Distribution and diel vertical migration of Eurasian perch (Perca fluviatilis L.) during winter

Abstract

The distribution and migration patterns of overwintering perch were studied by hydroacoustics and gill netting in Lake Constance, central Europe. In autumn, perch left the littoral and moved to deeper waters for overwintering. They lived at temperatures below 6°C for about six months. In January, perch were present between the 42 and 69 m depth contours. Their distribution then shifted to increasingly shallower depths by 0.25 m per day, and they returned to the littoral in early May where adults spawned in late May. During winter, perch performed diel vertical migrations, resting on the bottom during day and swimming up to 25 m off the bottom during night. Light was the proximate cause of this regular vertical migration. Perch did not gain an energetic advantage by migrating in a homothermal water column, but they may have gained access to copepods in addition to their main diet of benthic invertebrates. It is hypothesized that predator avoidance is the ultimate cause of diel migration in overwintering perch which avoid piscivorous birds by resting on the bottom during day and avoid burbot by swimming off the bottom during night.