Abstract


QUANTIFYING THE EMERGENCE OF GIANT STONEFLY (PTERONARCYS CALIFORNICA) AND ITS IMPORTANCE TO TERRESTRIAL FOODWEBS IN THE U.S. WESTERN RIVERS

Giant stoneflies (a.k.a. salmonflies) are iconic insects of Western U.S. rivers. They are large-bodied, can occur at very high densities, and are important prey for fishes and terrestrial predators. We quantified the magnitude of their emergence (abundance and carbon flux) in medium-to-large rivers in Colorado. We measured abundance using multi-pass depletion of exuvia, and reared late-instar larvae in the laboratory to develop ash-free dry mass (AFDM) relationships between exuvia and adults. Abundance varied considerably within and among riffles, but this variation was small compared to among-river differences (e.g., 25-567 exuvia/m shoreline in 2013). Females were two-fold larger than males, and individual masses varied two-fold among rivers (female range = 175-300 mg AFDM). Salmonflies exported 156 g C/m shoreline/y at the most abundant site (Colorado River) in 2013, 10-fold higher than predicted for annual C flux of all insect taxa for a similarly sized river. Carbon fluxes by salmonfly emergence at other sites also commonly met or exceeded this annual prediction. Thus, synoptic emergence of large, productive taxa is a potentially significant carbon source for riparian foodwebs, particularly in semi-arid landscapes.

Authors

Walters, D. M., US Geological Survey, USA, waltersd@usgs.gov

Zuellig, R. E., US Geological Survey, USA, rzuellig@usgs.gov

Kowalski, D. A., Colorado Parks and Wildlife, dan.kowalski@state.co.us

Wesner, J. S., University of South Dakota, Jeff.Wesner@usd.edu

Details

Oral presentation

Session #:050
Date: 5/20/2014
Time: 14:15
Location: B 115

Presentation is given by student: No