The June Sucker Chasmistes liorus mictus is a large-bodied catostomid endemic to Utah Lake, Utah. It is a federally listed endangered species, and one component to its recovery is a stocking program with a target of releasing 2.8 million fish averaging 200 mm long. Because size is implicated as a factor in poststocking survival of western native fishes, particularly in the presence of nonnative fishes, over a 4-year period a combination of telemetry and remote sensing was used to demonstrate size-specific poststocking survival of June Sucker in Utah Lake. A total of 88 June Sucker were released with acoustic tags to estimate short-term survival, and remote PIT scanners were deployed to examine longterm survival. Survival of telemetry fish varied from 0.0 to 0.83, with larger fish exhibiting the greatest survival in the final year. Size-specific survival was most evident in the analysis of PIT scanning data in which survival ranged from 2% for fish shorter than 200 mm to 90% for fish stocked at 300 mm. The causes of mortality are unknown, but likely culprits are nonnative fish and piscivorous birds. Both are well documented preying on June Sucker and similar species. Controlling predation may be impractical, but releasing fewer numbers of larger fish presumably will increase or maintain the population and be more cost effective than the current strategy. Overall, conservation and recovery of June Sucker will be a challenging endeavor going forward.