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.

Trucking Central Valley Salmon Smolts from Hatcheries to Salt Water

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A November 1, 2023 article, originally published in High Country News and later posted in Maven’s Notebook, describes the practice of trucking juvenile salmon from hatcheries for release in salt water as a “culprit,” stating: 

According to a growing body of scientific evidence, it’s also the reason that many salmon are getting lost on their way back to their birth rivers, placing the future resilience of the species at risk…. These trucked hatchery fish may survive longer in the short term, but they will return to the river system years later with massive gaps in their memory and little sense of how to locate their spawning grounds. Instead, many end up wandering up unfamiliar rivers or streams and spawning far from home.

What the article doesn’t say is that juvenile salmon released directly in San Francisco Bay or San Pablo Bay, or in the ocean, are as much as ten to a hundred times more likely to live to spawn as are juvenile fish released near their hatcheries of origin.

It is true that trucked hatchery salmon smolts have a higher “straying” rate than smolts that are released near the hatcheries in which they were raised.  Sometimes, that difference in straying is quite dramatic.

On the other hand, while straying does cause salmon to wander into Central Valley rivers other than those from which they came, most of the rivers to which they stray would have few if any salmon at all if it were not for these strays.  And right now, trucking is necessary for the water projects to meet their mitigation goals of putting salmon back into the ocean to sustain salmon fisheries.

Furthermore, if it were not for trucking, the investment of hundreds of millions of dollars in salmon hatcheries would largely be for naught.  Only in wetter years do releases of hatchery-raised salmon near the hatcheries come anywhere close to achieving hatchery production goals.  In the drier years, when hatcheries provide their greatest benefit, very few fish released at or near the hatcheries survive downstream migration through Central Valley rivers and the Bay-Delta.

Trucking also reduces the competition between hatchery smolts and wild fish for limited habitat downstream of the Valley’s rim dams.

Below, I provide examples of straying rates for the Mokelumne Hatchery and Coleman Hatchery, from which some of the highest percentages of straying occurs.  The American and Feather River hatchery releases also have elevated straying of trucked smolts, but at much lower rates.

Mokelumne River Hatchery Straying

One of the greatest straying problems is from the Mokelumne Hatchery smolt releases, especially in drought years.  The Mokelumne Hatchery trucks more smolts percentage-wise than the other six salmon hatcheries.  However, coastal releases of Mokelumne Hatchery fish in drought years 2014 and 2015 yielded returns of 0.79-1.15% compared to 0.01% from the river release below the hatchery (Table 1).

However, straying rates for coast releases were greater than 50% to other rivers and hatcheries compared to 0% for the Mokelumne River releases (Figures 1-4).

Table 1.  Mokelumne Hatchery selected release groups – number and survival rates

 Coleman (Battle Creek) Hatchery Straying

Coleman Hatchery smolts trucked to the Bay have a much greater rate of straying than smolts released near the hatchery near the mouth of Battle Creek near Redding (Figures 5 and 6).  However, smolts released near the hatchery have a much lower survival/return rate (Table 2).

Table 2.  Coleman Hatchery selected release groups – number and survival rates.

Stray Counting

Other than showing up in these figures, strays are not accounted for in escapement estimates for individual rivers, and they are not counted in return tabulations of their hatchery of origin.  Fish counted at a hatchery or in river surveys simply get accounted for in the escapement estimate for the river to which they return.  As an example, tabulations for returns to the American River (Figure 7) show that in 2015, about a quarter of the tabulated escapement originally came as strays from the Mokelumne Hatchery.

Conclusion

It is good practice to reduce straying of hatchery salmon.  But in my view, arguments about straying often tend to obscure, not improve, the problems of poor survival of both wild and hatchery salmon in dry years due to inadequate flow and other aspects of poor water management.  And as long as commercial and sport salmon fisheries in California and Oregon are substantially dependent on hatchery production in the Central Valley, it makes a lot of sense to prioritize the survival to adulthood of hatchery salmon over their fidelity to natal rivers and streams.

For more on the trucking of juvenile hatchery production, see: https://calsport.org/fisheriesblog/?s=trucking&submit=Search

Figure 1. Returns from a Mokelumne Hatchery release to Golden Gate in 2014. Yellow dot is hatchery location. Green dot is release location.

Figure 2. Returns from Mokelumne Hatchery release to Santa Cruz Harbor in 2014.

Figure 3. Returns from Mokelumne Hatchery release to Moss Landing in Monterey Bay in 2015.

Figure 4. Returns from Mokelumne Hatchery release to lower Mokelumne River in 2014.

Figure 5. Coleman Hatchery 2014 smolt release group returns. Green dot is release site.

Figure 6. Coleman Hatchery 2014 smolt release group returns. Green dot is release site.

Figure 7. Green wedges are proportion of tags recovered in the American River in 2015 whose origin was the Mokelumne River Hatchery. Source: Pacific Fisheries Management Council.

