HR: 11:00h
AN: NB42C-03    [Abstracts]
TI: Factors Controlling the Age Structure of Margaritifera Falcata in Two Northern California Streams
AU: * Howard, J K
EM: jhowie@uclink.berkeley.edu
AF: Confederated Tribes of the Umatilla Indian Reservation, 73239 Confederated Way, Pendleton, OR 97801
AU: Cuffey, K M
EM: kcuffey@socrates.berkeley.edu
AF: University of California, Berkeley, 507 McCone Hall, Berkeley, CA 94720
AB: We investigated the population dynamics of Margaritifera falcata, in two northern California Coast Range rivers, the South Fork Eel and Navarro. Because they are long lived and relatively stationary, mussels provide insight into how environmental variables influence recruitment and mortality. We used fieldwork and an inverse theoretic modeling technique to measure and analyze age structures to identify factors that control population demographics. The analysis indicates there are distinct mortality rates for younger (< 20 years) and older (>20 years) mussels in the South Fork Eel. In addition, the analysis reveals that recruitment and mortality are both related to river hydrology. In particular, M. falcata recruit more successfully during low flow years than during high flow years. In the South Fork Eel River study area, healthy recruitment is occurring in which ~1,100 - 1,800 individuals are added to the population annually. In contrast, there has been little or no recruitment over the past 30 years in the Navarro River. This difference is likely a consequence of two non-mutually exclusive factors: land use history and host fish populations. By investigating the factors that shape local M. falcata population age structures, we obtained an understanding into how environmental variables and history influence mortality and recruitment.
DE: 0400 Biogeosciences
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly