|
|
 |
|
|
| |
Communication at the NABS Annual meeting, Keystone, 2000
(377) THE INFLUENCE OF CURRENT VELOCITY AND RESOURCE AVAILABILITY ON FORAGING AND MOVEMENT IN A FILTERING CADDISFLY, BRACHYCENTRUS AMERICANUS.
J.B. Monroe, N.L. Poff, and T. Wellnitz. Department of Biology, Colorado State University, Ft. Collins, CO 80523
We studied foraging behavior and movement (i.e., drifting and crawling) in the stream-dwelling caddisfly, Brachycentrus americanus, across a gradient of current velocity and food availability. B. americanus collects food either by passively filtering the water column or by grazing periphyton from stream substrata. We hypothesized that current speed is the primary factor determining the mode of foraging this insect employs and predicted that filtering would predominate at fast current (> 35 cm/s), whereas grazing would predominate at slow current (< 5 cm/s). To test this, we conducted a streambed survey in the upper Colorado River to record the feeding behavior associated with local current velocity (measured at 12 mm spatial resolution) for randomly located B. americanus. In addition, we conducted an experiment in streamside channels to manipulate current velocity and periphytic abundance. In both the survey and the experiment, filtering behavior increased with current velocity whereas movement decreased. Periphytic abundance had little effect on filtering or movement. It was difficult to ascertain the extent to which B. americanus grazed substrata in the experiment; however, it was clear that current was a critical factor regulating movement and filtering in this species.
Presented at 1:00 PM on Wednesday, May 31, 2000 in Life History Characteristics
|
|
|
|
|
|
|
