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S 1969); Hinckley 1973; Toney 1974; Seethaler N.D.; Behnke, 1973, and others). In general, this species has adapted to a watershed known for its variable flow, high silt loads and turbulence. Adults are big water fish, spending most of their time in eddies, pools and protected pockets just outside of the main current. Young fish are found in quieter water, usually over silt or sand bottoms. i l- Gonads begin to mature during the high runoff from snow melt (Apr June). Mature adults were once famous for their upstream spawning migrations, however, during the past 10 years no major spawning migrations have been reported. Holden & Stalnaker (1975-b) did report a general movement of squawfish into the mouth of the Yampa. ' River from the Green River, presumably for spawning. Spawning can begin when water temperatures remain above 70°F (21°C) (Vanicek and Kramer 1969; Toney 1974). The actual spawning act has never been doc~rnnted for Colorado squaw- fish, but several authors have described the spawning behavior of northern squawfish (Ptychocheilus oregonensis) (see Patten and Rodman 1969). Large schools of mature individuals congregate in pools and break into smaller groups of one female and 2-4 males for final fer- tilization and deposition of eggs. No nest is prepared. .For Colorado squawfish, egg development proceeds rapidly at 70°F (21°C), with hatching in less than four days. Newly hatched fry average 0.25 in. (6.5 mm) long ('Ibney 19 74) . Food of young squawfish consists mainly of invertebrates (zooplankton and insect larvae). When squawfish are about 4 in. (100 mm) long, fish begin to enter into their diet and by 8 in. (200 mm), the switch- , over to fish is complete (Vanicek and Kramer; 1969). With the decline of native fish populations, channel catfish have been reported as a possible deadly alternative food source. Vanicek and ' Kramer (1969) cited reports of fishermen, "Observing large, dead squawfish containing channel catfish with the spines extended and .lodged in the pharnyx or esophagus, which probably caused suffocation or starvation." Cause and effect are unknown, but high correlations exist between declining squawfish populations, declining native forage fish popula- tions and increasing introduced fish populations. Growth rates are variable and dependent upon temperature, food availa- bility, water quality and probably numerous other parameters. Vanicek and Kramer (1969) reported the calculated mean total length of age I fish from the Green River, Utah, to be 2.9 in. (74 mm), age VI 15.8 in. (400 mm) and age XI 24 in. (610 mm). 1 '