Changes in the catchability of yellow perch Perca flavescens in an otter trawl were examined by comparing annual catch per unit effort (CPUE) in Oneida Lake to mark-recapture population estimates over a series of years. Catchability was similar among age groups of adult yellow perch. Annual catchability was similar in 4 of 5 years, but threefold higher in the fifth, presumably due to lower water clarity in that year. Examination of within-season changes in CPUE indicate that other, undetermined environmental factors also affect catchability.