| Summary: | Significant loss of wetland habitat with the subsequent loss of suitable habitat for juvenile fish in the San Francisco Estuary has led state and federal agencies along with university researchers to unite in the CALFED Bay Delta Program, which has restored several previously non-tidal marshes in the Estuary to various degrees of tidal amplitude. Hypothetically, reference/historical marshes that have not been diked, dredged or filled should yield greater zooplankton densities (a primary source of food for juvenile fish) compared to marshes recently restored to tidal action. This study examines the hypothesis by comparing zooplankton population densities among reference and restored marshes and testing for a correlation between increased zooplankton densities and increased fish densities within the marshes. Zooplankton sampling occurred approximately monthly (not all sites were accessible each month) at two major reference sites (Edith West Reference Marsh and Statelands Reference Marsh) and at six restored sites (Inner McNabney/Shell Marsh, Outer McNabney/Shell Marsh, Waterfront Marsh, Pt. Edith Marsh, Navy Marsh, all in southern Suisun Bay, and Tubbs Island Marsh in San Pablo Bay). Limited zooplankton sampling was also conducted at two additional reference marshes 10 km up the Delta from Suisun Bay (Northern Brown's Island Marsh and Sherman Island Marsh). At each marsh, zooplankton samples were obtained near the entrance of the tidal channel. The hypothesis of higher reference marsh zooplankton densities was rejected for several marshes with tidal pools connected to the tidal channels; these marshes yielded significantly higher zooplankton densities than the reference marshes. Magnitude of the mean differences ranged from 300-1000%. Furthermore, increased zooplankton densities in these restored marshes with connected tidal pools correlated with increased densities of small fishes. However, two restored marshes lacking tidal pools and one marsh with a small tidal pool yielded significantly lower overall ...
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