Arc of Native Fishes

This project aims to provide a better understanding of how land and vegetation in the Sacramento-San Joaquin Delta interact with river flow and tides to create habitat favored by native fishes. The investigation focuses on regions in the north Delta where fish surveys have shown relatively high populations of native fishes - regions including Suisun Marsh, the flooded Sherman Island and the Cache and Lindsey sloughs. The areas together form an arc, inspiring the project name "North Delta Arc of Native Fishes."





This study is a unique examination of how local, regional and broad-scale environmental conditions influence fish recruitment, rearing, and reproduction in diverse habitats, including restored wetlands. It will produce essential background information needed to inform how well tidal marsh restoration projects work to support native fish populations in the CLC. We employ an interdisciplinary approach that couples hydrodynamic and particle tracking models with empirical data on distribution and abundance of phytoplankton, zooplankton, epibenthic invertebrates, and juvenile and adult fishes across habitat types. Monthly and continuous data on water quality and flows will be used to inform a developing regional hydrodynamic model which will be implemented. The model will characterize spatial and temporal changes in water quality due to tidal cycles, local inputs and exports. Monthly cruises will collect additional data on water quality, nutrients and chlorophyll-a. Zooplankton and epibenthic invertebrate are sampled by plankton and otter trawls. Fish are sampled using otter trawling, beach seining, and boat electrofishing. All data are collected concurrently to assess prey availability across species’ life histories. Analysis includes hydrodynamic, spatial and statistical approaches.

We are interested in learning how:

1. Increased overland flow and Delta outflow (from precipitation) pushes environmental conditions to favor certain native and pelagic species in the north Delta.

2. Hydrodynamic variability, including spring/neap tide cycles and overland flow, creates conditions that support biomass accumulation and periodic export in terminal sloughs, causing episodic “pulses” of increased food availability to pelagic organisms.

3. Timing of food pulses affects the community composition of fishes by favoring species that are recruiting concurrently with food pulses.

4. Differences in the fish community composition of sloughs is driven by species’ phenology and food web structure.

5. Restoration outcomes for pelagic fishes depend upon the influence of hydrodynamic and geomorphic characteristics on food webs.

For data, contact

Project Contact: