Grad student Pamela Beitz's yearlong watershed study reveals how rainbow trout have survived in Redwood Creek. (Courtesy photo)
Grad student tracks source of water sustaining wild trout in urban creek
- May 13, 2011
Water is the stuff of life, and master’s student Pamela Beitz loves it. So much in fact, when she created her interdisciplinary major, the focus centered on collecting rainfall and stream flow for a year to learn how they affect rainbow trout living in a stream just 15 minutes from downtown Oakland.
Beitz is focusing her degree in restoration ecology on Redwood Creek in the East Bay Regional Park District’s Redwood Regional Park, where she has been a park ranger for 10 years. In the process, she has sparked new excitement in her thesis adviser, hydrologist Jean Moran, in the interface between geology and biology.
“I’ve discovered how fascinating that interplay is,” Moran said. “She came up with the idea herself; it’s a multifaceted study.”
At first Beitz wanted to create a restoration plan and obtain official approvals. With faculty input, she decided to make her thesis work manageable by limiting her study to the watershed – the terrain where rain runoff contributes to the stream flow and recharges the groundwater.
She discovered how groundwater seeps in and stretches out stream flow through the dry season, cooling and replenishing pools where the wild rainbow trout remain. Beitz is concerned that non-native trees may be impairing that process, and believes it would not be difficult to restore the area to native species. Also, she says, installing wider culverts could decrease silt deposition along the creek bed. Those changes might ensure the creek will continue to provide sufficient pools for the trout year-round, and ample stretches of gravel for spawning.
“These fish are descended from the trout that were used to name the species,” Beitz said. “They are a precious resource and an important investment in the future.”
By looking at the ratio of different isotopes of oxygen in three types of water samples – from the stream, the below-ground water table, and the rain –– it is possible to tease out how much the rainwater and groundwater contribute to the stream flow. Since California goes for months at a time without rain in the summer, the trout Beitz studied often subsist in the dry season in isolated pools along the stream bed, called refugios.
Just above the place where she collected water samples is an area sporting non-native eucalyptus that she would like to restore. The entire region historically had redwoods -- perhaps bigger than the old-growth trees up north. Following clear-cut logging operations, the existing shady redwood forest has been growing in the canyon near Highway 13 for the past 50 years. During that time, lower regions of the creek were twice dammed to create drinking water reservoirs, cutting off these trout’s access to the sea.
However, the native trout population is genetically identical to ocean-going steelhead trout, which spawn each year in freshwater streams. For that reason, she said, the park’s trout population is an important resource – and has every so often been tapped to restock other areas.
Beitz returned to college about three years ago, building upon an undergraduate major in theater, which also had included chemistry and pre-med coursework. Upon receiving her bachelor’s, she gravitated toward work that used her skills in set-building.
“I couldn’t continue working in a black box,” she said about leaving the theater and changing careers. Maintaining park trails and related duties drew upon her carpentry and welding skills.
Now her job may entail anything from making repairs to explaining ecology to visitors.
“I’ve always been drawn to rivers,” she said of her project. “When groundwater starts to interact with surface water, a whole ecosystem is born. There is a whole food chain just inside the sediment that forms the basis of an entire food web, at the physical science and biological science interface.”
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