San Francisco Bay has lost more than 90% of historic tidal wetlands and the remaining habitats have been further degraded by contamination, freshwater diversions, and species invasions, among others. The San Francisco Bay Living Shorelines Project at Giant Marsh is a restoration effort intended to provide foraging and habitat resources for a variety of species, with a focus on the enhancement of key native foundational species such as Olympia oysters (Ostrea lurida) and eelgrass (Zostera marina). The project, managed by local, state, and federal partners, comprises 368 acres of existing tidal marsh, oyster reefs, mudflats, and eelgrass beds located within the Point Pinole Regional Shoreline in Richmond, California.
To assess project benefits for the fish community, FISHBIO conducted fish community monitoring using a suite of complementary sampling gears. The goal of this monitoring effort was to understand the fish community that is occupying the newly restored eelgrass plantings and oyster reefs and how this community differs from nearby unrestored areas. Fish data were collected using Adaptive Resolution Imaging Sonar (ARIS) technology, traditional nets, and eDNA to provide information on relative abundance, distribution, species assemblage, and habitat use of fish in restored and unrestored habitats in and around the Project site at the Point Pinole Regional Shoreline.
Oyster beds at low tide.
Fish sampling using seine nets, hoop nets, eDNA, and ARIS monitoring suggested that species composition, size composition, and relative abundance of the fish community was generally consistent across both the restored and existing habitats. This outcome is likely due to the relatively short time since project completion and because fish assemblages readily mix in the dynamic, open intertidal zone. A total of 11 species of fish representing 11 distinct families were captured in the seine and hoop net sampling. Significantly more fish were observed with the ARIS compared to traditional net sampling, and the detection of much larger individuals in the ARIS footage compared to the traditional sampling gears suggested that the hoop and seine nets were less effective at sampling larger fish. eDNA sampling revealed a total of 82 unique sequences belonging to 17 different fish taxa, six of which were not represented in the seine or hoop net catch, indicating that eDNA is a useful tool for capturing species that may evade traditional sampling gear.
Long-term monitoring is a vital component of any management or restoration project, and this monitoring effort suggests that a multi-gear approach may be best suited for assessing fish communities and habitat use in dynamic intertidal areas that are notoriously difficult to sample. Continued monitoring at longer time scales post-restoration is likely needed to assess the effectiveness of these kinds of restoration efforts for the overall fish community.
Header image: Pacific staghorn sculpins (Leptocottus armatus).