The two most important Chinook salmon stocks for fisheries in California — the Sacramento River Fall Chinook and the Klamath River Fall Chinook — were designated as overfished in 2018. Assessment errors could have contributed to the decline. Regulatory agencies use forecast models before each season to set harvest levels and to develop long-term management strategies. For Sacramento River Fall Chinook, a preseason overforecast of abundance resulted in overharvesting.

Wetland ecosystems can serve as powerful carbon sinks and play a key role in mitigating climate change. But wetlands can also be a source of carbon. Hydrological carbon export, which occurs when the carbon passes from wetlands into connected oceanic ecosystems, remains understudied, limiting the understanding of wetland carbon cycling. This project refined current models of carbon sequestration rates in tidal wetlands by incorporating new data on the export of dissolved inorganic carbon. 

California’s Central Valley has a strong agricultural economy, but modern farm practices expose both human and ecological communities to various chemical risks. Many farmers are disconnected from the best scientific information about the impacts of the chemicals they use. This project aimed to raise awareness and provide education by updating the Pesticide Management Prioritization Model, which was first developed by Nicol Parker with the support of a 2020 Delta Science Fellowship.

Thousands of acres of land have been restored to tidal marsh in the San Francisco Bay and Delta (Bay-Delta) over the last two decades, often by breaching old dikes. Currently, several more large-scale, multiagency marsh restoration projects are planned or underway. Nevertheless, the extent to which dike breaching yields robust and diverse aquatic food webs remains unclear. 

As California’s climate changes, many communities will need to adapt to new conditions. However, adaptation is challenging, made more so by the complex web of agencies and organizations involved. This complexity can undermine efforts to ensure adaptation strategies are applied equitably.

PROJECT HIGHLIGHT:

This project analyzed decades of monitoring data to understand how freshwater flows affect longfin smelt across different habitats in the San Francisco Estuary, revealing that while increased flows generally benefit smelt populations, this effect has weakened over time in some areas as the threatened species potentially adapts by shifting habitats.

PROJECT SUMMARY:

Several invasive pests, including red swamp crayfish, American bullfrogs and nutria rodents, can now be found in the Sacramento-San Joaquin River Delta. At the same time, native snakes that feed on these species are struggling. Some are classified as threatened and their populations are continuing to decline, making further study of their behaviors essential. This project investigated the relative abundance, habitat use and diet of snakes at two sites in the Delta, Staten Island Preserve and a wetland in Clarksburg privately owned by Tom and Laura Uslan.

Cyanobacterial Harmful Algal Blooms (cyanoHABS) occur when water conditions foster the growth of algal species that can produce toxins. Recently, there have been more algae in blooms in the Sacramento-San Joaquin Delta, as well as more varied cyanoHABS. Scientists don’t yet know what is causing the expanded blooms or how the increased diversity will impact the spread of toxins.