Feeding habits and food resources of filter-feeding trichoptera in a regulated mountain stream

The feeding habits and food resources of the filter-feeding Arctopsyche grandis and Brachycentrus occidentalis were studied in the Blue river, a tributary of the Colorado river. Both species exhibited distinct longitudinal distribution patterns, a well defined species replacement occurring with A. grandis predominating at 2.3 km below the impoundment and concomitant with its decline downstream there was an increase in B. occidentalis. The less than 75 um organic seston fraction was comprised predominantly of diatoms at all sites during most months. The 75-250 um and greater than 250 um seston fractions were predominantly composed of detritus. More than 70 per cent of the diet of B. occidentalis larvae consisted of detritus and diatoms while in A. grandis, more than 80 per cent of the diet consisted of animals, detritus and/or filamentous algae. There are 41 references.