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. . . Swim-up fry have been held in concrete troughs (Hamman 1981a, 1989) at 20 - 210C for 2 . 3 days (Table 2.3c). Fry at CSU (1989) were held in small pans suspended in rectangular troughs. The fry were concentrated in small pans to increase feeding efficiency and to reduce time and labor in cleaning the much larger trough. AGF (1988, 1989) held fish from sac-fry to swim-up in hatchery troughs before placing them in outdoor earthen ponds. Colorado squawfish fry (Phase I) were held in fertilized recirculating systems (Hamman 1981a) and in earthen ponds 0.89 - 0.98 surface acres (Hamman 1989). Stocking rate in the earthen ponds was 105,316 - 137,438 fry per surface acre with a survival rate of 32.8% after 50 days (Table 2.3d). AGF (1988, 1989) stocked fry in heavily fertilized ponds in June at the Bubbling Pond Hatchery where the fish were held until October with variable survival and growth ranging from 2.1 to 2.9 inches. Fry have also been held in small pans suspended in troughs (CSU 1989) under intensive culture. Colorado squawfish fingerlings (Phase II) have been cultured extensively in earthen ponds, 0.98 - 1.08 surface acres (Hamman 1989). These fish fed on the natural zooplankton which was supplemented with commercial fish food starter, #1 and #2 granules (Table 2.3e). Survival of the fish in earthen ponds was 92.7% after 88 days. Phase II fingerlings have also been cultured intensively in small rectangular troughs (CSU 1989) where the fish were fed brine shrimp, Biokyowa, Ziegler's larvae, and Rangen's trout diet as part of feeding experiments to evaluate this culture technique. Humpback Chub Fewer humpback chub have been cultured and propagated in a hatchery than any of the other three species of Colorado River endangered fish. A summary of past culture efforts for humpback chub is presented in Table 2.4. Culture techniques for this species are similar to those used for the closely related bonytail chub. 2.2 - 3