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Growth of cutthroat trout has been shown to be variable depending upon size, temperature, and productivity of the water. In large rivers and lakes, this species grows rather rapidly. However, in smaller headwaters, stream growth was slower (Figure 9). Cutthroat trout in Birch Creek grew about the same or perhaps slightly slower than trout in the Strawberry River, Utah (Platts 1958), tributaries to Priest Lake, Idaho (Bjornn 1957), and Flint Creek, Montana (Spindler and Bailey 1955). Trout in these streams had completed four years of growth, except in tributaries of Priest Lake. This limited age and small size of trout from smaller streams could be a function of stress placed on larger fish in limited habitat. All streams presently containing Bonneville cutthroat are very small with very limited pools that serve as deeper water habitat. Hickman (1977) reported that a cutthroat of 241 mm (9.5 inches) in length and 125 g (0.281bs) was collected in a pond with a depth of 62 cm (24 inches) and a width of 110 cm (43 inches). In Birch Creek, the deepest pool surveyed was approximately 33 cm (13 inches) with an average pool depth of less than 20 cm (7.8 inches) (Duff and Cooper 1976). Limited habitat could magnify stresses derived from lack of cover, space and adequate food. There could also be problems with accurate aging of fish using standard techniques. It is not uncommon for a fish to develop four distinguishable annuli and live for several more years without developing additional annuli. There would be considerably more overlapping of annuli as fish become older and growth was surpressed by limited environment. A combination of these factors ~~ zo is ~ 16 Z J H t4 S F 2 W J ~.~ J Q H 0 ~-- t () 6~ 6~ SCALE RADIUS (SR) IN MM X76 Figure 6. Body-scale relationship for Bonneville cutthroat trout from Birch Creek, Beaver County, Utah. 15 10 20 30 4 U