Science, Management, Issues, Problems, and Solutions
Welcome to the California Fisheries Blog
The California Sportfishing Protection Alliance is pleased to host the California Fisheries Blog. The focus will be on pelagic and anadromous fisheries. We will also cover environmental topics related to fisheries such as water supply, water quality, hatcheries, harvest, and habitats. Geographical coverage will be from the ocean to headwaters, including watersheds, streams, rivers, lakes, bays, ocean, and estuaries. Please note that posts on the blog represent the work and opinions of their authors, and do not necessarily reflect CSPA positions or policy.
I fully support implementation in 2024 of the Fall X2 action prescribed in the biological opinion for Delta smelt. Furthermore, I support maintaining Delta Outflow at 10,000-12,000 cfs year-round[1] in all water year types to protect Delta smelt and longfin smelt. The compelling reason for such action is to maintain the low salinity zone (LSZ) and the head of that zone downstream of the confluence of the Sacramento and San Joaquin rivers in the western Delta, on an average-daily or tidally-filtered basis (Figures 1 and 2).
Such action will require approximately 10,000-12,000 cfs daily average Delta outflow (Figure 3). Such action would ensure the LSZ is maintained downstream of the Delta within Suisun Bay, Suisun Marsh, and Montezuma Slough – conditions necessary to protect listed Delta and longfin smelt populations. Otherwise allowing the LSZ to enter the Delta subjects the pre-spawn staging of the smelts (Figures 4 and 5) to entrainment into Delta water exports and the vagaries of Delta habitat (poor water quality and food supply, as well as lower turbidity and higher predation). Failure to maintain the X2 in Suisun Bay below the confluence also undermines the integrity of the LSZ critical habitat of the smelt in future months. My conclusions are further amplified in prior comments in support of the Fall X2 (https://calsport.org/fisheriesblog/?p=2940).
In conclusion, failure to implement Fall X2 will have an adverse impact on Delta smelt and longfin smelt and their critical LSZ habitat.
Figure 1. Water temperature and salinity of eastern Suisun Bay near Pittsburg June-September 2024.
Figure 2. . Hourly and tidally filtered salinity of eastern Suisun Bay near Collinsville August-September 2024. Note X2 is approximately 2 psu (ppt)
Figure 3. Daily Delta outflow August-October in 2023, 2024, and average 2014-2023. Note application of Fall X2 in September 2023 (> 8,000 cfs).
Figure 4. October 2023 fall midwater trawl survey catch of longfin smelt.
Figure 5. October 2011 fall midwater trawl survey catch of Delta smelt.
[1] Except in critical drought years when exports are minimum due to minimum available water supply.
In a June 2024 post, I hypothesized factors controlling the white sturgeon population in San Francisco Bay-Estuary. I concluded the major factor controlling the adult stock size was periodic recruitment of juvenile sturgeon from successful spring spawning and early rearing in the lower Sacramento River. Successful recruitment only occurs in the wettest years, when there are higher streamflows and cooler water temperatures.
Recruitment of young white sturgeon in significant numbers has only occurred in three years since 2010: 2011, 2017, and 2023. Recruitment in 2024, an above normal water year, is likely to be poor. Production of young sturgeon is likely of function of attraction of spawners from San Francisco Bay (to high winter-spring river flows – good in 2024), good spawning conditions (streamflow and water temperatures – good in 2024), and good early rearing and transport conditions in the lower Sacramento River and the north and central Delta (streamflow and water temperatures – poor in 2024).
The adult spawning stock size may not be as important as spawning conditions, given strong recruitment in wet year 2023 under a very low stock abundance (observed Bay die-off in summer of critical drought year 2022).
There are a number of measures that hold promise to protect and enhance adult stock numbers, recruitment, and survival of white sturgeon.
Spawning Conditions
Flows in the lower Sacramento River (Wilkins gage) should be 8,000 to 10,000 cfs or higher in spring.
Flow in the lower Sacramento River (Wilkins Slough) should be at least 8,000-10,000 cfs.
Early Rearing and Juvenile Transport
Sacramento River inflows to the Delta should be at least 20,000 cfs in spring.
Flow from the lower Sacramento River into the Delta (Freeport) should be at least 20,000 cfs in spring and early summer (April-July).
Delta Conditions
The net flow in the lower Sacramento River channel downstream of the entrance to Georgianna Slough should be at least 10,000 cfs in spring and early summer (April-July). This will require total Delta diversions, including local agricultural diversions and exports by the State Water Project (SWP) and Central Valley Project (CVP), to be limited to approximately 10,000 cfs.
Flow in the lower Sacramento River in the Delta below Georgianna Slough should be at least 10,000 cfs in spring and early summer (April-July).
White sturgeon recruitment is best assessed at fish salvage facilities at the water project south Delta export pumps. Young sturgeon produced in the lower Sacramento River reach the Delta in early summer as shown here in 2023. Note the high export levels of 20,000 acre-feet per day (approximately 10,000 cfs; in this figure, SWP exports are shown behind CVP exports).
Bay Conditions
Delta outflow to the Bay should be at least 10,000 cfs from spring to early fall (April-October).
