. The Canadian field-naturalist. 156 The Canadian Field-Naturalist Vol. 112. Figure 3. Canadian distribution of the Chiselmouth, Acrocheilus alutaceus (after Cannings 1993). obtained by scraping filamentous algae and diatoms from rocks and other substrates with the chisel-like lower jaw (Scott and Grossman 1973). Large amounts of filamentous algae and diatoms are con- sumed, but Moodie (1966) found no evidence that the algae was digested and concluded that diatoms were the major food. Limiting Factors The apparent requisite for water temperatures above 17°C may limit the distribution in the co
. The Canadian field-naturalist. 156 The Canadian Field-Naturalist Vol. 112. Figure 3. Canadian distribution of the Chiselmouth, Acrocheilus alutaceus (after Cannings 1993). obtained by scraping filamentous algae and diatoms from rocks and other substrates with the chisel-like lower jaw (Scott and Grossman 1973). Large amounts of filamentous algae and diatoms are con- sumed, but Moodie (1966) found no evidence that the algae was digested and concluded that diatoms were the major food. Limiting Factors The apparent requisite for water temperatures above 17°C may limit the distribution in the cooler streams of higher altitudes in British Columbia. Young fish have a diet similar to that of young Squawfish {Ptychocheilus oregonensis). Competition for food at this stage of the life cycle might be limit- ing in some areas where larger concentrations of Squawfish occur in the same watersheds (see Scott and Crossman 1973). Bangham and Adams (1954) found fish from British Columbia infested with the nematode Rhab- dochona cascadilla, the trematodes Posthodiplo- stomum minimum and Neascus sp., and Gyrodacty- loidea. Hoffman (1967) provides information on other parasites, but no evidence as to whether they are limiting. The Chiselmouth is not known from reservoirs in British Columbia. Impoundments may prevent upstream movement and the species does not survive in deeper waters above the dams (Cannings 1993). Slatick and Barham (1985) found that Dennil Fishways of 20 m or more in length prevent upstream movement of cyprinids, including Chiselmouth, but shorter fishways could be passed. Special Significance of tlie Species The species is of little or no economic importance, but is of biological interest because of the unique adaptation of the jaws and utilization of primary pro- ductivity. At one time, the species was apparently used by aboriginal people for food (La Rivers 1962). Evaluation There is very limited information on this species, its scattered distribution or possible
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