Ecosystem Modeling of Becharof Lake, a Sockeye Salmon Nursery Lake in Southwestern Alaska

Ecosystem Modeling of Becharof Lake, a Sockeye Salmon Nursery Lake in Southwestern Alaska

Ole A. Mathisen and Norma Jean Sands

Ecosystem Modeling of Becharof Lake, a Sockeye Salmon Nursery Lake in Southwestern AlaskaThis is part of Ecosystem Approaches for Fisheries Management
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Description

Ecosystem management is dependent on knowledge of species interrelationships within an ecosystem. For sockeye salmon (Oncorhynchus nerka) nursery lakes such as Becharof Lake in southwestern Alaska, we are interested in the food competitors, predators, and prey of the juvenile sockeye salmon. Two methods were used to examine the structure of the ecosystem and determine trophic levels of species groups: (1) the use of marinederived nitrogen levels in organisms determined from stable isotope ratios, and (2) the use of an ecosystem model based on biomass, production, and consumption estimates of each species group. In spite of the many assumptions needed to develop the ecosystem model, the two methods gave similar estimates of trophic level per species group. The development of the ecosystem models helps identify what data are available for the system under study and what data are needed to improve understanding of the system.

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