The population dynamics of pike, Esox lucius, and perch, Perca fluviatilis, in a simple predator-prey system

The population dynamics and predator-prey relationship of pike, Esox lucius , and perch, Perca fluviatilis , were examined in simple fish communities in two adjacent shallow lakes, Lochs Kinord and Davan, Deeside, Scotland. Few perch survive to age 3 but Z is low for fish > 3 years and perch live up to 17 years. Population fecundity remained relatively high and constant in perch because of the muti-age spawning stock and the presence of older more fecund perch. Growth rates of perch in both lochs are relatively high as a consequence of low stock abundance. There was little variation in the strength of pike years classes and the importance of cannibalism and low occurrence of alternative prey in the lochs suggest that the populations were self-regulating. Cannibalism by adults was responsible for most of mortality in perch larvae, and predation by pike and adult perch was responsible for the majority of juvenile losses.