Aquatic Sciences Meeting, Albuquerque 2001

CS34 Trophic Dynamics

Date: Friday, February 16, 2001, Time: 10:30:00 AM

Location: Mesilla

Finlay, J, C, University of Wisconsin, Center for Limnology, Madison, USA, jcfinlay@facstaff.wisc.edu

Khandwala, S, B, Stillwater Sciences, Berkeley, USA, sapna@stillwatersci.com

Power, M, E, University of California, Department of Integrative Biology, Berkeley, USA, mepower@socrates.berkeley.edu

THE SPATIAL SCALE OF ENERGY FLOW TO STEELHEAD TROUT IN THE SOUTH FORK EEL RIVER WATERSHED

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 (delta13C) 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 carbon sources supported steelhead production even though herbivorous invertebrates were relatively abundant. However, increased algal production caused a sharp transition from terrestrial to algal-based food webs in downstream open canopied streams that are important habitats for larger juvenile steelhead. Detailed study of the Eel River 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). 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.

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Aquatic Sciences Meeting, Albuquerque 2001

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