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The Order Percopsiformes is a small order of North American freshwater fishes that includes three families: Amblyopsidae (cavefishes, four genera, six species); Aphredoderidae (pirate perches, one species); and Percopsidae (trout-perches, one genus, two species; Nelson 1994). Trout-perch (Percopsis omiscomaycus) are aptly named, since they exhibit characters of the salmonids, such as an adipose fin, cycloid scales, and soft fin rays, as well as characters of the percids, such as dorsal and anal fin spines, and ctenoid scales (Nelson 1994). Trout-perch are generally silvery in appearance, often with a partially transparent appearance, and relatively large heads and eyes. They are small fish, averaging 76-102 mm and ranging to 152 mm in Canada (Scott and Crossman 1973); the largest specimen from Montana was about 76 mm (Brown 1971).
The range of the trout-perch includes the Ohio, lower Missouri, MacKenzie, Yukon, and Hudson Bay basins, and the central Atlantic slope north to Quebec (Lee et al. 1980). In Montana, the trout-perch occurs in the South Saskatchewan River basin, which drains northeastern Glacier National Park and the northwestern portion of the Blackfeet Indian Reservation. Trout-perch were not reported in Montana until 1968 (Gould 1969), and the only Montana collection records are from Lower St. Mary Lake (Gould 1969; Brown 1971) and the associated St. Mary canal (Holton and Johnson 1996). Trout-perch have not been reported in other areas of the South Saskatchewan River basin in Montana, such as the Belly River and Waterton Lake, but they may occur there, as this basin has not been surveyed extensively (Brown 1971; L. Marnell, National Park Service, personal communication, October 2000). Moreover, trout-perch are commonly collected in the Belly River and Waterton Lake systems in Alberta (T. Clayton, Alberta Environment, unpublished data, January 2001). Trout-perch have also been captured in the Milk River in Alberta (T. Clayton, Alberta Environment, unpublished data, January 2001). The Milk River basin is outside of the trout-perch's native range, the species apparently gained access to the Milk River basin via the St. Mary Canal, which connects the St. Mary River system with the North Fork Milk River.
Life History and Ecology
The life span of trout-perch is three to four years (Magnuson and Smith 1963). The limited information available indicates that they become sexually mature in one to three years, and spawn from May to August in shallow waters of both lakes and streams (Magnuson and Smith 1963; Scott and Crossman 1973; Nelson and Paetz 1992). Eggs are adhesive and hatch in about 6 days at 20-23°C (Magnuson and Smith 1963). The diet of the trout-perch has not been well studied, but reported food items include chironomids, ephemeropterans, amphipods, and small fish (Scott and Crossman 1973).
In Montana, trout-perch are regularly captured in Lower Saint Mary Lake, and the Saint Mary Canal using backpack and boat electrofishing (R. Wagner, U.S. Fish and Wildlife Service, personal communication, October 2000). In the lake, they are associated with large rocky cover, and are not captured over sandy or silty substrates. During daylight periods, they appear to use rocks as hiding cover, while at night, they are out of, but in close proximity to rocky cover. In the Saint Mary Canal, trout-perch have been captured in winter after the canal head gate is closed. In the canal, trout-perch are found in residual pools, associated with large, rocky cover or concrete riprap (R. Wagner, U.S. Fish and Wildlife Service, personal communication, October 2000). Scott and Crossman (1973) report that trout-perch are typically a lake species in eastern Canada, but that it also occurs in streams, including somewhat turbid streams in western Canada.
Trout-perch are reported to undergo diel migrations into shallower inshore waters of lakes at night (Brown 1971; Eddy and Underhill 1974; Becker 1983; Nelson and Paetz 1992). It is an important forage item for game fish such as walleye and northern pike (Magnuson and Smith 1963; Scott and Crossman 1973).
Trout-perch are recognized as a Class C species of special concern by Montana Department of Fish, Wildlife and Parks and the Montana Chapter American Fisheries Society. Class C designation does not necessarily signify that a species is in decline in Montana; it is used for species with "limited numbers and/or limited habitats in Montana; widespread and numerous in North America as a whole. Elimination from Montana would be only a minor loss to the gene pool of this species or subspecies" (Hunter 1997). The Montana Natural Heritage Program's assessment of this species' status in Montana is "critically imperiled because of extreme rarity, or because some factor of its biology making it especially vulnerable to extinction," whereas the trout-perch's global status is "demonstrably secure, though it may be quite rare in parts of its range, especially at the periphery." These designations are appropriate, because trout-perch have a limited range in Montana. There is little information on the current status of Montana populations, although trout-perch were captured with minimal effort in Lower Saint Mary Lake using electrofishing in 1999 (R. Wagner, U.S. Fish and Wildlife Service, personal communication, January 2001).
In Missouri, some populations of trout-perch have been extirpated, and the species is rare and on the verge of disappearing from other areas of the state (Pflieger 1997). Pflieger (1997) considers trout-perch to be especially sensitive to pollution and sedimentation associated with row crop agriculture, as well as channelization. Trout-perch may also be sensitive to warm water temperatures because summer die-offs have been reported for some Minnesota lakes (Eddy and Underhill 1974). In Alberta, a marked decline in trout-perch has occurred in the Red Deer River, probably due to the effects of a dam built there (J. S. Nelson, University of Alberta, personal communication, October 2000). In Lower Saint Mary Lake, Montana, some trout-perch are lost to the population when they enter the Saint Mary Canal.
Trout-perch are classified as a non-game wildlife species by Montana Fish, Wildlife and Parks. They are too small to be sought by anglers. The entire known range of trout-perch in Montana is within Glacier National Park and the Blackfeet Indian Reservation. Neither entity has a specific management program for trout-perch. Surveys in the Belly River and Waterton Lake in Montana are needed to establish the presence of trout-perch in these waters.
- Becker, G. C. 1983. Fishes of Wisconsin. The University of Wisconsin Press, Madison.
- Brown, C. J. D. 1971. Fishes of Montana. Big Sky Books. Montana State University Bozeman.
- Eddy, S., and J. C. Underhill. 1974. Northern fishes. University of Minnesota Press, Minneapolis.
- Gould, W. R. 1969. First record of the trout-perch, Percopsis omiscomaycus, from Montana. Proceedings of the Montana Academy of Sciences 29:51.
- Holton, G. D., and H. E. Johnson. 1996. A field guide to Montana fishes. Montana Fish, Wildlife and Parks, Helena.
- Hunter, C. 1997. Fishes of special concern: an update. Montana Outdoors November/December 26-27.
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- Nelson, J. S., and M. J. Paetz. 1992. The fishes of Alberta, second edition. The University of Alberta Press, Edmonton, and The University of Calgary Press.
- Pflieger, W. L. 1997. The fishes of Missouri. Missouri Department of Conservation, Jefferson City.
- Scott, W. B., and E. J. Crossman. 1973. Freshwater fishes of Canada. Bulletin 184 Fisheries Research Board of Canada, Ottawa.