Sicklefin Chub - Macrhybopsis meeki
The sicklefin chub is a rare, large-river minnow species found in the lower Missouri and Yellowstone Rivers (Large Valley River Ecosystems) of Montana. It was first collected in 1979, and to date has only been found in about a dozen river segments. Because it is rare and specialized to this large river system, it is a Montana Fish of Special Concern. Its general habitat and distribution is much like that of the sturgeon chub. The sicklefin chub is found in large, turbid streams in the plains region of Montana. This species is very similar in appearance to the sturgeon chub except that its pectoral fins are strikingly long. The life history features and maximum size of the sicklefin chub are similar to those of the sturgeon chub.
Sicklefin chub are light brown on the back and upper sides and silvery-white below. There is a conspicuous barbel at each corner of the mouth.
Summary of Observations Submitted for Montana
Number of Observations:
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(Records associated with a range of dates are excluded from time charts)
Sicklefin chub are strictly confined to the main channels of large, turbid rivers where they live in a strong current over a bottom of sand or fine gravel (Pflieger 1975).
Unlike the sturgeon chub, all of the Montana captures have been from only the Missouri and Yellowstone rivers, indicating a strong preference for large turbid rivers (Montana AFS Species Status Account
The species is probably a bottom feeder which locates its food primarily by taste (Pflieger 1975).
Montana apparently marks the upstream limit of the sicklefin chub's range (Holton 1980, 1990).
The species reaches a maximum age of 4 years and generally becomes sexually mature at the age of 2. Spawning occurs in main channel areas of large, turbid rivers which they inhabit. The spawning period is in the summer months and probably occurs over a wide time span, similar to other big river species. Although sympatric, there is no information that suggests this species hybridizes with the other member of its genus, the sturgeon chub (Macrhybopsis gelida
) (Montana AFS Species Status Account
The management of this species should involve routine monitoring (once every 2 to 3 years) of existing populations. The program should be designed to monitor 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. Recommendations for operating reservoir and irrigation projects should be developed for improving and maintaining sicklefin chub populations and habitats in Montana (Montana AFS Species Status Account
Threats or Limiting Factors
Major threats to the sicklefin chub and other large river fishes are habitat and flow alterations from dams, diversions, irrigation operations and riparian development (Rinne et al. 2005). Sicklefin chubs need main channel gravel and sand runs in turbid running waters for their life history requirements(Pflieger 1975), thus decreased flows and excessive siltation of gravels are threats facing all lithophilic spawning fish species (Waters 1995). Reservoirs created behind dams inundate riverine habitats and replace the river with lentic conditions, which is unsuitable habitat for sturgeon chubs. Dams also create unsuitable habitat for sicklefin chubs downstream by reducing turbidities and/or altering temperature and flow regimes (Ruggles, pers. comm). Fortunately for this species, it appears unlikely that any new dams will be built on the Yellowstone or Missouri rivers in Montana in the foreseeable future. However, water regulation at Fort Peck Dam and several other tributary dams (Intake on the Yellowstone) continue to limit the distribution and abundance of some fish populations in Montana by fragmenting populations and restricting spawning and migration patterns (Ruggles, pers. comm., Rinne et al. 2005).