Lake spawning of brown trout related to groundwater influx

Abstract

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 .