The Enhanced Delta Smelt Monitoring (EDSM) caught only 1 Delta smelt in 2200 smelt-targeted net tows in 2021. This compares to 49 captured in 2020 and hundreds in prior years. None were captured in the Spring Kodiak Trawl 2021 survey (Figure 1). This year’s results indicate that Delta smelt are likely virtually extinct in the wild.
Figure 1. Spring Kodiak Trawl survey index of Delta smelt (2004-2021), in which none were caught in 2021. Only one was captured in 2020. (source)
In a 6/15/21 post, I had a grim outlook for longfin smelt for the summer of critical drought year 2021. My concern has proven warranted.
The June Townet Survey (6/7-6/10) found longfin juveniles concentrated in the Sacramento River channel of the western Delta (Figure 1) in water temperatures of 19-21ºC (Figure 2), very close to stressful, low growth, poor survival conditions for longfin (>20ºC). The area was within the low salinity zone, where juvenile smelt concentrate in spring. In conditions of low Delta outflow in drought years like 2021, the low salinity zone encroaches into the western Delta, where the zone is prone to warming without the cooler Bay air temperatures. The zone remained in the western Delta through the summer of 2021, with sustained water temperatures of 21-23ºC.
The September Midwater Trawl Survey collected only one longfin smelt, a minimum catch for that survey (Figure 3). This catch total was similar to those observed in late summer of other drought years (07-08, 15, and 20).
A 2017 paper by UC Davis scientists concluded that extinction of Delta smelt and longfin smelt was not inevitable if the necessary recovery actions were soon implemented. The paper’s recommended actions have as yet not been implemented, and conditions have even become worse in recent years, especially in the 2021 drought. Delta smelt are now virtually extinct in the wild, with longfin smelt likely to follow soon.
Figure 1. Catch per unit effort of longfin smelt in survey #1 of CDFW/IEP Townet Survey in June 2021.
Figure 2. Water temperature in lower Sacramento River channel in western Delta in early June 2021.
Escapement of American River fall-run salmon dropped after recent drought years (2013-2015, Figure 1). It is reasonable to expect it would fall again in 2022 and 2023 as a consequence of the 2020-2021 drought period.
In a November 2, 2021 post, the California Department of Fish and Wildlife (CDFW) announced a plan to increase releases of hatchery smolts from its Nimbus Fish Hatchery on the American River in 2022, from the normal 4 million to 4.5 million. CDFW’s post stated in part:
“Chinook salmon returns to the American River declined significantly during California’s last drought,” said Jason Julienne, supervisor for CDFW’s North Central Region fish hatcheries. “We’re using those observations and that experience to get ahead of any population declines this time around by increasing production to help sustain this important salmon run.”
In a June 2020 post, I summarized annual hatchery releases of American River fall-run salmon smolts for years 1991-2019. I suggested that the long-term declines in escapement were also due to reductions in overall smolt releases and to an increasing proportion of river releases as opposed to Bay releases in drier years (Figure 2).
In 2020, a total of 4.44 million smolts were released, with 2.63 million released to the river and 1.81 million to the Bay (Figure 3). The 1.6-million smolts released in-river in May 2020 were subject to low flows in the river and the Delta and to high water temperatures (Figures 4 and 5). As a consequence, I would expect 2022 escapement to follow the general downward trend.
In drought year 2021, all 4 million smolts were trucked and released to the Bay. However, I still expect 2023 escapement to be reduced as a consequence of the generally poor survival of smolts released to the Bay in drier years with low Delta outflow.1
Until flow conditions in the river and Bay in dry years improve, a 12.5% increase in hatchery smolt releases is unlikely to improve escapement to recent historical levels.
Figure 1. American River fall-run escapement to river and hatchery 1975-2020.
Figure 2. American River hatchery smolt releases to Bay and river 1991-2019.
Figure 3. American River hatchery smolt releases to Bay and river in 2020.
Figure 4. American River streamflow and water temperature in spring 2020.
Figure 5. Sacramento River water temperature below the mouth of the American River near Freeport in spring 2020.
The Scott and Shasta rivers, California tributaries to the Klamath River, received irrigation curtailment orders from the State Water Resources Control Board September 10 of this drought year. The Shasta River responded well to the curtailment orders, and flows subsequently improved even more when the irrigation season ended on 10/1 (Figure 1). In contrast, the Scott River showed little response to curtailment (Figure 2). The Shasta River salmon counts reported by the California Department of Fish and Wildlife as of October 18th were 6,659, whereas the Scott River count was only 23.
Heavy rains in late October improved river flows, reduced the need to irrigate pastures and hayfields, and have allowed Chinook and Coho salmon to freely ascend both rivers to spawn. The Salmon River, a third large tributary that enters the Klamath downstream of the Scott, responded similarly to the storms (Figure 3).
Figure 1. Streamflow in the Shasta River Sep-Oct, 2021.
Figure 2. Streamflow in the Scott River Sep-Oct, 2021.
Figure 3. Streamflow in the Salmon River Sep-Oct, 2021.
A modest production of winter-run salmon fry was achieved in the Sacramento River near Redding this summer (Figure 1).1 With the recent storm that peaked on October 24, these young salmon are now moving down the river toward the Delta (Figure 2).
Upon entering the Delta, these young salmon face the grim fate of passing through the Delta Cross Channel (DCC)/and Georgiana Slough into the central and south Delta, where they are drawn to Delta pumps by sharply increased exports (Figure 3).
The diversion of Sacramento flows increases with the periodic opening of the Delta Cross Channel (Figure 4). On an outgoing tide, the diversion via the DCC and GS can be higher than 50% under these circumstances.
Once they enter the interior Delta, it is difficult for young salmon to navigate out to the Bay. Many are drawn with reverse net flows to the south Delta, especially in periods when the DCC is closed. The risks to salmon fry in Clifton Court Forebay (predation) and at fish facility screens are severe.
Closing the DCC during the flow pulse only increases flow through Georgiana Slough and traps any diverted salmon in the interior Delta. Keeping the DCC open minimizes the reverse flows in the interior Delta, but draws more salmon in. It is a tough call either way. So the best option for this first fall pulse of winter-run fry is to minimize exports. This type of protection has been considered many times in the past. It is currently required in the Incidental Take Permit (p. 80) for the operation of the State Water Project, but not until after December 1.
Figure 1. Passage of juvenile winter-run salmon past Red Bluff, September-October 2021.
Figure 2. Catch of winter-run fry in lower Sacramento River near Wilkins Slough (RM 120) in fall 2021.
Figure 3. Graphic depiction of Delta net flow (cfs) conditions in late October 2021.
Figure 4. Hourly flows through Delta Cross Channel in October, 2021.