Northern Prairie Wildlife Research Center
Even simple techniques involving construction of small rock dams and deflectors result in creation of pools and deepening of stream channels to enhance trout populations. Instream cover and bank cover also are commonly used fish habitat improvement techniques. Burgess (1985) demonstrated that in addition to increasing trout biomass, these stream habitat improvement techniques also affected populations of nontarget organisms on a study site in Quebec. Crayfish populations increased substantially in the improved section, which likely resulted in increased use of the area by mink (Mustela vison) and raccoons (Procyon lotor). These low cost fish improvement techniques may have great potential for improving habitat for invertebrate and mammalian populations in other areas.
The majority of the Tongue River restoration project in Wyoming was directed toward Instream improvements (e.g., boulder placement, riprap, slope grading) (Gore and Johnson 1979). In addition, banks were hydromulched and planted with various combinations of local riparian trees and shrubs as part of an effort to restore the fisheries. Snags consisting of pine trees anchored and cabled into the bank were found to provide the only substantial cover and habitat for colonizing game and nongame fish.
A project in west-central Colorado demonstrated that a watershed dissected by a dense gully network can be stabilized and rehabilitated by the use of check dam systems, aided by improved vegetative cover through reduced cattle grazing and plantings (Heede 1979). The dams stabilized not only the structurally treated gullies, but also gullies within the network that were not structurally treated. Comparison with untreated gullies outside the project area showed that outside gullies widened three times as much as structurally untreated inside gullies. Check dams decreased gully depth by accumulating sediment deposits. In turn, gully bank stabilization was hastened and alluvial aquifer volumes increased. This increase, plus higher infiltration rates as a result of denser vegetation, led to renewed perennial streamflow after 7 years. Within 11 years after treatment, the check dam system and improved vegetation had reduced sediment loads in the flows by more than 90%, providing a substantial benefit to farmlands and ponds downstream. From this work, Heede (1979) concluded that only part of a gully network requires structural treatment: the mainstem gully and those tributaries controlling the local base levels of others.