Goldstein, Allyson: Harvey, Chris J and Peter M. Kareiva. "Community Context and the Influence of Non-Indigenous Species on Juvenile Salmon Survival in a Columbia River Reservoir." Biological Invasion 7 (2005): 651-663.
Summary:
Harvey and Kareiva use a mathematical model to determine how removing non-indigenous species from the John Day Reservoir on the Columbia River would affect Chinook salmon and steelhead. Many scientists claim that non-indigenous species are the second greatest threat to endangered species after habitat loss. While scientists have conducted many studies about the effects of dams and habitat loss on salmon, very few have focused on the impact of the four non-indigenous predator fish in the Columbia River.
Using existing data about the rates at which both indigenous and non-indigenous predators eat smolts, Harvey and Kareiva calculate how the removal of different species would affect salmon populations. According to their calculations, non-indigenous species have a surprisingly modest effect on projected salmon populations. In fact, with the removal of certain invasive species, the mathematical model actually predicts a decrease in smolt population because other predators would increase in biomass. In addition, the study finds that reducing natural predators that are overabundant because of human impacts on the river would lessen damage to smolt populations each year. The authors conclude, however, that the removal of non-native species would have a positive effect on the overall salmon and steelhead populations.
Critique:
The study provides a good framework for examining the impacts of non-indigenous species on salmon and steelhead populations, but given the infinitely complex nature of the food web, it may not present the whole picture on the relationships between different species in the Columbia River. Furthermore, because the study only looked at one reservoir along the Columbia River, it may not accurately reflect the situation along the whole river. Despite these shortcomings, the study offers a mathematically derived look at how individual non-indigenous species and combinations of non-indigenous species and natural predators affect salmon populations in the Columbia River that would be impossible to generate with raw observational data from the river. The study does not go so far as to say that all non-indigenous fish species should be removed from the river, but does leave it an open-ended possibility without addressing the practical and financial aspects of such a project.
(reviewed by Allyson Goldstein)
Robert D. Clark Honors College, University of Oregon
HC 441: Science Colloquium, Columbia River Ecology
Fall term, 2005
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