Study to Determine Water Amount Needed for Steelhead Fish to Flourish

CITRIS researchers will implant 40 to 50 anadromous steelhead trout with acoustic tags to determine how much water they need in order to thrive.

Pescadero Estuary, located an hour south of San Francisco, is a coastal habitat under intense pressure from several interest groups. The 643 citizens of the nearby town of Pescadero need fresh water to drink. Local farmers need irrigation water to grow crops. The wild denizens of the wetlands, such as the California red-legged frog and the San Francisco garter snake, need the land for their habitat. And the estuary's endangered fish species need specific seasonal water regimens and salinity levels to survive.

In recent years, competition for favored status in the management of Pescadero's water has become increasingly cutthroat, just as it has throughout the state. A growing human population requires more water every year, leaving less for the state's other species, 279 of which are now listed by the California Department of Fish and Game as threatened or endangered.

In order to find ways to conserve and distribute water more efficiently, this study is being conducted to discover just how much water is needed for steelhead trout to live in order to distribute water to other areas in need. As part of this study in Pescadero Estuary, UC Berkeley engineering professor Mark Stacey and his colleagues will be implanting 40 to 50 anadromous steelhead trout with acoustic tags. The fish will be netted and the tags—capsule-shaped, a little over half-an-inch long, and just under a quarter-inch in diameter—will be surgically implanted into the body cavity of the fish, who will then be released back into the waters.

Each tag emits a unique set of ultra-high-frequency sounds that identifies the fish carrying it. The acoustic signals will be tracked by a dozen or so receivers that will be placed on poles or floated on buoys in strategic positions around the estuary. Using triangulation, maps, and models of known habitat characteristics like temperature, salinity, clarity, and oxygen levels, Stacey's group will develop behavioral models of how steelhead respond to various changes such as the release of water from reservoirs upstream and the influx of sea water that comes when the sandbar cutting off the estuary from the open ocean is breached each winter.

For more information on this study, please visit

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