Abstract

We assessed the biomass and stable-isotope composition (delta C-13 and delta N-15) of consumers (aquatic insects and fish (Cottus gobio)) and potential food sources (detritus, biofilm, seston, algae, and mosses) in channelized and restored streams in Sweden, assessing the hypotheses that restoration enhances detritus storage and detritus-based secondary production. Restored sites stored more detritus than channelized sites, with differences (+5.4% on average) prominent in margins, i.e., the channel area within 1.4 m from the banks. The biomass of other resources was similar between restored and channelized sites. Most common aquatic insects, including several putative detritivores, showed delta C-13 values indicating reliance on aquatic (probably algal) carbon sources. The insectivorous fish Cottus gobio, on the contrary, appeared to be more dependent on terrestrial (detrital) carbon sources. The biomass and mean delta C-13 values of the consumers were similar between restored and channelized sites, suggesting that restoration did not increase net secondary production or the fraction of secondary production based on detritus. We concluded that the increase in detritus storage at restored sites was either insufficient to enhance detritus-based production or the consumers were not limited by the availability of detritus.

Published in

Canadian Journal of Fisheries and Aquatic Sciences
2006, volume: 63, number: 11, pages: 2478-2486
Publisher: NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

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