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  • Elwha River salmon carcass addition experiment


Northwest Fisheries Science Center (NWFSC) Fish Ecology FE - Watershed


Elwha Salmon Carcass 2007
Elwha River salmon carcass addition experiment
Dam removal and other fish-barrier removal projects in western North America are assumed to boost freshwater productivity via the transport of marine-derived nutrients from recolonizing Pacific salmon (Oncorhynchus spp). In anticipation of the removal of two hydroelectric dams on the Elwha River in Washington State, we tested this hypothesis with a salmon carcass addition experiment. Our study was designed to examine how background nutrient dynamics and benthic foodwebs vary seasonally, and how these features respond to salmon subsidies. We conducted our experiment in six side channels of the Elwha River, each with a spatially paired reference and treatment reach. Each reach was sampled on multiple occasions from October 2007 to August 2008, before and after carcass placement. We evaluated nutrient limitation status, measured water chemistry, periphyton, benthic invertebrates, and juvenile rainbow trout (O. mykiss) response, and traced salmon-derived nutrient uptake using stable isotopes. Outside of winter, algal accrual was limited by both nitrogen and phosphorous and remained so even in the presence of salmon carcasses. One month after salmon addition, dissolved inorganic nitrogen levels doubled in treatment reaches. Two months after addition, benthic algal accrual was significantly elevated. We detected no changes in invertebrate or fish metrics, with the exception of 15N enrichment. Natural seasonal variability was greater than salmon effects for the majority of our response metrics. Yet seasonality and synchronicity of nutrient supply and demand are often overlooked in nutrient enhancement studies. Timing and magnitude of salmon-derived nitrogen uptake suggest that uptake of dissolved nutrients were favored over direct consumption of carcasses. The highest proportion of salmon-derived nitrogen was incorporated by herbivores (18–30%) and peaked 1–2 months after carcass addition. Peak nitrogen enrichment in predators (11–16%) occurred 2–3 months after addition. All taxa returned to background d15N levels by 7 months. Since this study was conducted, both dams on the Elwha River were removed over 2011-2014 to open over 90% of the basin to anadromous fishes. We anticipate that as the full portfolio of salmon species expand through the basin, nutrient supply and demand will become more balanced and positive feedback loops of reciprocal nutrient transfer reinforced.

Research Themes

Habitats to support sustainable fisheries and recovered populations
Healthy oceans, coastal waters, and riverine habitats provide the foundation for aquatic resources used by a diversity of species and society. Protecting marine, estuarine and freshwater ecosystems that support these species relies on science to link habitat condition/processes and the biological effects of restoration actions. The NWFSC provides the habitat science behind many management actions taken by NOAA Fisheries and other natural resource agencies to protect and recover aquatic ecosystems and living marine resources. The NWFSC also maintains a longstanding focus on toxic chemical contaminants, as a foundation for regional and national research on pollution threats to fisheries and protected resources.

Research Foci

Develop effective and efficient habitat restoration and conservation techniques
Maintaining and re-establishing viability and sustainability of living marine resources requires conservation and rehabilitation or restoration of habitats upon which species depend. Common habitat restoration approaches and tech-niques often presume that habitats are static features of the environment, and that creation of stable habitats is a desirable restoration strategy. However, riverine, nearshore, and marine habitats are created and sustained by dynamic landscape, climatic, and oceanographic processes and biota are adapted to changing habitats that are within the range of natural variability. Hence, current restoration strategies often have limited success, in part because they fail to recognize larger scale processes that drive habitat change, and in part because they fail to recognize intrinsic habitat potential of individual restoration sites. The main goals of this research focus are to: improve understanding of how large-scale processes create diverse and dynamic habitats that support marine and anadromous species, better understand how human activities alter habitat-forming processes and habitats, develop new restoration techniques that are compatible with sustainable habitat-forming processes, and understand the variety of actions needed to adequately conserve intact critical habitats. In addition, NWFSC’s research will improve understanding of how new and existing habitat restoration and protection techniques affect fish and habitat at multiple scales (i.e., reach, watershed, Evolutionarily Significant Unit).


Elwha River
river located on the Olympic Peninsula of Washington State
aquatic invertebrate
animals without backbones that live some portion of their life cycle in the water
dam removal
related to removal of dams from rivers
effectiveness monitoring
evaluating whether actions had desired effects on physical, chemical, or biological processes
flat depositional feature of a river valley adjoining the channel
food web
complex of interrelated food chains in an ecological community
related to fish habitat (terrestrial or marine)
marine derived nutrients
nutrient originating from marine sources
nutrient enrichment
addition or organic or inorganic compounds to a water body to increase background levels of nutrients
layer of biofilm covering the benthos
all salmonids
side channel
subsidiary or overflow channel branching from the primary river channel
stable isotopes
isotopes of an element that have the same atomic number, but different atomic mass


Effects of salmon carcasses on riverine food webs in experimental field study on the Elwha River
Talk given at 81st Annual Meeting of the Northwest Scientific Association, Seattle, WA
Transfer of marine-derived salmon nutrients to freshwater food webs: predicted response of primary and secondary producers to dam removal on the Elwha River (Washington state), USA
Talk given at the 5th World Fisheries Congress, Yokohoma, Japan


Class Arachnida
Class Insecta
Phylum Annelida
segmented worms
Phylum Bacillariophyta
Phylum Mollusca
Phylum Platyhelminthes
flatworms, platyhelminths
Species Oncorhynchus kisutch
Coho salmon, silver salmon
Species Oncorhynchus mykiss
rainbow trout, steelhead trout, syeelhead trout


Beth Sanderson
Sarah Morley
Principal Investigator