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On the Green River, all bonytail were released at Green River State Park (RM 120.0), approximately 16 river miles below Desolation/Gray Canyon. Monitoring occurred from RM 136 down to RM 0 at the confluence with the Colorado River (Figure 1). METHODS Hatchery Production The broodstock being used to reintroduce populations in the UCRB is maintained at Dexter National Fish Hatchery and was established from a relict population in Lake Mohave. Eggs are fertilized and hatched at Dexter, bonytail fry are then transferred to Wahweap State Fish Hatchery where they are reared to release size in ten ponds. Growth rates depend highly on fish density in the pond. In the initial two years of the study, the target size for bonytail after their fIrst summer at Wahweap was 120 mm TL with a range of 65-170 mm TL. After a second summer growing season at Wahweap, fish averaged approximately 300 mm TL. When the study switched from working off of the Reintroduction Plan (1996-1997) to the State of Utah Stocking Plan (1998 and on), the stocking number increased. This increased production resulted in increased fIsh density at the hatchery and growth rates plummeted. The study design was severely compromised at this point; by the last year of the study it took two years in the hatchery to produce a 130 mm fish. Wahweap also oversaw the marking of all bonytail before their release. From 1996 through 1998, all released bonytail were PIT tagged. During this period, all fish were weighed, measured, tagged and returned to the grow-out ponds one to two weeks prior to stocking. In 1999 through 2001, production was stepped up and less expensive coded wire tags (CWT) were implanted in all stocked fIsh. During this time period, only a sub-sample of one or two hundred fish were weighed and measured at the release site. Retention of coded wire tags was examined in fIsh tagged in 1999 and then held over winter. Retention was 98% on the first 100 fish examined and subsequent spot checks have averaged 95% (Gustaveson and Bradwisch 2001). The drawback of the CWT is that individual coding contained on the tag can not be retrieved without killing the fish, and lethal sampling was not approved during the 1996-2001 monitoring period. Stocking Stocking ofbonytail raised at Wahweap State Fish Hatchery in the Colorado River occurred between October 18, 1996 and April 2001. Stocking in the lower Green River commenced October 27, 1998 and ended in April 2001. Marked bonytail were removed from grow-out ponds at Wahweap, loaded into transport trucks, and delivered to the release sites. The transport water contained 0.5% salt to reduce stress. River water, which was generally cooler, was pumped into the holding tanks to lower temperatures and acclimate fIsh for approximately one hour. The difference in transport and river temperatures was usually 50 C or less. During the first two years of stocking, fish were released in the fall following one season in grow-out ponds. In 1997, the smaller (80-100 mm) portion of that years cohort was held over winter to allow for additional 4