Ecosystem-level consequences of migratory faunal depletion caused by dams

Shad 2001: A Conference on the Status and Conservation of Shads Worldwide. Baltimore, Maryland USA. 20-23 May, 2001. PDF on file: 6084_Freeman.pdf
By: , and 
Edited by: K.E. Limburg and J.R. Waldman


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Humans have been damming rivers for millennia, and our more ambitious efforts over the past century have arguably altered river ecosystems more extensively than any other anthropogenic activity. Effects of damming on river biota include decimation of migratory fauna (e.g., diadromous and potamodromous fishes and crustaceans), lost fisheries, and imperilment of obligate riverine taxa. Although effects of dams on biota have been widely documented, ecosystem-level consequences of faunal depletion caused by dams are only beginning to be appreciated. We discuss consequences to river ecosystems of altering distributions and abundances of migratory fauna, which often provide trophic subsidies and may strongly influence the structure of local habitats and communities. It is well documented that anadromous fishes can provide a major input of nutrients and energy to freshwater systems when spawning adults return from the sea. Other less-studied taxa that migrate between distinct portions of riverine systems (e.g., acipencerids, catostomids, and prochilodontids) may similarly provide trophic transfers within undammed river systems, in addition to modifying local communities and habitats through feeding and spawning activities. Experimental faunal exclusions have demonstrated strong potential effects of some amphidromous shrimps and potamodromous fishes on benthic organic matter and algal and invertebrate communities. Depletion of these animals above dams is likely to significantly affect ecosystem processes such as primary production and detrital processing. The decline of freshwater mussels isolated by dams from their migratory fish hosts has likely lowered stream productivity, nutrient retention and benthic stability. Greater focus on effects of dams on ecosystem processes, as mediated by faunal change, would improve our ability to assess the costs and benefits of future river management strategies.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Ecosystem-level consequences of migratory faunal depletion caused by dams
Series number 35
Year Published 2003
Language English
Publisher location Bethesda, MD
Contributing office(s) Patuxent Wildlife Research Center
Larger Work Type Book
Larger Work Subtype Other Government Series
Larger Work Title Biodiversity, Status and Conservation of the World?s Shads
First page 255
Last page 266
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