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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 fish populations, water and sediment were monitored for mercury contamination before and after restoration actions and data was used to inform further restoration actions in the A8 complex.

In this study, UC Davis conducted fish sampling to collect 2-sentinel species, the Three-spine Stickleback and Mississippi Silverside to assess whole-body mercury concentrations. Fish were collected seasonally (4-5 surveys-year) from spring 2014 through winter 2017 at two slough locations exchanging water with the A8 complex, one in upper Alviso Slough (ALSL-2) at the Alviso Municipal Marina boat launch and on in lower Alviso Slough (ALSL-3) near the pond A7 water control structure, and in two reference sloughs, Artesian/Mallard Slough just downstream from the San Jose-Santa Clara Regional Wastewater Facility outfall and Guadalupe Slough at the confluence with the Sunnyvale Wastewater Treatment Plant. Fish sampling consisted of beach seine, minnow trap and fyke netting with various levels of effort to capture the requisite number and size of sentinel fishes. Therefore, much of the sampling efforts were not conducted in a manor conducive of making fish abundance or species assemblage comparisons amongst the sampling locations.

In addition to the slough sampling, we sampled for fish in tidal muted ponds A8, A7, A5, A3N, A3W and A16 from spring 2014 through winter of 2016 and added sampling in tidal restored ponds A6, A17, A19, A20 and A21 from summer 2015 through spring 2016 to facilitate comparisons of species assemblage among tidal sloughs, tidal restored ponds and tidal-muted/managed ponds.