Effects of water level fluctuations in large lakes on the littoral benthic fish community


Lake level fluctuations, either men made or natural, are one of the major environmental perturbations in any eulittoral community. In outdoor mesocosm experiments, we test changes in the behaviour and the hierarchical order in two littoral benthic dwellers, juvenile burbot and stone loach under decreasing shelter availability, simulated autumn lake level decrease in large lakes. Recent results show, that the two species show a significantly different behaviour when confronted with decreasing shelter availability. Burbot exhibited a distinct hierarchical order with decreasing shelter availability with larger fish being significantly more successful to compete for their preferred shelter compared to smaller conspecifics. Stone loach in contrast did not show any apparent hierarchical order at all and also no size related shelter use. However, both species showed a significant relationship between their ability to compete for their preferred shelter in a group of conspecifics and their somatic growth rate.
In juvenile burbot, a breakdown of the primarily established hierarchical order was found at the end of the experiment when shelter availability continuously increased. Then, the largest fish of a group started to abandon shelter use at progressive rate while the smaller fish did not show this behaviour. The results indicate two entirely different behavioural strategies to deal with dynamic habitat and environmental perturbations in this two species and demonstrates the importance to conduct behavioural studies not only under strictly controlled and temporally stable conditions but under changing environments which reflects in situ conditions in natural ecosystems as close as experimental constrains allow. The ongoing research in this project now focus on the effects of seasonal water level fluctuation not only on the individual specimen but on the entire lake population.

  • Fischer, Philipp - Project head
  • FB Biologie
Further information
Period: 01.07.2001 – 30.06.2004