Fig. 2.

Monthly average echograms from the 38-kHz echo sounder covering the water column (~0–390 m) for 24 h in July 2007–October 2008. The dominant signal (green) and backscattering at shallower depth (<200 m) is dominated by pearlside, while glacier lanternfish dominate below ~250 m (see Fig. 3 for clarification). The boxes indicate the intervals where the concentration (individuals m⁻³) of glacier lanternfish is calculated (see Fig. 7). Arrows in selected echograms indicate the different behavioral patterns. The color scale refers to average volume backscattering (S _v) for each month; dark red illustrates the strongest, and white the weakest backscatter. The S _v-thresholds are set to −50 and −85 dB for the best possible illustration of the SL’s. Black and white bars above echograms depict night and day separated by times for sunrise and sunset for the 15th each month. Time is given as UTC (local standard time −1 h)