Bret Harvey, Rod Nakamoto and Jason White are fish biologists in a U.S. Forest Service Research Work Unit at the Redwood Sciences Lab (RSL) entitled, "Cumulative effects of forest management on hillslope processes, fishery resources, and downstream environments". The overall goal of the research group is to gain a better understanding of the physical and biological processes that integrate terrestrial, riparian, and aquatic ecosystems at the watershed and larger scales. The group takes an interdisciplinary approach to study the production and transport of watershed products (water, sediment, woody debris, nutrients, and heat) and their influence on physical and biological resources (such as water supply and fish populations). The group also seeks to better understand how human activities affect valued aquatic resources and to develop tools useful for decision making by resource managers.
One recent focus of this effort has been research on spatially explicit, individual-based models to directly link physical processes to the population dynamics and community structure of lotic fishes. These models can evaluate population level effects of habitat alterations such as changes in suspended sediment and thermal regimes, and are particularly well-suited for analyzing the cumulative effects of multiple factors on populations of special interest. They also hold great promise for the analysis of alternative management scenarios in river networks influenced by dams and diversions. Research on individual-based models at RSL is founded on collaboration with Dr. Steve Railsback. Seven streams in northwestern California provide the current focus of the modeling efforts; these streams offer contrasts in turbidity regime, thermal regime and habitat complexity over a range of drainage areas.
Models directly linking habitat conditions and animal populations of particular interest can also serve to focus research efforts on poorly understood processes or those most likely to have significant consequences for population dynamics. Modeling results have provided motivation for several of our current field and laboratory research efforts to: 1) better understand the effects of suspended sediment on fish feeding success, and 2) measure the effect of habitat conditions (e.g. streamflow, habitat complexity) on the survival and growth of stream fishes.
Finally, in many ecosystems throughout California and worldwide, the success and effects of invasive species can strongly influence the dynamics of valued aquatic resources, and perhaps significantly interact with other influential factors. Our research group is attempting to determine what characteristics of forest ecosystems reduce the probability of successful establishment and minimize the effects of aquatic invasive species. Another key component of our invasive species research is the evaluation of genetic constraints on the invasion process. In collaboration with Dr. Andrew Kinziger at Humboldt State University, we are identifying source populations and populatin bottlenecks for three cyprinid fishes that have become established in the Eel River of northwestern California.
