Short-term cues used by foraging trout in a California stream |
| |
Authors: | Charles Gowan |
| |
Institution: | (1) Department of Biology, Randolph-Macon College, Ashland, VA 23005, USA |
| |
Abstract: | Stream salmonids choose foraging locations to maximize the energy benefit of foraging within the constraints of size-mediated
dominance hierarchies and predation risk. But, because stream habitats are temporally variable, fish must use a search process
to monitor changing habitat conditions as a means of locating potentially-better foraging locations. I explored the cues used
by the cutthroat trout, Oncorhynchus clarki clarki, when searching for food at the pool scale by artificially increasing prey availability at different locations by using special
feeders and by manipulating pool velocities. Behavior of individually marked fish was monitored from stream bank platforms
under unmanipulated control conditions and under seven experimental sets of conditions involving different combinations of
feeder location and velocity manipulation. Under natural conditions fish elected to forage in the deepest (>50 cm), fastest
(0.10–0.25 m s−1) locations and within 1 m of structure cover, but would readily move to shallower (<30 cm) water away from cover if velocities
were manipulated to be highest there. Although fish did not locate feeders unless they were placed in high-velocity areas,
when high velocity was provided fish would move into very shallow water (<20 cm) if prey were delivered there. Responses of
individual trout to manipulations indicated that water velocity was the main physical cue used by fish to decide where to
forage, and that fish could also learn about new food sources by observing conspecifics. Overall, results indicated fish were
not “perfect searchers” that could quickly locate new food resources over short time scales, even when the new resources were
within a few meters of the fish’s normal foraging location. When given the correct cues, however, fish could detect new food
sources and defend them against subordinate fish. Movement of new fish into and out of the study pools during the ten-day
observation period was common, consistent with the idea that trout used movement as a means of exploring and learning about
habitat conditions at the reach scale. |
| |
Keywords: | Oncorhynchus clarki clarki Drift feeding Habitat selection Optimum foraging Learning |
本文献已被 SpringerLink 等数据库收录! |
|