Fish Food on Floodplain Farm Fields 2019, 2021, and 2022

2019 Water Year (October 1, 2018 through September 30,
2019) In the winter and spring of 2018-2019, 5,000 acres of agricultural
land in Yolo County, California was intentionally flooded. These
“dry-side” rice fields, although on the former floodplain of the
Sacramento River, are separated from the fish-bearing Sacramento
River (the “wet-side”) by high flood levees. Today, levees cut off
95% of the Central Valley’s floodplains from river channels so
that Central Valley aquatic ecosystems no longer recruit
floodplain the food web resources needed to support robust aquatic
food webs, create fish biomass and sustain abundant fish
populations. In this experiment we asked whether floodplain food web resources
“grown” in intentionally inundated “dry-side” agricultural fields
could be exported back to the river via flood drainage
infrastructure. If so, we were interested to know whether those
resources could improve juvenile salmon foraging success and
increase growth rates. In order to test these questions, we caged
fish in the floodplain drainage canal, at the location where the
floodplain drainage water entered the river and at locations both
up- and downstream. We hypothesized that zooplankton abundance and
fish growth rates would be elevated at the managed floodplain
outfall location, relative to the upstream location. We measured
water quality parameters, zooplankton species assemblage and
abundance, and juvenile Chinook salmon growth rates with PIT
tagged, hatchery-origin fish confined to enclosures at the study
locations. The 5,000 acres of managed floodplain was drained over
the coarse of 5 weeks in February and March, 2019 at a maximum
rate of 1,000 cfs. The Sacramento River flow during the experiment
ranged from 20,000-30,000 cfs. Fish growth rates at the floodplain
outfall location were up to five times greater than growth rates
upstream of the outfall and enclosure fish experienced growth rate
benefits at least up to a mile downstream from the managed
floodplain outfall. This study demonstrated a management practice that transfers
floodplain food web benefits from managed floodplains without
anadromous fish access, to the food-scarce Sacramento River
ecosystem. Multiple districts across the Sacramento Valley
maintain similar water infrastructure to what was used in this
pilot action. If incorporated at large scale into water management
practices, fish food production on “dry-side” agricultural fields
and wildlife refuges could contribute substantial food resources
to rearing and out-migrating juvenile salmon populations in the
Sacramento River system. 2020 Water Year (October 1, 2019 through September 30,
2020) No Fish Food project was implemented this year. 2021 Water Year (October 1, 2020 through September 30,
2021) In the winter and spring of 2020-2021, 8,775 acres of agricultural
land in Yolo County, California was intentionally flooded. These
“dry-side” rice fields, although on the former floodplain of the
Sacramento River, are separated from the fish-bearing Sacramento
River (the “wet-side”) by high flood levees. Today, levees cut off
95% of the Central Valley’s floodplains from river channels so
that Central Valley aquatic ecosystems no longer recruit
floodplain the food web resources needed to support robust aquatic
food webs, create fish biomass and sustain abundant fish
populations. In this experiment we asked whether floodplain food web resources
“grown” in intentionally inundated “dry-side” agricultural fields
could be exported back to the river via flood drainage
infrastructure. If so, we were interested to know whether those
resources could improve juvenile salmon foraging success and
increase growth rates. In order to test these questions, we caged
fish in the floodplain drainage canal, at the location where the
floodplain drainage water entered the river and at locations both
up- and downstream. We hypothesized that zooplankton abundance and
fish growth rates would be elevated at the managed floodplain
outfall location, relative to the upstream location. We measured
water quality parameters, zooplankton species assemblage and
abundance, and juvenile Chinook salmon growth rates with PIT
tagged, hatchery-origin fish confined to enclosures at the study
locations. The 8,775 acres of managed floodplain was drained over
the coarse of 5 weeks in February and March, 2021 at a maximum
rate of 1,000 cfs. The Sacramento River flow during the experiment
ranged from 3,000-12,000 cfs. Fish growth rates at the floodplain
outfall location were up to twelve times greater than growth rates
upstream of the outfall and enclosure fish experienced growth rate
benefits at least up to six miles downstream from the managed
floodplain outfall. This study demonstrated a management practice that transfers
floodplain food web benefits from managed floodplains without
anadromous fish access, to the food-scarce Sacramento River
ecosystem. Multiple districts across the Sacramento Valley
maintain similar water infrastructure to what was used in this
pilot action. If incorporated at large scale into water management
practices, fish food production on “dry-side” agricultural fields
and wildlife refuges could contribute substantial food resources
to rearing and out-migrating juvenile salmon populations in the
Sacramento River system. 2022 Water Year (October 1, 2021 through September 30,
2022) In the winter and spring of 2021-2022, 9,943 acres of agricultural
land in Yolo County, California was intentionally flooded. These
“dry-side” rice fields, although on the former floodplain of the
Sacramento River, are separated from the fish-bearing Sacramento
River (the “wet-side”) by high flood levees. Today, levees cut off
95% of the Central Valley’s floodplains from river channels so
that Central Valley aquatic ecosystems no longer recruit
floodplain the food web resources needed to support robust aquatic
food webs, create fish biomass and sustain abundant fish
populations. In this experiment we asked whether floodplain food web resources
“grown” in intentionally inundated “dry-side” agricultural fields
could be exported back to the river via flood drainage
infrastructure. If so, we were interested to know whether those
resources could improve juvenile salmon foraging success and
increase growth rates. In order to test these questions, we caged
fish in the floodplain drainage canal, at the location where the
floodplain drainage water entered the river and at locations both
up- and downstream. We hypothesized that zooplankton abundance and
fish growth rates would be elevated at the managed floodplain
outfall location, relative to the upstream location. We measured
water quality parameters, zooplankton species assemblage and
abundance, and juvenile Chinook salmon growth rates with PIT
tagged, hatchery-origin fish confined to enclosures at the study
locations. The 9,943 acres of managed floodplain was drained over
the coarse of 5 weeks in February and March, 2022 at a maximum
rate of 300 cfs. The Sacramento River flow during the experiment
ranged from 3,000-5,000 cfs. Fish growth rates at the floodplain
outfall location were up to three times greater than growth rates
upstream of the outfall. This study demonstrated a management practice that transfers
floodplain food web benefits from managed floodplains without
anadromous fish access, to the food-scarce Sacramento River
ecosystem. Multiple districts across the Sacramento Valley
maintain similar water infrastructure to what was used in this
pilot action. If incorporated at large scale into water management
practices, fish food production on “dry-side” agricultural fields
and wildlife refuges could contribute substantial food resources
to rearing and out-migrating juvenile salmon populations in the
Sacramento River system.