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Montana Field Guide

Montana Field Guides

Brassy Minnow - Hybognathus hankinsoni

Potential Species of Concern

Global Rank: G5
State Rank: S4
* (see State Rank Reason below)

Agency Status
USFWS:
USFS:
BLM:


 

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State Rank Reason (see State Rank above)
The brassy minnow is currently ranked an S4 in Montana and is considered a potential species of concern. While this species is apparently secure, it may be quite rare in parts of its range, and/or suspected to be declining.
  • Details on Status Ranking and Review
    Brassy Minnow (Hybognathus hankinsoni) Conservation Status Review
    Review Date = 04/08/2010
    View State Conservation Rank Criteria
    Population Size

    ScoreU - Unknown

    CommentUnknown.

    Range Extent

    ScoreG - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)

    Comment213,883 square kilometers based on Natural Heritage Program range maps that appear on the Montana Field Guide

    Area of Occupancy

    ScoreE - 100-500 km squared (about 25,000-125,000 acres)

    Comment470 square kilometers based on Heritage range maps and occupancy of 1% of landscape by streams and occupancy of 22% of sites surveyed.

    Long-term Trend

    ScoreE - Relatively Stable (±25% change)

    CommentEven though they have been impacted by grazing, exotic species, and some dewatering, prairie streams have probably been pretty stable in terms of water etc. since the arrival of Europeans within +/-25%

    Short-term Trend

    ScoreE - Stable. Population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation

    CommentSince 1999, prairie fish surveys do not suggest decline as indicated by distribution data although this is not as sensitive to detecting decline as regular monitoring of a network of sites.

    Threats

    ScoreF - Widespread, low-severity threat. Threat is of low severity but affects (or would affect) most or a significant portion of the population or area.

    CommentIntensive agriculture, overgrazing, road crossings, dams, and exotic species (Northern Pike in particular) all represent threats.

    SeverityLow - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.

    CommentSpecies is capable of recovering quickly if suitable habitat is available. Perhaps the majority of prairie streams affected by intensive agriculture are capable of recovering to the point of supporting populations within 50 years.

    ScopeModerate - 20-60% of total population or area affected

    CommentOne third of Brassy Minnow Range is subject to the presence of Northern Pike. Intensive agriculture probably threatens the species in 20% of its Montana Range. Intensive grazing is much more patchy, perhaps 5% of species range in Montana.

    ImmediacyModerate - Threat is likely to be operational within 2-5 years.

    CommentOngoing

    Intrinsic Vulnerability

    ScoreC - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).

    CommentLongevity of 3-4 years

    Environmental Specificity

    ScoreC - Moderate. Generalist. Broad-scale or diverse (general) habitat(s) or other abiotic and/or biotic factors are used or required by the species but some key requirements are scarce in the generalized range of the species within the area of interest.

    CommentPresent in a variety of prairie stream sizes and substrates. Trend toward clearer streams, but seem to handle a variety of turbidities as well.

    Raw Conservation Status Score

    Score 3.5 + 0.0 (area of occupancy) + 0.0 (environmental specificity) + 0.0 (short-term trend) + 0.0 (threats) = 3.5

 
General Description
As its name implies, live specimens of the brassy minnow have a greenish-brassy color. This native species lives in warm-cool water prairie streams east of the Continental Divide in Montana. It is more frequently collected in smaller and clearer perennial streams than the western silvery or plains minnow. Close associates found with this species include the brook stickleback, lake chub and northern redbelly dace. Its herbivorous food habits are probably similar to western silvery and plains minnows. Brassy minnows are somewhat smaller than its sister species, only reaching a length of about 4 inches.

Diagnostic Characteristics
The back of the brassy minnow is olive-green to brown, the sides are yellowish or dull silver becoming brassy in adults, and the underside is white. A dusky midside stripe is usually present.

Species Range
Montana Range

Click the legend blocks above to view individual ranges.

Western Hemisphere Range

 


Range Comments
Native range includes the Missouri, Platte and Mississippi River drainages, from Canada, Montana and North Dakota south to Colorado, Kansas and northern Missouri; Mississippi River from mouth of Missouri River upstream to Illinois and Michigan. In Montana, this species is found east of the continental divide in streams of the Northern Prairies and Northwestern Great Plains Ecoregions.

Summary of Observations Submitted for Montana
Number of Observations: 696

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
The brassy minnow favors the upper reaches of creeks characterized by no current, silt or mud bottoms, and aquatic vegetation in southeast Montana. They prefer clear, slow streams but have been collected in larger rivers with higher turbidity, and occasionally in lakes.

Food Habits
Brassy minnows are herbivorous. They feed mainly on diatoms and other algae, which it scrapes from the bottom or off aquatic vegetation.

Ecology
These fish tend to be abundant in habitats with few predators, as they seem to be very vulnerable to fish predation.

Reproductive Characteristics
Brassy minnows probably spawn in the second or third year during May through July.

Threats or Limiting Factors
Threats to this minnow species is largely from introduced predatory fishes, such as northern pike and walleye

References
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Citation for data on this website:
Brassy Minnow — Hybognathus hankinsoni.  Montana Field Guide.  .  Retrieved on , from