Interdisciplinary teams of Center scientists are investigating the causes for the decline of salmon and steelhead in Shasta River, historically one of the most productive tributaries in the lower Klamath Basin. A large spring complex (Big Springs Creek) provides the majority of its water, particularly during the summer.

Researchers are developing innovative approaches to restoring and sustainably managing this unique resource for both native fish and for irrigating local ranches and farms.

Though Shasta River provides only 1 percent of the Klamath River’s streamflow, it historically produced 50 percent of the Chinook salmon  -- and it still produces enough fish to support a large proportion of California’s commercial and recreational salmon fishery. Improving freshwater habitat in the Shasta results in disproportionally large benefits for the lower Klamath Basin.

Chiapas (Mexico) and California share many similar challenges regarding the conservation of rivers and streams and the organisms that dwell in them. 

Although fishes in both states are highly diverse, this biodiversity is under multiple threats including effects from cattle grazing, forest fires, dam operations, and climate change.

Collaboration between the El Ocote Biosphere Reserve and the Klamath National Forest began in 1993 in order to provide research expertise and training between the two forests.  Past efforts have documented fish species presence and distribution within the Reserve (2005-2008; Gonzalez-Diaz et al. 2008, Anzueto-Calvo et al. 2013), as well as identified threats to aquatic habitats (2010-2012). 

The University of California, Davis, joined this collaboration in 2013 by providing guidance on extensive water quality sampling and support in continued fish monitoring.  Important water quality parameters (e.g., concentrations of fecal coliform bacteria) were monitored for the first time in 2013. 

Preliminary results suggest that the bacterial content in some surface waters is several 100 times greater than that recommended by Mexican health standards. 

Fishes from several new sites within the reserve were also collected through electrofishing, seining, and gill netting in 2013. 

This information will be used to update management actions within and around the Reserve.  Proposed future efforts include outlining conservation strategies for the Rio La Venta canyon as well as establishing collaborations with other reserves. 

Knowledge of species' spatial distributions is crucial to the identification and prioritization of watersheds in need of restoration.  Coupled with species' status, the presence and or absence of species can indicate biologically diverse vs. depauperate areas. 

Because California inland native fish species have been extensiverly studied (e.g, Moyle 1976, Moyle et al. 1989, Moyle et al. 1995,  Moyle 2002, Moyle et al. 2011, Moyle et al. 2013), changes in species distribution and status can be used as indicators of changes in overall aquatic ecosystem health.  

In this project, we are compiling all available data for California inland native fish species (134) to create current and historical distribution maps using the PISCES database. 

We are also incorporating status scores for most taxon for the years 1976, 2011, and 2013 in order to track changes in species imperilment or preservation.  Because this data is spatially implicit, we will now be able to analyze biodiveristy patterns at multiple scales (statewide, regional, watershed). 

Our goal is to identify areas most likely to protect aquatic biodiveristy into the future as well as areas needing different levels of restoration. 

Future studies will also analyze existing and potential threats to biodiveristy throughout the state, including climate change, dam operations, and extractive landuses. 

The ultimate goal is the prescription of conservation strategies specific to each area.

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.

Tidal wetland restoration success in Suisun Marsh requires science-based decision support from gathering and synthesis of pre-restoration baseline data. It also relies on a mechanistic understanding of the influence of hydrogeomorphology (flow, tidal prism, channel structure) on foodweb dynamics. Long term data from that project suggest that tidal wetlands in Suisun Marsh function as nurseries for recruiting juvenile fish, presumably because juvenile fish can utilize both pelagic and benthic food webs during this critical period of growth and survival. This project study mechanisms for creating favorable rearing conditions for juvenile estuarine and migratory fishes that rely on tidal wetlands for food and refuge during this critical period of growth and survival, especially in drought years when suboptimal conditions occur further upstream in the Delta. By modeling food web responses to hydrologic change, and differential resource use among native and alien juvenile fish, we gain a better understanding of how management scenarios can promote fish recruitment. We employ empirically-derived hydrodynamic modeling in conjunction with stable isotope modeling of aquatic food webs and patterns of juvenile fish foraging and growth. We hypothesize that (1) hydrology influences productivity and food availability in tidal wetlands, (2) juvenile fish foraging and growth varies as a function of food availability, and (3) juvenile fish resource use varies as a function of life stage and life history strategy (benthic vs. pelagic). Understanding how tidal wetland food webs support juvenile fish improve designs of tidal wetland restoration projects aiming to increase food availability to juvenile native fishes.