PARENT SESSION
Oral Session #29: Invasions: Predicting and understanding invasibility. Presiding: K. Kearns.
Tuesday, August 7, 2001. 1:00 PM to 4:45 PM. Madison Ballroom C.
Understanding fish invasions in California: patterns in humans and watersheds.
Marchetti, Michael1, Moyle, Peter2, Light, Theo2, Feliciano, Joaquin2, 1 2
ABSTRACT- California's freshwater fish have exhibited decline over the last century. This coincides with spectacular changes to the natural landscape and dramatic increases in non-native fishes. Based on our observations of California's freshwater fish fauna, we believe that changes in the composition of fish assemblages across the state and the alteration of aquatic habitats are strongly linked. To examine this we combined watershed specific data on historic and present fish assemblages with geographic data on land use, development patterns and natural environmental features. We investigated questions of whether watershed characteristics (natural and anthropogenic) are related to changes in the freshwater fish assemblages in California, using multiple regression and community ordination techniques. Our results indicate the following: 1. introduced species are positively associated with watershed characteristics indicating anthropogenic change (number of dams, density of aqueducts and ditches and proportion of watershed area developed); 2. species extinctions are positively associated with aqueduct density and the proportion of watershed area in agriculture, (also indicating anthropogenic change); 3. native species are positively associated with natural environmental characteristics (mean rainfall, stream densisity and mean elevation). The results suggest there are strongly negative effects on aquatic biological diversity from the landscape level changes we are making to the freshwater systems of California.
KEY WORDS: invasive species, California, biodiversity, anthropogenic change