Dam on the Wisconsin River, the Eureka Dam on the Fox River, and the Weyauwega Dam on the Wolf River. At St. Croix Falls, not a single fish used the fishway. One sucker went through the fishway at Kilbourn. There were two bass, three pike, two suckers, one carp, 13 bowfin and one sunfish that successfully navigated the ladder at Eureka, and 49 suckers passed over the dam at Weyauwega. Understandably, none of these early fishways was considered even mildly successful. They became concrete monuments to failures of a bygone era.
How effective any given fish passage will be depends on the design, the species involved, and the site conditions. Our knowledge and understanding of fish behavior in passing around manmade obstacles has grown substantially, particularly in the last decade. Researchers have advanced fishway design by identifying critical swimming speeds and attraction flows. We now can predict with reasonable certainty how key warmwater species such as walleye, largemouth bass, northern pike and lake sturgeon will react to a fishway.
There is a considerable body of literature documenting the successes of newer fishways around North America. The Eureka fishway on Wisconsin's Fox River is one. This rock ramp or "roughened chute" constructed in 1988 allows successful migrations of a variety of fish including walleye, yellow perch, suckers and redhorse, gizzard shad and lake sturgeon.
Several fishways, used mostly by spawning fish that migrated entirely within a freshwater system of rivers and lakes, have been monitored in the Canadian provinces of Alberta, Saskatchewan, Manitoba and Ontario. Species that used the fishways included grayling, whitefish, cisco, northern pike, walleye, sauger, yellow perch, white sucker, common carp and burbot.
Several fish ladders have been constructed and evaluated at sites in Michigan; coho and chinook salmon, suckers and redhorse, steelhead, channel catfish, smallmouth bass, common carp and walleye migrate up through these ladders without difficulty. An additional 17 operating fishways (and two under construction) in Michigan target species such as salmon, steelhead, brook and brown trout, walleye and northern pike.
Authorizing the free movement of fish
Wisconsin's earliest natural resource law, promulgated by the territorial legislature in 1839, required the construction of fish passage structures on navigable waterways. Wisconsin Fish Commission reports from the late 1800s and early 1900s document public concern about the impeded movement of fish, particularly in tailwater areas. A report from 1878 discusses the fishes' inability to move back upstream and, as a result, "congregate together in large numbers at the base of dams, where they are slaughtered by the thousands by improvident men and reckless boys." Even today, it is no secret that some of our most popular fisheries are found at dam tailwaters.
Wisconsin statute states that "The department [Department of Natural Resources] may investigate and determine all reasonable methods of construction, operation, maintenance, and equipment for any dam so as to conserve and protect all public rights in navigable waters..." The definition of "public rights" has been broadly construed by Wisconsin courts to include fishing, protection of habitat, natural scenic beauty, and the protection of water quantity and quality.
Additionally, for most of the 1900s, the statute also read "...the department may order and require any dam heretofore or hereafter constructed to be equipped and operated, in whole or part with good and sufficient fishway or fishways..."
Progress on the fish passage front took a slight and unfortunate detour several years ago. The 1999 budget bill revised the almost century old statute by removing the DNR's authority to require fish passage. The department can now only require passage after two things occur: 1) rules are created and promulgated that clarify the fish passage prescription process (what, where, when, how, etc.), and 2) a cost-share program is implemented and money is available to dam owners for fish passage work.
Over the past several years, DNR staff has been working with the hydropower and paper industries, municipalities and other dam owners to develop these important rules. A process for proposing fish passages calls for a thorough evaluation of environmental benefits and includes a planning procedure with plenty of public input. Fish passage techniques may vary from changing a dam operation (for example, opening gates at critical periods) to a natural, sloped rock ramp, to a full-blown concrete structure. Costs, likewise may vary from several thousand dollars to several hundred thousand dollars.
Because dams have been constructed on public waters and many for private benefit, resource managers, anglers and public interest representatives believe the responsibility of providing funding for passage rests with the dam owner. The proposed cost-share program will require the DNR and others to ensure that financial assistance is available before fish passage can be ordered at a facility. The rules also mandate that fishways be evaluated for effectiveness and to learn how subsequent structures may be improved. The Natural Resources Board will ultimately review the rule package.
Developing rules for fishways has been long and certainly challenging. However, once the new fish passage rules are in place, the department and dam owners can begin to work cooperatively on reconnecting some of the state's fragmented aquatic habitats.
And perhaps when Mr. Walleye cruises up one of Wisconsin's aquatic highways in the future, the phrase "You can't get there from here" will only be a "passing" thought.
Karl Scheidegger is a fisheries biologist for DNR's Fisheries Management and Habitat Protection program in Madison.