Cyclic dynamics of a yellow perch (Perca flavescens) population in an oligotrophic lake: Evidence for the role of intraspecific interactions

Understanding the extent to which repeated oscillations in fish populations are driven by external factors or internal processes within the population is an important challenge. We document cyclic dynamics in a population of yellow perch (Perca flavescens) in oligotrophic Crystal Lake. Since 1981, we have observed three cases of cohort dominance in which two age-classes dominated the population for roughly 5 years. Young-of-the-year (YOY) perch were caught in 1981-1982, 1986-1987, and 1990-1991, whereas few to no YOY were caught during the midyears. The presence of YOY was negatively related to juvenile perch abundance and positively related to adult perch abundance. Mechanisms that may be responsible for these patterns include cannibalism of YOY by either juveniles or adults, potential for reproduction by adults, and competition between YOY and juveniles. YOY were abundant primarily in years when reproductively mature fish were in the lake, suggesting that the repeated oscillations are driven predominantly by pulses of abundant, reproductive, adult perch. As these young perch grow to juveniles, they exclude the possibility of survival by successive cohorts through cannibalistic and competitive interactions. This exclusion occurs until they themselves become reproductively mature and the cycle then repeats. Ultimately, long-term patterns in Crystal Lake suggest that cyclic dynamics are generated by intraspecific interactions.