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Contact information
For information on Wisconsin's rare vertebrate animals, contact:
Rich Staffen
Conservation Biologist
For information on Wisconsin's rare invertebrates, contact:
Jay Watson
Conservation Biologist

Crystal Darter (Crystallaria asprella)



Crystal Darter (Crystallaria asprella), listed as a Species of Concern by the US Fish and Wildlife Service and Endangered in Wisconsin, prefers clear to slightly turbid waters over sand substrates. This darter is most often found in moderate to strong currents in large rivers where they occupy sandy riffles, bars, and pools. Spawning occurs from mid-May through mid-June?

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Crystal Darter (Crystallaria asprella). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.

Documented locations of Crystallaria asprella in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusEND
Federal Status in WisconsinSOC
State RankS1
Global RankG3
Tracked by NHIY

Species guidance

Note: a species guidance document is not available at this time. Information below was compiled from publication ER-091.

Identification: Extremely slender body with distinctly forked tail, pronounced snout and translucent body. Back and upper sides yellowish green, three or four broad saddle marks over back, 10 to 12 dark, oblong blotches along sides. Adult length: 5-6 inches (127-152mm).

Habitat: Larger, deeper rivers in clear to slightly turbid (cloudy) waters and moderate to strong currents. Prefer extensive sandy riffles, bars and pool bottoms that are clean and at least 2 feet (60cm) under water.

State Distribution: Not abundant anywhere in its range which includes: the Mississippi River, lower Wisconsin, lower Black, lower Trempealeau, lower Red Cedar Rivers, and Chippewa River in Pepin and Dunn Counties (where it is most common). A map outlining Pre-1977 and 1997 to Present Distribution is available.

Phenology: Primarily nocturnal, they prefer deeper waters during the day (6-16' or 2-5m) and move to the shallows at night or during overcast days. They bury themselves in sand with only the eyes protruding, and dart out at passing prey along the benthic (bottom) surface. Breeding behavior is unknown.

Diet: Eat mayflies, midgeflies, caddisflies, water scavenger beetles and nematodes.

Management Guidelines: This species is not easily detected using standard fish survey methods. The use of special bottom gear along with night collecting improves the chances of detection and making status determinations. Dams are responsible in part for reducing suitable habitat and can cause population isolation.



Crystal Darter

Side view adult.

Photo by John Lyons, WDNR.

Crystal Darter

Side view adult.

Photo by John Lyons, WDNR.

Crystal Darter

Alternative side view.

Photo by John Lyons, WDNR.

Wildlife Action Plan

Wisconsin Wildlife Action Plan graphic

Natural community (habitat) associations

The table below lists the natural communities that are associated with Crystal Darter. Only natural communities for which Crystal Darter is "high" (score=3) or "moderate" (score=2) associated are shown. See the key to association scores for complete definitions. Please see the Wildlife Action Plan to learn how this information was developed.

Natural community Score
Warmwater rivers 3

Ecological landscape associations

The table below lists the ecological landscape association scores for Crystal Darter. The scores correspond to the map (3=High, 2=Moderate, 1=Low, 0=None). For more information, please see the Wildlife Action Plan.

This map shows the probability of Crystal Darter occurring in each of Wisconsin's Ecological Landscapes.  Actual scores can be found in the table to the left.

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Landscape-Community combinations of highest ecological priority*

Ecological priorities are the combinations of natural communities and ecological landscapes that provide Wisconsin's best opportunities to conserve important habitats for a given Species of Greatest Conservation Need. The 10 highest scoring combinations are considered ecological priorities and are listed below. More than 10 combinations are listed if multiple combinations tied for 10th place. For more information, please see the Wildlife Action Plan.

* Ecological priority score is a relative measure that is not meant for comparison between species. This score does not consider socio-economical factors that may dictate protection and/or management priorities differently than those determined solely by ecological analysis. Further, a low ecological priority score does not imply that management or preservation should not occur on a site if there are important reasons for doing so locally.

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Issues/threats and conservation actions

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for rare animals

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Last revised: Thursday, December 22, 2022