Hunter’s Moon – Action Needed to Save Central Valley Salmon

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October has just ended, and the spawning of spring-run Chinook salmon should be nearing completion.  The winter-run have already finished spawning, and their eggs are now hatching.  The fall-run salmon are in the rivers and beginning their spawning on the Hunter’s Moon.  The fall-run are often neglected after the two endangered runs are complete.  There are actions needed now to protect this biggest and most important run.  After all, the California Fish and Game Commission sacrificed the commercial and sport salmon fishing this year to let the fall-run recover from record lows.

The first signs of trouble in 2023 came with the the low number of returning Central Valley spring-run Chinook Salmon this year.  The decline was indicative of a sudden drastic collapse in all the salmon runs around the Central Valley.

In the northern Sacramento Valley, there are the Clear Creek and Battle Creek spring-run populations.  In the middle Sacramento Valley, there are the Mill and Deer Creeks populations with their remnant counterparts in nearby Big Chico and Antelope Creeks.  There is also the relatively robust (until 2023) Butte Creek population.  Then there is the Feather-Yuba population in the lower Sacramento Valley.  Finally, there is the new population being restored in the upper San Joaquin River near Fresno.  An October 11, 2023 joint news release from NMFS and CDFW describes the numbers of returning spring-run this year as drastically low, to the point that fishery agencies have begun capturing the wild yearlings still residing in the spawning creeks and transporting them to a UC Davis conservation hatchery to preserve the species.

An immediate need is to focus attention on the fall-run Chinook that normally pour into the rivers and begin spawning with the Hunter’s Moon.  Water year 2023 was a wet year, and salmon fishing has been closed in anticipation of predicted low numbers in this year’s spawning run.  It turns out drought years 2021 and 2022 had worse-than-predicted effects on the Valley salmon.

The news release from NMFS and CDFW says, “While other year-classes (or cohorts) will return in coming years, the 2019-2022 drought impacted multiple cohorts, increasing risks for extirpation.”  Actually, 2019 was a wet year and 2020 was a below-normal water year.  It is brood-years 2020, 2021, 2022, and now 2023, that the 2021-2022 drought damaged from many different directions.  Looking ahead, there is a bad forecast for the coming years.  Poor brood years 2020-2023 will lead to poor brood years in 2024-2027, and so on, unless we pay attention now to this year’s fall run.

The Actions Needed Now – Starting the First of November:

1. An intensive monitoring program to assess the damage.

2. Remaining wild and hatchery salmon need maximum protection – this includes a temporary conservation hatchery.

3. This year’s production, no matter how minuscule, must be protected. A substantial portion of the juveniles should be rescued and preserved.  If water year 2024 turns dry this winter, fry, fingerling, and pre-smolt salmon from all races should be captured and eventually transported to the Bay unless significant strategic, coordinated flow pulses can be provided or occur naturally.

4. All hatchery smolts should have at least an adipose fin-clip mark. As many as possible should be released to the Bay or coast for maximum survival.  The marks will be important to differentiate between hatchery and natural-born salmon in the coming years.

5. At locations where migrating adult spring-run salmon potentially originating from Clear, Battle, Mill, Deer, and Butte creeks are clearly stuck or off-course during fall-winter-spring of water year 2024, and where it is possible to collect them, fish agencies should attempt to capture them and return them to their natal stream or to the conservation hatchery. Locations include weirs, dams, ladders, or traps, as well as hatcheries.  This will require Genetic Stock Identification (GSI).

6. Juvenile salmon salvaged at south Delta export facilities this winter and spring should be handled as follows: pre-smolt and smolt salmon should be transported to Golden Gate pens for release. Salvaged fry and fingerlings should be hatchery reared or pen reared to smolt size for eventual pen release at the Golden Gate.

7. The fish agencies and water managers must provide prescribed streamflows and water temperatures in spawning streams and in rearing and migratory reaches. They should not even consider Temporary Urgency Change Petitions for water supply.  Given the current storage in reservoirs across the state, they should prioritize fall and winter flows for salmon over reservoir storage.

8. Fall-run salmon hatcheries will be short of eggs this year. Some hatcheries may need to ship eggs to other hatcheries.  The American River Fish Hatchery in the past sorted adult strays from the Coleman Hatchery on Battle Creek and transported their eggs back to Coleman.

9. Hatcheries should increase the proportion of smolt production trucked to the Bay or coast, where survival rates are up to ten times higher than river releases.

Site-Specific Actions:

10. Yuba River – In the lower Yuba River downstream from Englebright Dam to Marysville streamflow should be immediately increased for spawning and incubation.  Target minimum streamflow should be at least 700 cfs from Englebright Dam to Marysville gage – through spring.

Chart of New Bullards Bar Reservoir

Figure 1. New Bullards Bar Reservoir has never been fuller at this time of year.

11. American River – Water temperatures should be lowered to 55oF to protect spawning salmon in this fall’s spawning season. This will require greater power bypass releases from the reservoir as begun in mid-October (Figure 2).  Folsom Reservoir is also “full.”

