Aquatic Sciences Meeting, Albuquerque 2001

CS34 Trophic Dynamics

Date: Friday, February 16, 2001, Time: 10:15:00 AM

Location: Mesilla

Rumsey, S, M, Oregon State University, Corvallis OR, USA, Scott_Rumsey@usgs.gov

TROPHODYNAMIC MODELLING OF FISH AND ZOOPLANKTON POPULATIONS IN CRATER LAKE, OREGON

Naturally a fishless lake, Crater Lake was stocked with several species of salmonids between 1888 and 1941. Today, reproducing populations of rainbow trout and kokanee salmon persist. The potential role of kokanee in structuring the ecosystem has been highlighted by observations from the Crater Lake Monitoring Program that suggest top-down control of cladoceran population dynamics. Coincident with peak years in kokanee abundance, the abundance of Daphnia pulicaria has dropped precipitiously, while Bosmina longirostris appears to experience competitive release and a compensatory increase in abundance. A trophodynamic model was developed to explore whether kokanee predation is the primary mechanism controlling cladoceran population dynamics in Crater Lake, or if interannual patterns in zooplankton abundance are best described from a bottom-up perspective. Additionally, sensitivity and elasticity analyses were conducted on the model parameters to determine those variables with the greatest potential influence on zooplankton population dynamics, and that may merit further study and quantification.

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Aquatic Sciences Meeting, Albuquerque 2001

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