Friday March 31, 2023

San Francisco Estuary

On a sunny spring day in 2014, two UC Davis PhD candidates in waders pulled a 30-foot seine through Luco Pond (also known as the Potrero Duck Club) in Suisun Marsh. Luco Pond is within the Nurse-Denverton Slough Complex where duck clubs use tidal gates to control water exchange. After 45 minutes of counting diminutive fish, Brian Williamshen and Melissa Riley were excited to tally more than 6,900 sticklebacks, a thorny-backed native fish in the Sacramento-San Joaquin River Delta.

“There was definitely a moment of excitement,” Williamshen says. “But when we were at our 50th fish, and the little spines kept poking us in the fingers, our emotions shifted to like, oh man, we still have hundreds more to go!”

Several months later, Williamshen pulled a seine at Blacklock Marsh, another site in the Nurse-Denverton Slough Complex. Blacklock is a former duck club that was restored to an open tidal marsh with two breaches in 2006. One of the goals of the project was to improve habitat for endangered species like Delta smelt, but instead of finding native fish, Williamshen counted 874 Mississippi silversides, an invasive fish that had flowed in unrestricted with the tides.

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