Spawning site selection by Eurasian perch (Percafluviatilis L.) in relation to temperature and waveexposure

The selection of spawning depth by Eurasian perch Perca fluviatilis was investigated in an experiment using artificial substrata in Lake Constance during the spawning season of 2007. The experiment compared spawning behaviour at substrata between 0.5 and 15 m depth at two sites exposed to different regimes of ship-generated wave action. The total abundance of egg ribbons did not differ significantly between the two sites, but the preferred spawning depth was deeper at the wave exposed site (5 m) compared to the sheltered site (2 m). While water temperatures could not account for the observations, differences in wave exposure may explain the different spawning depth preferences. At both sites, large egg ribbons were generally found in deeper water, and large egg ribbons occurred more frequently at the sheltered site. Because the egg ribbons of perch are likely to have a size-dependent susceptibility to hydrodynamic stress, large females may be expected to select deeper spawning locations where the effects of surface waves are considerably attenuated. W. N. Probst, S. Stoll, H. Hofmann, P. Fischer, R. Eckmann Limnological Institute, University of Konstanz, Konstanz, Germany, Alfred-Wegener-Institute für Polar and Marine Research, Biologische Anstalt Helgoland, Helgoland, Germany