• brown trout;
  • Salmo trutta;
  • recruitment;
  • lake spawning;
  • groundwater influx

Seepage water through a lake bottom and the layering of tight and high-permeable layers in the aquifer produce groundwater under greater pressure than the water column of the lake. This results in under-water springs and seepages. When spawning substrata were available, there was a spatial correlation between the degree of groundwater influx and the redd density of brown trout Salmo trutta. In high density spawning areas with > 100 observed redds ha−1, the mean seepage water influx during spring was c. 1200 ml m−2 min−1 compared to a mean flux of 113 ml m−2 min−1 in low density spawning areas with 5–10 redds ha−1.