Delta outflow to the Bay (DTO) and Rio Vista water temperature May-Oct, 2021-2024. Recommended Delta Outflow is a minimum 10,000 cfs (purple line).
Minimize Sturgeon Adult Harvest and Pre-Adult Fishing Mortality
Sturgeon sport fishing should be limited to the Bay only, with catch-and-release regulations, with the following further considerations:
Fishing for sturgeon should be closed in the east Bay or north Bay if daily maximum water temperatures are expected to exceed 65ºF (18ºC) in any open water portion gage locations in either Bay portions (possible from late spring through early fall).
CDFW could allow limited harvest through short-term regulations, limited by slot (length range) and number. (Note that slot harvest in 2024 would allow a small harvest of broodyear 2011 white sturgeon, the most recent abundant broodyear in the adult population).
Under such restrictions, the effects of sport fishing on the sturgeon population would be minimal.
In addition, sturgeon collected at south Delta export salvage facilities should be transported to an appropriate location in the Bay for release (presently, they are released in the Delta).
Population abundance and recruitment of white sturgeon are mainly a function of annual Central Valley hydrology (river flow), with abundant juvenile production occurring only in the wettest years. Past harvest has only involved a small percentage of the adult population, while watershed hydrology has orders of magnitude greater effect on recruitment and eventual adult population abundance.
Allowing a limited fishery could also help in continuing to assess the health of the population. Sport fishers should be asked to contribute important information on the sturgeon they catch.
The fire that started on July 24 has burned most of the lower foothill and middle reaches of the affected streams as of August 8th. It is now actively encroaching on the mountain spawning reaches of Mill and Deer creeks on the south slopes of Mt Lassen, the two most important of the affected spawning streams (see maps below). It will likely slow only when it reaches the boundary of the 2021 Dixie Fire and its lower levels of fuels.
Map of Park Fire in northeast Sacramento Valley dated 8/3/2024. Red arrows indicate further fire growth as of 8/6, mainly in the upper Mill and Deer creeks watersheds. Green stripes indicate spring-run salmon summer holding and fall spawning reaches.
Spring-run salmon populations in the Central Valley, including the core Battle, Mill, Deer, and Butte Creeks populations, are at recent historic lows. It is essential to rehabilitate previously burned watersheds as soon as possible. The California Department of Fish and Wildlife should expand the Deer Creek Spring-Run Conservation Hatchery Program begun in 2023 at UC Davis to include the other spring-run salmon streams in the Sacramento Valley.
At the same time, it is important to attack the causes of poor survival of juveniles migrating to the ocean and poor survival of adults returning to the spawning grounds. In this regard, comments on the Environmental Impact Statement for the Long-Term Operations of the Central Valley Project and the State Water Project are due on September 9. Operations of these water projects play a major role in the survival of Central Valley salmon to and from the ocean. With the acceleration of climate change, it is important to re-evaluate the present and future effects of these water projects and potential operational changes to protect salmon under this new climate change baseline.
Park Fire active zone moving northeast in the upper Mill Creek watershed on August 8th, 2024. CALFIRE hopes to stop the Park Fire advance at highways 32/36 and the boundary of 2021 Dixie Fire (see next map).
Park Fire active zone moving northeast in the upper Mill Creek watershed on August 8th, 2024. CALFIRE hopes to stop the Park Fire advance at highways 32/36 and the boundary of 2021 Dixie Fire (see next map).
Western boundary (extent) of Dixie Fire in summer 2021.
It is the first summer without the reservoirs on the Klamath River. Upper river flows at Iron Gate are now at summer lows (900 cfs, Figure 1). The flow, water temperature, and turbidity in the river without the reservoirs (the dams have not all been removed) is shown in the following figures. Two major concerns are sporadic turbidity events from dropping flows and higher water temperatures that are a consequence of unshaded former reservoir reaches and loss of cold-water dam releases.
Extensive gaging data are available for the lower Klamath River from the USGS and Karuk Tribe (Figure 2). The focus here is on the reach below the four-dam-removal project where the dams were drained in early 2024, leaving the river free-flowing.
Late spring and early summer gage data show the upper reaches below Iron Gate had the warmest water in 2024 (Figures 3-5). Water temperatures reached 25oC/77oF, lethal to salmonids. Further downstream, water temperatures were gradually cooler as the river progressed toward the mouth, generally remaining in the 68-70oF maximum range after receiving cool tributary water and cooler air temperatures. Further upstream above Iron Gate, water temperatures were similar those immediately below Iron Gate (Figure 6).
Prior to dam removal, the upper reaches below Iron Gate had the lowest water temperatures in 2022 and 2023 (Figure 7 and 8), reflecting the release of cold water from the bottom of Iron Gate Reservoir. Without this source of cold water, the upper reaches are now significantly warmer in late spring and summer.
Because the water temperatures were similar in 2024 above and below the former Iron Gate Reservoir (see Figures 4 and 6), there seems to be little warming in the unforested former Iron Gate reservoir reach. The upper reach of river below Iron Gate Dam now generally reflects historic warm water characteristics of the 6-dam project reach between Klamath Lake and Iron Gate Dam. Future riparian forest restoration of the three former reservoir reaches may lead to some cooling of the upper river in the future.
