Definition

General natural community overview

Warmwater rivers are flowing waters with maximum water temperatures typically greater than 25 degrees Celsius. They usually have watershed areas greater than 500 square miles and mean annual flow rates of more than 200 cubic feet per second. Warmwater rivers occur statewide, and include very large rivers such as the Mississippi, Wisconsin, Chippewa, Fox, Wolf and Rock, as well as smaller rivers such as the Sugar, Baraboo, Milwaukee, Flambeau and Yellow. A rich fish fauna, dominated by warmwater species in the families Cyprinidae, Catostomidae, Ictaluridae, Centrarchidae, and Percidae, occurs in these rivers.

Natural, periodic flood flows, most often driven by spring snow melt and rains, are important to the health of floodplain forests and wetlands, and to the maintenance of self-sustaining populations of wetland- spawning fish such as walleye and northern pike. The aquatic life dependent upon these rivers and their floodwaters also supports a variety of mammalian and avian species. Free-flowing, undammed rivers are a critical factor in the existence and perpetuation of widely distributed populations of certain species, especially sturgeon and several species of mollusks that require a far-ranging fish host to complete their life cycle. Dams established for a variety of purposes (power generation, navigation, flood control and recreation) caused noticeable declines in some mollusks by blocking the movement of their fish hosts.

Rare animals

Species of Greatest Conservation Need

The following Species of Greatest Conservation Need are listed according to their level of association with the natural community type, based on the findings in the Wisconsin Wildlife Action Plan.

Please see the Wildlife Action Plan, Chapter 2.4 to learn how this information was developed.

Opportunities

Management Opportunities

The following Ecological Landscapes have the best opportunities to manage for , based on the Ecological Landscapes of Wisconsin Handbook.

Major
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.

Threats / Actions

These threats and priority conservation actions were identified for the community type in Wisconsin, and they apply to all of Wisconsin's Ecological Landscapes unless otherwise indicated. Please see the Wisconsin Wildlife Action Plan, Chapter 3.3 , for more information

Threats

• Non-point source pollution resulting from urban and agricultural runoff in the watershed is degrading warmwater river habitats.
• Dams have eliminated riverine habitat, blocked migrations, fragmented populations, and created masses of sediment bearing levels of pollutants that are sometimes harmful to fish and other aquatic species.
• Point-source pollution from industrial and municipal sources (historic impact, now largely controlled).
• Alteration of the Mississippi River and the lower reaches of some Lake Michigan tributaries for purposes of commercial navigation has fragmented and degraded habitat.
• Invasive aquatic species (e.g., common carp, Asian carp, zebra mussel) are disrupting natural communities by altering habitats, food webs, and species interactions.

Conservation actions

• Improve watershed land-use practices to reduce non-point source pollution.
• Remove dams (as has been done along the Baraboo River (Sauk County), the lower Milwaukee River (Milwaukee County) and other waterways) or install effective fish passage at dams to partially mitigate dam impacts.
• Continue effective treatment and regulation of industrial and municipal discharges.
• Better regulation of existing commercial navigation activites is needed along with effective mitigation of negative impacts resulting from these activities. Expansion of commercial navigation activities should not occur unless there is scientific evidence to assure that there will be no negative impacts to riverine habitats and the species they harbor.
• Improve regulations and education to prevent the introduction new invasive aquatic species and slow the spread of existing exotic species.

Photos

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Photos

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.