PRECISION OF AGES DETERMINED FROM SCALES AND OPERCLES FOR YELLOW PERCH PERCA-FLAVESCENS

Scales and opercles were used to age yellow perch Perca flavescens col lected in 1989 from Lake Madison (South Dakota), Dauphin Lake (Manitob a), and southern Lake Michigan (Indiana). Three readers aged fish from Lake Madison and Dauphin Lake once and two readers aged fish from Lak e Michigan twice. The coefficient of variation (CV;) was calculated to compare precision. Ages determined from opercles were as precise as t hose from scales for fish from Lake Madison (CV = 0 for both structure s), and more precise than ages from scales for fish front Dauphin Lake (CVopercle = 14,0 CVscale = 27.4, p < 0.001) and Lake Michigan (CVope rcle = 10.6, CVscale = 13.9, p < 0.001). The high precision of scale a nd opercle ages for yellow, perch from Lake Madison can be attributed to the fast growth rare of fish from that lake and also that only age I and 2 fish were aged. The greater precision of opercle ages in compa rison to scale ages for Dauphin Lake and Lake Michigan yellow perch sa n be attributed to ease of recognition of false annuli on opercles as well as to difficulty in distinguishing between false and true annuli crowded on the edge of scales from mature, slower growing fish. Becaus e tale annuli ale more easily recognized on opercles, ages determined from opercles may be more accurate than ages determined from scales fo r yellow perch growing at slow or moderate rates.