Finally, the drop in river flow in early July 2024 (see Figure 1) appears to have caused additional reservoir-footprint erosion and scouring, leading to high turbidity levels below Iron Gate (Figure 9). Such turbidities like the warm water are generally lethal to salmonids.
Figure 1. Upper Klamath River flow at Iron Gate gage in June and early July 2024.
Figure 2. Lower Klamath River gauging stations from Klamath Lake downstream to mouth. Blue marker denotes gage below JCBoyle Dam. Numbers in green and yellow circles denote multiple gage locations.
Figure 3. Water temperatures in lower Klamath River in June 2024. Iron Gate Dam is uppermost location and Turwar Gage is lower-most location near mouth. Note greatest water temperatures were recorded from the two uppermost reaches: Iron Gate and Walker Bridge.
Figure 4. Water temperature recorded at Iron Gate gage 6/15-7/7 2024.
Figure 5. Water temperature recorded at Walker Bridge gage 5/20-7/7 2024.
Figure 6. Water temperature recorded at Fall Creek gage 6/1-7/7 2024.
Figure 7. Water temperatures in lower Klamath River in June-July 2022. Iron Gate Dam is uppermost location and Turwar Gage is lower-most location near mouth. Note lowest water temperatures were recorded from the two uppermost reaches: Iron Gate and Walker Bridge.
Figure 8. Water temperatures in lower Klamath River in June-July 2023. Iron Gate Dam is uppermost location and Turwar Gage is lower-most location near mouth. Note lowest water temperatures were recorded from uppermost reach: below Iron Gate.
Figure 9. Turbidity (suspended sediment) concentrations measured at Iron Gate Gage in 2024. Note original reservoir drawdown and subsequent reservoir sediment deposit erosion January-
In Above Normal water year 2024, an increase in summer freshwater flows released from reservoirs to the Bay-Delta estuary has proven a viable action to reduce threats to Central Valley fishes. Water management actions in early July heat waves alleviated extreme water temperatures that threaten the native fishes in rivers and the Bay-Delta. These actions can be described as adaptive management experiments to test their potential performance for the update of the State Board’s Bay-Delta Plan.
Actions
Increasing lower Sacramento River flow from 5000 cfs to near 8000 cfs has helped lower Wilkins Slough gage (WLK) water temperatures from 70-72oF to the water quality standard of 68oF (Figure 1), despite record-high air temperatures (Figure 2).
Increasing Delta inflow at Freeport (FPT) from 14,000 cfs to 20,000-22,000 cfs (a combination of increased Wilkins Slough, Feather River, and American River flows) has lowered Freeport water temperatures in the north Delta from 72oF to 70oF (Figure 1).
A rise in Delta outflow from 8,000 cfs to 12,000 cfs has helped reduce Rio Vista (RVB) water temperatures at the Delta’s exit to the Bay from 75-76oF during the early July heat wave to 72oF after the heat wave (Figure 2).
Benefits
The actions may not seem that dramatic, but they are very important to the river, Delta, and Bay environments and to the salmon, smelt, steelhead, sturgeon, and other native Central Valley fishes that depend on these habitats. Water temperatures in the 72-75oF range are highly stressful or lethal to these native fishes. Such temperatures favor non-native predatory and competing fishes. Water temperatures of 68-72oF are at the upper favorable limits for the native fish and are necessary to maintain viable growth, survival, and reproduction. These temperatures also help ensure that dissolved oxygen is adequate and that algae blooms do not reach excessive levels. In other words, they promote a healthier ecosystem. Water temperatures near or above 75oF, which occurred in the Delta of drought years 2021 and 2022 (Figure 3) under extreme low flows (Figure 4), are deadly to native Delta fishes.
Conclusion
Although water managers in 2024 probably did not have these bold actions in mind to save fish (flows were increased to allow maximum summer water diversions from the Delta), their fortuitous implementation clearly highlights early summer flow measures that should be included in the update of the Bay-Delta Plan. Two additional actions I would recommend are higher flows in the San Joaquin River to provide some minimal benefit to the San Joaquin’s native fish community, and reductions in water exports.
Figure 1. DTO = Delta Outflow to the Bay, FPT = Sacramento River Freeport gage, WLK = gage below Wilkins Slough on lower Sacramento River upstream of the Delta, RVB = Rio Vista Bridge in Sacramento River channel northwest Delta, near entrance to eastern Bay.
Figure 2. Average daily air temperatures at Red Bluff (KRDD) in Sacramento Valley, Modesto (KMOD) in San Joaquin Valley, and Rio Vista Bridge (RVB) in west Delta May-July 2024. Note Delta air temperatures are generally 5-15oF lower in the Delta than the valleys. Also note the record or near-record air temperatures in early July.
Figure 3. Average daily water temperatures in the north Delta channel of the Sacramento River at Freeport May-July 2021-2024 and average of years for decade 2001-2010.
Figure 4. Average daily (tidally filtered) streamflow in the north Delta channel of the Sacramento River at Freeport, May-July 2021-2024 and average of years for decade 2001-2010.
