scholarly journals Physical Characteristics Influencing Nearshore Habitat Use by Juvenile Chinook Salmon in the Sacramento River, California

2018 ◽  
Vol 38 (4) ◽  
pp. 959-970 ◽  
Author(s):  
Michael Hellmair ◽  
Matthew Peterson ◽  
Brian Mulvey ◽  
Kip Young ◽  
John Montgomery ◽  
...  
Keyword(s):  
Habitat Use ◽  
Chinook Salmon ◽  
Physical Characteristics ◽  
Sacramento River ◽  
Juvenile Chinook Salmon ◽  
Juvenile Chinook ◽  
Nearshore Habitat

scholarly journals Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

2020 ◽  
Author(s):  
Eric J. Holmes ◽  
Parsa Saffarinia ◽  
Andrew L. Rypel ◽  
Miranda N. Bell-Tilcock ◽  
Jacob V. Katz ◽  
...  
Keyword(s):  
Growth Rates ◽  
Chinook Salmon ◽  
Rice Fields ◽  
Sacramento River ◽  
Fish Conservation ◽  
Juvenile Chinook Salmon ◽  
Flooded Rice ◽  
Avian Predators ◽  
Juvenile Chinook ◽  
Field Drainage

AbstractThe rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as promising habitat for rearing juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods for rearing fall-run Chinook Salmon on winter-flooded rice fields in the Yolo Bypass, a modified floodplain of the Sacramento River in California. These included: 1) influence of field substrate differences from previous season rice harvest; 2) effects of depth refugia from avian predators (trenches); 3) field drainage methods to promote efficient egress of fish; and 4) in-field salmon survivorship over time. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant when directly compared to the adjacent Sacramento River. Correspondingly, somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater versus fish in the adjacent Sacramento River. Post-harvest field substrate treatments had little effect on the lower trophic food web and had an insignificant effect on growth rates of in-field salmon. Though depth refugia did not directly increase survival, it buffered maximum water temperatures in the trenches and facilitated outmigration from fields during draining. Rapid field drainage methods yielded the highest survival and were preferable to drawn-out drainage methods. High initial mortality immediately after stocking was observed in the survival over time experiment with stable and high survival after the first week. In-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. The abundance of food resources and exceptionally high growth rates observed during these experiments illustrate the benefits associated with reconciling off-season agricultural land use with fish conservation practices. Without any detriment to flood control or agricultural yield, there is great promise for reconciliation ecology between agricultural floodplains and endangered fish conservation where minor alterations to farm management practices could greatly enhance the effectiveness of fish conservation outcomes.

scholarly journals Reconciling fish and farms: Methods for managing California rice fields as salmon habitat

2020 ◽  
Author(s):  
Eric J. Holmes ◽  
Parsa Saffarinia ◽  
Andrew L. Rypel ◽  
Miranda N. Bell-Tilcock ◽  
Jacob V. Katz ◽  
...  
Keyword(s):  
Growth Rates ◽  
Chinook Salmon ◽  
Rice Fields ◽  
Sacramento River ◽  
Fish Conservation ◽  
Juvenile Chinook Salmon ◽  
Flooded Rice ◽  
Avian Predators ◽  
Juvenile Chinook ◽  
Field Drainage

