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The South Bay Salt Pond Restoration Project, the largest wetland restoration project in the western United States, is conducting an adaptive management experiment to restore tidal flows to the tidally muted pond A8 complex. The A8 pond complex is a series of interconnected ponds (A8, A7, and A5) located at the interface of the Guadalupe River with Alviso Marsh in Lower South San Francisco Bay that has had a legacy of mercury contamination from cinnabar open-pit mining in the Guadalupe River watershed. As a result, restoration of salt pond habitats in the Alviso Marsh has taken an adaptive management approach whereby the A8 complex was constructed with operable tide gates to facilitate a stepped approach to opening the pond to tidal action. Fish populations, water and sediment were monitored for mercury contamination before and after opening the tide gates and data was used to inform further restoration actions in the A8 complex. However, Central Coast Steelhead Trout, a threatened species inhabit the streams that enter into the Alviso Marsh and the A8 complex, causing management concern for entrainment of outmigration smolts into the A8 complex.

In this study, UC Davis conducted back-pack electrofishing in the streams that enter the Alviso Marsh during the late-fall winter of 2013 and 2014. The primary objective of the electrofishing was to collect Steelhead Trout juveniles prior to outmigration to tag with Passive Integrated Transponder (PIT) tags for detection of outmigration and potential entrainment into the A8 complex. In addition to the capture and tagging of Steelhead Trout, we collected data on water quality and catch of non-target fishes. To detect outmigration Steelhead Trout we installed a RFID stream antennae in the lower reaches of the Guadalupe River and to detect entrainment into the A8 complex we installed RFID antennas on the A8 water control structure. A total of 106 Steelhead Trout were captured during the two years of stream electrofishing, and 104 fish were tagged with half-duplex 12 or 23-mm PIT tags. In the spring of 2014 we detected a total of 6 fish outmigrating passed the stream antennae and one fish was detected at the A8 water control structure, presumably entering the pond, but was not detected again. No fish were detected outmigrating in the spring of 2015.