Original paper

Ecological impacts of hydroelectric power production on the River Ticino. Part 2: Effects on the larval development of the dominant benthic macroinvertebrate (Allogamus auricollis, Trichoptera)

Frutiger, Andreas


In Switzerland most major rivers are utilised for hydroelectric power production. As a consequence their temperature regime is severely altered. Because temperature is an ecological key parameter, substantial ecological consequences may be expected. This study was carried out to analyse the effects of such temperature alterations on the growth and development of the dominant benthic insect. Growth and development of Allogamus auricollis (Trichoptera: Limnephilidae) populations from 13 locations along the River Ticino with very different temperature regimes were investigated between March 1999 and August 2001. To separate temperature effects from possible effects of food limitation, a rearing experiment was also conducted. In two laboratory flumes, where excess food was supplied, caddisfly larvae were reared between February and July 2001 under temperature conditions resembling the coldest and the warmest field site, respectively. Whereas larval growth of A. auricollis in the River Ticino appeared to be mostly independent of prevalent temperatures, it seemed to be temperature controlled in the laboratory, suggesting that larval growth and development of field populations may be food-limited. This assumption is supported by the finding that larval dry weight in the flumes was three times higher than in the corresponding field populations at the end of the rearing experiment. In summary, it seems that larval development of A. auricollis is hardly affected by the temperature alterations due to hydroelectric power production. However, it is suspected that the dominance of this caddisfly per se is probably a consequence of the human induced temperature alterations.


thermal effectslarval developmentcontrolling factorsfood limitationintraspecific interactionsadaptationthermal preferenceshatching