How do river ecosystems support fish? How do environmental changes influence the system’s capacity to support fish? And how might different restoration strategies influence fish? These are questions J. Ryan Bellmore, a research fish biologist who works in Juneau, Alaska, for the USDA Forest Service’s Pacific Northwest Research Station, and his partners set out to answer.
River restoration is typically aimed at recovering or conserving one or two target species like salmon or trout. It also influences all the other river species and the larger food web—the natural interconnection of many food chains made up of animals and plants that connect in many ways.
“To successfully conserve and restore one species, we need to know how the larger food web responds to our efforts,” said Bellmore. Bellmore and his partners recently published a report describing a model that can help address specific river research and management questions.
This model—the Aquatic Trophic Productivity (ATP) computer simulation—is an interactive tool that links the success of fish populations to the food webs and the conditions that influence them. The model separates aquatic organisms into “trophic groups” that share similar predators and prey. These relationships are then linked to the physical and chemical conditions of the river, including the movement of the water and the structure and composition of vegetation along the river’s edge.
The model can be used to predict responses to management actions like reconnecting natural floodplains, restoring the vegetation along the river, and increasing water nutrients. It can also be used to evaluate longer-term environmental changes in the climate, water temperature and stream flow.
Bellmore began to build models of rivers while he was a postdoctoral researcher with the U.S. Geological Survey. There he worked to determine the effects of river restoration efforts on salmon recovery in the Columbia River, where many populations are threatened or endangered.
“The model is flexible,” Bellmore said. “It can be adjusted to explore a range of research questions.”
Recently, the ATP model was used to explore food web and fish responses to dam removal and floodplain restoration on rivers in Washington state. The model is currently being used to explore how climate change will impact the capacity for Alaskan rivers to continue to support abundant salmon populations in the future.