The quality of release habitat for reared juvenile flounder, Platichthys flesus, with respect to salinity and depth

One prerequisite for a successful stocking programme is the choice of an appropriate release site, which would ensure good growth, survival and recruitment to the local fishery. The influence of different salinity regimes on habitat quality for juvenile flounder, Platichthys flesus (L.), was examined in Danish inshore waters using enclosures to study growth and survival. Three locations were chosen: Virksund (V) - constant low salinity at 10 parts per thousand; Harre Vig (HV) - constant high salinity at 24 parts per thousand; and Hjerk Nor - variable salinity, 0-25 parts per thousand. Fish movement was examined, using a diffusion model, at the first two sites. At HV the fish had unrestricted dispersal opportunity resulting in average individual movement of 45 m day(-1). Fish at V were restricted in dispersal in one direction because of a dam, about which they would concentrate under certain hydrographical conditions. Growth was highest at the locations with stable salinity and mortality highest at the location with variable salinity.