. The Canadian field-naturalist. 128 The Canadian Field-Naturalist Vol. 112. Figure 2. Canadian distribution of the Cultus Lake Pygmy Sculpin (Cottus sp.). The diet consists of Daphinia sp., chiromonid midge larvae and pupae, Epischura sp., ostracods, Bosmina sp., and Cyclops sp. One fish of 37 mm had consumed a smaller cottid of 14 mm in length (Ricker 1960). Predator-prey relationships are not certain. The form is eaten by Dolly Varden, Salvelinus malma, which are also confined to the deeper waters of the lake. Ricker (1960) reported up to 100 of these sculpins in a Dolly Varden stomach. Cut
. The Canadian field-naturalist. 128 The Canadian Field-Naturalist Vol. 112. Figure 2. Canadian distribution of the Cultus Lake Pygmy Sculpin (Cottus sp.). The diet consists of Daphinia sp., chiromonid midge larvae and pupae, Epischura sp., ostracods, Bosmina sp., and Cyclops sp. One fish of 37 mm had consumed a smaller cottid of 14 mm in length (Ricker 1960). Predator-prey relationships are not certain. The form is eaten by Dolly Varden, Salvelinus malma, which are also confined to the deeper waters of the lake. Ricker (1960) reported up to 100 of these sculpins in a Dolly Varden stomach. Cutthroat Trout, Onchorhynchus clarki, and Coho Salmon, Onchorhynchus kisutch, may utilize the larvae, but would rarely encounter adults as these species feed closer to the water surface (Ricker 1960). No Sculpins were found in Dolly Varden stomach con- tents from December to March (Ricker 1960), but this may reflect differences in Dolly Varden feeding behaviour than in sculpin activity. There is no indi- cation that the Cultus Pygmy Sculpins utilize Dolly Varden or salmon eggs and fry as has been noted for the parent form (Scott and Crossman 1973). The morphological adaptations (reduced bone density and increased subcutaneous lipids) are prob- ably both adaptations to vertical migrations within the upper limnetic zone (Cannings 1993). No infor- mation on parasites in this form is available. Only two parasites have been reported for the parent form, the protozoans Cryptobia lynchi and Cryptobia salmositica (Hoffman 1967). Limiting Factors The population is reproducing successfully and is probably stable although no evidence for trends is available. The species is preyed upon by Dolly Varden and Cutthroat trout and any increase in trout populations could deplete or eliminate the population. Ultimately, the major threat to the species is the transplantation of exotic species such as the Pumpkin Seed (Lepomis gibbosus) and the Catfish (Ameirus nebulosus) which could extirpate popula-
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