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BiologyFreshwater; in the upper reaches of rivers at an elevation of 1,402-2,134 m. Ammocoetes are associated with substrates of organic detritus at water depths up to 1 m. Spawning has been observed both in lake and in stream habitats. Life span approximately 36 months; about 30 months as an ammocoete and 6 months as an adult. Metamorphosis occurs in the fall. Adults parasitic on fishes (native Gila bicolor, Rhinichthys osculus klamathensis, and introduced Salvelinus fontinalis, Salmo trutta) usually measuring much less than 15 cm TL. Because of the small size of the hosts and the deep nature of the wounds inflicted, most attacks likely result in the death of the fish being attacked. Also reported to be scavengers and cannibals. Adults apparently do not feed more than a few months. Spawning migration is very limited. Adults build redds about 10 cm wide by 3 cm deep, at a water depth of about 30 cm. The redds consist of gravel and sand. Spawning period between 17 July and 20 August in Miller Lake and 10 June in Sycan River; in the latter case, spawning occurred during mid-morning at a water temperature of 12 °C. Fecundity, 503-727 eggs/female. Adults die after spawning. The species was extirpated from Miller Lake through poisoning in 1958 because of its parasitism of planted trout fingerlings.