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Tuesday, June 5, 2007 - 8:30 AM
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Ansiogammarus kygi (Crustacea: Malocostraca: Amphipoda) in a Kamchatkan Tundra River: Life History and Consumption of Salmon Carcasses
Audrey M. Thompson and Jack A. Stanford. Flathead Lake Biological Station, The University of Montana, 32125 Bio Station Lane, Polson, MT 59860-9659
The marine derived biomass from decaying salmon is incorporated into river systems via the individuals and structures of the freshwater foodweb. In brown water rivers of Western Kamchatka, the feedback loop from Pacific salmon carcass to subsequent juvenile productivity is mediated by large ubiquitous populations of benthic amphipods (Anisogammarus kygi). We describe the life cycle of A. kygi on the Utkholok River, and demonstrate how A. kygi scavenging on salmon carcasses contributes to marine biomass movement through the freshwater foodweb.
A. kygi dominate the macrobenthos, comprising more than 88% (SE=0.01, N=7) of invertebrate biomass. Populations are highly mobile within the system, exhibiting upstream migrations of brooding females (23 ind/m3 ± 5) and redistribution during carcass loading. A. kygi was observed feeding on 97% of salmon carcasses examined (N=100), making up 98.8% (SE 0.007) of decomposers with densities up to 3,000 carcass-1. Amphipods are also an important food item for rearing salmonids such as Onchorynchus keta whose spring diet reaches 76.83% (SE 0.05) amphipods. Our results show that the trophic ecology of A. kygi plays a critical role in the foodweb dynamics of brown water rivers in Western Kamchatka.