UWL biology professor fishes for facts to save endangered salmon in California

Research team studies how to boost survival during increasingly severe droughts
Uwl Biology Marsh
Ross Vander Vorste, center, an assistant biology professor at the University of Wisconsin-La Crosse, was on a team with researchers from UC Berkeley and California Sea Grant who published a study on how drought pools affect endangered salmon in the Golden State. Vander Vorste He is pictured with UWL students during a research project in the La Crosse River Marsh last fall. (UWL photo)

LA CROSSE, Wis. (WKBT) — A University of Wisconsin-La Crosse assistant biology professor is helping toss a lifeline to endangered salmon in California.
Ross Vander Vorste and researchers from the University of California-Berkeley and the California Sea Grant have studied the effects of increasingly frequent and severe droughts on the salmon.
They have discovered that the future of the vulnerable fish may pivot on pools that serve as drought refuges and could make the difference between life and death for the vulnerable fish.
The research, in turn, could help resource managers protect and restore salmon habitat.
The new study, published in the journal Global Change Biology, tracked nearly 20,000 tagged fish in Sonoma County streams over a seven-year period from 2011-17.
The Russian River watershed is home to a highly endangered population of coho salmon, which nearly collapsed in the early 2000s. A conservation hatchery program and other efforts have helped it rebound.
“We were able to measure survival during this historic drought, which will help us understand how future droughts will impact this population of salmon,” said Vander Vorste, who conducted the analysis for the study as a UC Berkeley postdoctoral researcher in collaboration with California Sea Grant’s Russian River Salmon and Steelhead Monitoring Program.
The California Sea Grant is a collaboration of the National Oceanic and Atmospheric Administration, the state of California and universities across the Golden State. It is intended to create information, products and services to benefit the economy, the environment and the state’s residents.
Climate change is projected to lead to more frequent and severe droughts in California. In the Russian River watershed and elsewhere in coastal California, salmon spend much of their lives in small streams. These streams often dry up in places during hot, dry conditions, leaving pools of water that become disconnected or dry.
Major questions have arisen about the extent that habitat fragmentation during more severe drought threatens salmon survival and how much water is needed to support the salmon population through the dry summer months.
The team’s previous research showed that even a trickle of water through salmon rearing pools can keep salmon alive.
The new study has a larger set of data that spans an extreme drought, providing insight into what habitats can be refuges during extreme conditions and what physical and environmental conditions may influence survival of juvenile salmon.
Even during the most extreme drought years, the study found, summer survival was similar to survival in non-drought years, indicating that many stream pools act as drought refuges.
In other reaches, lack of flowing water trapped salmon in drying pools, killing them in large numbers.
“For the most part, as long as water persisted in pools throughout the summer, salmon were able to survive,” Vander Vorste said. “So even though we saw decreased survival in many pools, there were some places that emerged as refuges.”
Increasing drought conditions will make it harder for the salmon to hang on, said California Sea Grant Extension Specialist Mariska Obedzinski, who heads the salmon monitoring program.
“So it’s really important that some of these pools did maintain conditions that supported survival,” Obedzinski said. “That gives us hope that there is at least some habitat out there that can support these fish during drought.”
California Sea Grant’s Russian River Salmon and Steelhead Monitoring Program works closely with resource managers in the Russian River watershed. It provides data on salmon survival and monitors stream conditions throughout the year, informing stream flow augmentation projects as well as emergency fish rescue operations.
The new study, which emerged from a partnership with the Russian River Coho Water Resources Partnership Program, provides  information that could help resource managers determine the most effective and feasible measures to protect salmon.
“There are limited resources to address stream flow issues, so this study helps focus our attention in certain areas,” Obedzinski said. “There are different strategies for different conditions.”
In addition helping local salmon recovery, the study also addresses broader ecological questions about the role of habitat fragmentation for endangered species.
“Drought is not only going to affect the Russian River, but will also affect streams and rivers up and down the West Coast and around the world,” Vander Vorste said. “Identifying environmental factors that are limiting salmon survival during those periods is an important finding that could have broader implications.”