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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Biogeochemistry 5
SUBSISTENCE FISHING BY HUMANS AS A MAJOR NITROGEN FLUX IN TROPICAL ANDEAN STREAM ECOSYSTEMS
A.S. Flecker1, J.E. Allgeier1, R.O. Hall, Jr.2, P.B. McIntyre1, B.W. Taylor2,3, C.T. Solomon4, and A.J. Ulseth1.1Department of Ecology & Evolutionary Biology, Cornell University, Ithaca, NY, USA 14853, 2Department of Zoology & Physiology, University of Wyoming, Laramie, WY, USA 82071 , 3Center for Limnology, University of Wisconsin, Madison, WI, USA 53706, 4Department of Biological Sciences, Dartmouth College, Hanover, NH, USA 03755
Fisheries biologists have long been interested in tracking the harvest of tropical fishes from the perspective of managing exploited populations. In contrast, little attention has been paid to examining the extent to which human exploitation of fish populations constitutes a major flux of nutrients in tropical streams. During the dry seasons of 2004 and 2005, we constructed nitrogen budgets in Rio Las Marias, a mid-sized stream located in the Andean piedmont of Venezuela, to evaluate whether fishing removed significant amounts of nutrients in this N-limited system. Using roving surveys, we quantified fishing pressure on a dominant detritivore, the flannelmouth characin, Prochilodus mariae, and found considerable variation between consecutive years. In 2004, fishers harvested more than half of the fish in the study reach. The magnitude of this negative flux exceeded estimates of both inputs via N-fixation and net export of suspended particulate and dissolved N forms via fluvial processes. Interestingly, during 2005 the N flux via fishing was inconsequential relative to other fluxes in our study reach. We suggest that the direct effect of harvesting can be an important nutrient flux in many tropical streams, and can have substantial impacts on ecosystem structure and function.
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