AbstractThe rearing habitat for juvenile Chinook Salmon (Oncorhynchus tshawytscha) in California, the southernmost portion of their range, has drastically declined throughout the past century. Recently, through cooperative agreements with diverse stakeholders, winter-flooded agricultural rice fields in California’s Central Valley have emerged as promising habitat for rearing juvenile Chinook Salmon. From 2013 to 2016, we conducted a series of experiments examining methods for rearing fall-run Chinook Salmon on winter-flooded rice fields in the Yolo Bypass, a modified floodplain of the Sacramento River in California. These included: 1) influence of field substrate differences from previous season rice harvest; 2) effects of depth refugia from avian predators (trenches); 3) field drainage methods to promote efficient egress of fish; and 4) in-field salmon survivorship over time. Zooplankton (fish food) in the winter-flooded rice fields were 53-150x more abundant when directly compared to the adjacent Sacramento River. Correspondingly, somatic growth rates of juvenile hatchery-sourced fall-run Chinook Salmon stocked in rice fields were two to five times greater versus fish in the adjacent Sacramento River. Post-harvest field substrate treatments had little effect on the lower trophic food web and had an insignificant effect on growth rates of in-field salmon. Though depth refugia did not directly increase survival, it buffered maximum water temperatures in the trenches and facilitated outmigration from fields during draining. Rapid field drainage methods yielded the highest survival and were preferable to drawn-out drainage methods. High initial mortality immediately after stocking was observed in the survival over time experiment with stable and high survival after the first week. In-field survival ranged 7.4–61.6% and increased over the course of the experiments. Despite coinciding with the most extreme drought in California’s recorded history, which elevated water temperatures and reduced the regional extent of adjacent flooded habitats which concentrated avian predators, the adaptive research framework enabled incremental improvements in design to increase survival. The abundance of food resources and exceptionally high growth rates observed during these experiments illustrate the benefits associated with reconciling off-season agricultural land use with fish conservation practices. Without any detriment to flood control or agricultural yield, there is great promise for reconciliation ecology between agricultural floodplains and endangered fish conservation where minor alterations to farm management practices could greatly enhance the effectiveness of fish conservation outcomes.

scholarly journals Detrital Food Web Drives Aquatic Ecosystem Productivity in a Managed Floodplain

2019 ◽  
Author(s):  
Carson A. Jeffres ◽  
Eric J. Holmes ◽  
Ted R. Sommer ◽  
Jacob V.E. Katz
Keyword(s):  
Food Web ◽  
Chinook Salmon ◽  
Carbon Sources ◽  
River Channel ◽  
Sacramento River ◽  
Floodplain Wetlands ◽  
Floodplain Wetland ◽  
Juvenile Chinook Salmon ◽  
Juvenile Chinook ◽  
Detrital Carbon

AbstractDifferences in basal carbon sources, invertebrate density and salmon growth rate were observed in food webs across a lateral transect of aquatic habitats in the Sacramento River Valley, California. Similar to many large river valleys globally, the Sacramento River Valley has been extensively drained and leveed, hydrologically divorcing most floodplain wetlands and off-channel aquatic habitats from river channels. Today, the former floodplain is extensively managed for agriculture and wildlife habitat. Food web structure and juvenile Chinook Salmon (Oncorhynchus tshawytscha) growth were compared in three aquatic habitat types–river channel, a perennial drainage canal in the floodplain, and agricultural floodplain wetlands, which was seasonally inundated to provide bird and fish habitat during the non-agricultural growth season (late winter). Zooplankton densities on the floodplain wetland were 53 times more abundant, on average, than in the river. Juvenile Chinook Salmon raised on the floodplain wetland grew at mm/day, a rate 5x faster than fish raised in the adjacent river habitat (0.18 mm/day). Mean water residence times calculated for the floodplain agricultural wetland, perennial drainage canal and Sacramento River were 2.15 days, 23.5 seconds, and 1.7 seconds, respectively. Carbon in the floodplain wetland food web was sourced primarily through heterotrophic detrital pathways while carbon in the river was primarily autotrophic and sourced from in situ phytoplankton production. Hydrologic conditions typifying the ephemeral floodplain-shallower depths, warmer water, longer residence times and detrital carbon sources compared to deeper, colder, swifter water and an algal-based carbon source in the adjacent river channel-appear to facilitate the dramatically higher rates of food web production observed in floodplain verses river channel habitats. These results suggest that hydrologic patterns associated with winter flooding provide Mediterranean river systems access to detrital carbon sources that appear to be important energy sources for the production of fisheries and other aquatic resources.

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