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pens or block nets for 6-7 days after stocking. The 2003 acclimation experiments were unsuccessful because nearly 80% of the fish died from what appears to have been acute stress. Furthermore, the calcein dye used to mark these fish failed to be visible in the field. Subsequently, Dexter National Fish Hatchery and Technology Center used this information to change hatchery harvesting and transport techniques, in hopes of avoiding stress-induced mortality in future stockings. We also eliminated the use of calcein dye, as it remains suspect in the mortality we saw, and failed as a visible field mark. Acclimation experiments in 2004 were plagued by a paucity of good habitat to hold fish. The one good habitat we did find showed early signs of success, but we were unable to trace that success throughout the remainder of the year. In 2005, instead of trying to use 10-20 acclimation areas, we scoured 18 miles of river to find what appeared to be the best areas to hold fish for a full 7 days after stocking. Early results from 2005 indicate that initial retention of acclimated fish appeared to be better than the main group of stocked fish. We have plans for additional experiments, including stocking fish at warmer water temperatures and stocking exercised fish, but are seeking input from other researchers on ways to increase the initial retention and survival of hatchery-reared YOY Colorado pikeminnow. 16. The importance of small populations as a different approach to species recovery: ideas, potential approaches, and lessons learned from Lake Mead razorback sucker investigations. Authors: BRANDON ALBRECHT and PAUL B. HOLDEN, BIO-WEST, Inc. Abstract: Historically, recovery efforts for razorback sucker in the Colorado River have revolved around the paradigm that remnant populations of razorback sucker are small, comprised exclusively of adult fish, and demonstrate little to no recruitment. In the absence of natural recruitment, recovery efforts have focused on rearing large numbers of razorback sucker for stocking. Once these fish reach a certain size, they are stocked, en masse, back into the river or reservoir. Some of the stocked fish then integrate into the wild population, if one exists, with the goal being to develop a population of 5,000 adults or more. Studies of the Lake Mead razorback sucker populations over the past 9 years have found two small populations (100-200) individuals. A non-lethal aging technique has shown that these small populations are unlike other populations in the Colorado River in that they are relatively young, and are apparently self-sustaining. Recruitment in these populations has occurred in most years since about 1970, but some years, those with higher lake levels, appear to have higher levels of recruitment. We hypothesize that the limited recruitment seen in the two small Lake Mead populations is the result of large amounts of inundated vegetation, created by long-term lake level fluctuations, along with turbidity in several key areas of the Lake. Even though lake level fluctuations affect the entire lake, and razorback sucker once spawned in many areas in the lake, recruitment has occurred in only two or three places in the lake. We believe the vegetation and turbidity provides increased protective cover for larval and juvenile razorback sucker, allowing them to avoid predation by large numbers of nonnative sport fish present in the system. 16