Northern Pearl Dace - Margariscus nachtriebi
State Rank Reason (see State Rank above)
The Pearl Dace is currently listed as an "S2" species of concern in Montana because they are potentially at risk of extirpation in the state, because of limited and/or declining numbers, range and/or habitat, even though it may be abundant in some areas. Pearl Dace are not abundant when they are collected at the relatively few sites in cool, small streams and ponds they are known to inhabit. This factor, as well as introduced Northern Pike invasions into their small prairie streams, has caused them to be designated as a Montana Species of Special Concern vulnerable to extinction in the state.
The Pearl Dace is a small, native minnow of both the eastern and northern drainages within the Glaciated Plains ecoregion of Montana, and is an indicator species of the complete Coolwater Northern Glaciated Plains Fish Assemblage. Pearl Dace are not abundant when they are collected at the relatively few sites in cool, small streams and ponds they are known to inhabit. This factor, as well as introduced Northern Pike invasions into their small prairie streams, has caused them to be designated as a Montana Species of Special Concern vulnerable to extinction in the state. Unlike most of the minnows, males establish and defend territories during the spawning season. Their diet includes a wide variety of plants and animals. Pearl Dace grow to a maximum length of about 6 inches.
For a comprehensive review of the ecology, conservation status, threats, and management of this and other Montana fish species of concern, please see Montana Chapter of the American Fisheries Society Species of Concern Status Reviews.
The Pearl Dace has a dark back, sides that are dusky-silver, and a white underside. Scattered dark lines give some individuals a speckled appearance. Young have a dusky midline band that fades on large specimens but may be distinct on the caudal peduncle. Breeding males are orange-red on the sides and below. A small, flap-like barbel is present in the groove of the upper lip just above each corner of the mouth, and is sometimes absent from one or both sides. Pearl Dace have a lateral line, usually complete.
The range of pearl dace includes most of Canada, from Nova Scotia to eastern British Columbia, north to the southern Northwest Territories. In the United States, pearl dace occur from Maine south to Virginia, and across the northern tier states from New Hampshire to Montana, with relict populations in South Dakota, Nebraska, and Iowa (Menzel and Boyce 1973; Lee et al. 1980). The Pearl Dace is at the southern end of its range in northern Montana, but is considered abundant in other parts of its northeastern range.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Pearl Dace do not migrate extensively and they tend to be residents of a series of permanent pools.
Pearl Dace prefer small cool streams, either clear or turbid (Brown 1971). They spawn in clear water at depths of 1 to 2 feet over a gravel or sand bottom (Brown 1971).
Pearl Dace eat a variety of aquatic organisms including insects, crustaceans, worms, and small fish (Brown 1971).
Pearl Dace are often associated with the Northern Redbelly Dace, Brook Stickleback and Brassy Minnows in the Northern Glaciated Coolwater Fish Assemblege (Stagliano 2005). Young of the year may be associated with a aquatic vegetation for security cover, while adults generally are water column feeder. Water column feeders in these prairie stream pools are particularly vulnerable to introduced predators, since they did not evolve with them.
The species is sexually mature in two years and spawns during spring near the bottom (Brown 1971).
The management of this species should involve routine monitoring (once every 2 to 3 years) of existing populations, since there are only 12 documented in the state. The monitoring program should be designed to detect population trends, range expansion or losses and collect additional information on life history and ecology. This could be conducted while sampling for other species. The lack of proper monitoring of these populations could lead to their demise by virtue of not recognizing if and when they are in jeopardy of becoming extirpated by any artificial or natural entity.
Threats or Limiting Factors
Threats include: introduced species, especially Northern Pike, and loss of habitat from stock ponds, dams and diversions disrupting hydrologic regimes in the permanent pools of the prairie streams they inhabit.
- Literature Cited AboveLegend: View Online Publication
- Brown, C.J.D. 1971. Fishes of Montana. Montana State University, Bozeman, MT. 207 pp.
- Stagliano, D.M. 2005. Aquatic community classification and ecosystem diversity in Montana's Missouri River watershed. Prepared for Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 65 pp. plus appendices.
- Additional ReferencesLegend: View Online Publication
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- Stash, S.W. 2001. Distribution, relative abundance, and habitat associations of Milk River fishes related to irrigation diversion dams. M.Sc. Thesis. Bozeman, MT: Montana State University. 82 p.
- Stringer, A.L. 2018. Status of Northern Pearl Dace and chrosomid dace in prairie streams of Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 150 p.
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