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. RMA2 models will be implemented with particle tracking functionality based upon continuous monitoring, and will be used to try to capture monthly sample variability (King and Norton 1978, King 1988). Spatial and statistical modeling will be implemented in ArcGIS and Program R (R Development Core Team 2015), using maximum likelihood and information theoretic approaches to select appropriate descriptive models (Bolker 2008, McElreath 2016) to address the following hypotheses:

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.

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