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Communication at the NABS Annual meeting, Keystone, 2000
(11) THE SPATIAL SCALE OF ENERGY FLOW TO STEELHEAD TROUT IN THE SOUTH FORK EEL RIVER WATERSHED.
J.C. Finlay, S. Khandwala, and M.E. Power. Department of Integrative Biology, University of California, Berkeley, Berkeley, California, USA 94720-3140
The spatial extent of food webs that support top predators in streams is largely unknown but such information is essential for basic understanding and management of lotic ecosystems. We used natural variation in algal stable carbon isotope ratios (d13C) to understand the sources of production for juvenile steelhead trout along a gradient in stream size and productivity in the South Fork Eel River watershed of northern California. In small shaded streams (>95 percent canopy cover), terrestrial detritus or invertebrate inputs clearly supported steelhead production. Although herbivorous invertebrates (scrapers and mayflies) were relatively abundant, they played a minor role in supporting fish growth. Increased algal production caused a sharp transition from terrestrial to algal-based food webs in larger streams and rivers that are important habitats for large size classes of juvenile steelhead. Detailed study of the South Fork Eel River food web showed that algal production in shallow pool habitats provided the energy base for fish in all three major habitat types in the river (shallow pools, riffles, and deep pools) during summer baseflow. Together, these results show that the energy base of steelhead trout in stream and river food webs is often strongly linked to production in adjacent terrestrial or aquatic habitats.
Presented at 1:30 PM on Monday, May 29, 2000 in Wanted Dead or Alive: Role of fish in benthic food webs I
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