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I tured when approximately 460-510 mm in length; the males at five years of age; the females, at six years (Roger Hamman, personal communication). Size at maturity in river and hatchery populations thus appears to be in general agreement, though age at maturity may be earlier in the Dexter NFH population, perhaps due to a faster growth rate (Dexter fish were of known age; age of Seethaler's (1978) river fish were calculated by scale-annuli analysis and thus could have been in error). This would suggest a fixed size-at-maturity rather than a fixed age-at-maturity for the species. Results from West Pond are therefore unusual, suggesting a high degree of plasticity for age and size at sexual maturity in Colorado squawfish (see Stearns and Crandall 1984). Under certain conditions, maturation of squawfish may occur at earlier age and smaller size than previously re- ported. Though only 13.3% of the squawfish we sampled showed signs of maturity at age III, we presume that more would have been in breeding condition the following year at age IV; however, our treatment of the pond with rotenone in fall 1989 precluded determination of this. Perhaps future examination of gonads of preserved squawfish from West Pond can provide additional information. Survival General. Survival of squawfish in West Pond was difficult to assess until the pond was rotenoned in late 1989. Because of steep banks around the majority of the pond, only one corner of the pond could be effectively seined. In early June 1987, a large school of squawfish was found in a shallow cove (2-15 cm deep) on the north side of the pond. These fish may have been attracted to the warmer water of the cove, which was 2-3 C warmer than the remainder of the pond. We blocked off the cove and seined nearly all the squawfish present. By counting and weighing a subsample 25