12. Upper Sacramento River – Streamflow should be maintained at a minimum of 7000 cfs (Figure 3) through the fall-winter-spring at Bend Bridge gage to provide good spawning, rearing, and emigrating conditions for salmon. Shasta Reservoir is also “full.”

13. Deer and Mill creeks – Streamflow from February through May should be maintained at a minimum of 100 cfs or higher to provide a clear migration corridor with water temperatures in the optimal range. Diversions should be disallowed when flows drop below 100 cfs in these months.

14. Butte Creek – Streamflow from February through May should be maintained to conform with the recommendations in the 2017 Draft Instream Flow Regime Recommendations Butte Creek.

15. Lower river migration corridors to and through the Delta – Water temperatures in winter and spring should be maintained below 60-65oF (see Figure 4), the lower the better. Striped bass still eat a lot of salmon at 65o

In conclusion, it is time for action.

chart of Water temperature in the lower American River at Watt Ave gage in September-October 2023 and 6-year average.

Figure 2. Water temperature in the lower American River at Watt Ave gage in September-October 2023 and 6-year average. Water temperatures need to be 55F by November 1. They should have been no higher than 60F in October.

Chart of streamflow in the upper Sacramento River at Bend Bridge gage in September-October 2023 and 59-year average.

Figure 3. Streamflow in the upper Sacramento River at Bend Bridge gage in September-October 2023 and 59-year average. Flows should be maintained near 7000 cfs through the fall.

Chart of water temperatures in spawning areas: Feather River at Gridley (GRL), Sacramento River from Keswick Dam (KWK) to Bend (BND), Stanislaus River at Ripon (RPN), American River at Watt Bridge (AWB), and Clear Creek at IGO (IGO).

Figure 4. Water temperatures in spawning areas should be below 55oF, while rearing and migration corridors should be below 60oF through spring. Spawning reaches include Feather River at Gridley (GRL), Sacramento River from Keswick Dam (KWK) to Bend (BND), Stanislaus River at Ripon (RPN), American River at Watt Bridge (AWB), and Clear Creek at IGO (IGO). Migration and rearing corridors include lower San Joaquin River at Mossdale (MSD), upper Sacramento River at Red Bluff (RDB), lower Sacramento River at Wilkins Slough (WLK) and Freeport (FPT). Blue dotted line is spawning temperature limit. Red dotted line is rearing and migration limit.

American River Salmon – Fall 2023

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It is early October 2023, and the fall-run salmon are running.  The California Department of Fish and Wildlife expects to open the ladder to the American River Hatchery on or about November 1.  There are already salmon in the lower American River from its mouth all the way to Nimbus Dam.

The run expected this year has a mixed forecast.  There was no ocean or river salmon fishery this year because of poor runs in the Central Valley during the 2020-2022 drought.  The fact that fishing was not allowed will improve the 2023 run size (escapement).  The 2020 run (parents of this year’s run) was pretty good (Figure 1).  But when brood year 2020 was rearing and migrating to the ocean, it was a critical drought year 2021, conditions under which juvenile salmon almost always have poor success in making the journey from rivers to the ocean.

Conditions in 2023 have been a mixed bag for the migration of adult spawners from the Bay to Central Valley rivers.  Summer 2023 started with warm water and low flows.  That changed when the Fall X2 requirement kicked in September (Figure 2).  The September Fall X2 flow pulse helped cool the lower Sacramento River and the Bay-Delta (Figure 3), and provided attraction flows for the adult salmon to move into the Bay and on toward the rivers.

An unforeseen problem has faced the running salmon when they hit the north Delta and mouth of the American River: water temperatures have been stressful for migrating adult salmon (>65oF, Figure 4) despite high flows (3000 cfs) from the American River.  The water quality standard for the lower American River requires water temperatures to be maintained <65oF in summer.  But water temperatures rose through September, with continuing increased water temperatures of water released from Folsom Reservoir (Figure 5).  Water year 2023 was a very wet year with above-average reservoir storage.  So why was the American River so warm?

The answer is that the powerhouse intakes at Folsom Dam had limited access to the cold-water pool, and the supply of accessible cold water was running short.  To ensure colder water for the hatchery and river for the November spawn, the Bureau of Reclamation began operating the powerhouse intakes in September to draw warmer water from the surface layers of the reservoir as the reservoir slowly drained.

The water temperature for spawning needs to be below 56oF.  Getting the temperature down that low by November is a tall order, but it was achieved in the 2020-2022 drought (Figure 6) under much lower reservoir storage levels (the present level is 135% of average for October and is much higher than in 2020-2022).  Reclamation achieved November spawning temperatures in those drier, lower-storage years by releasing substantial cold-water from the lower dam outlets, bypassing the power intakes.   The power bypass measure will likely be needed again in 2023 to meet the November temperature targets in the river.

There is a case to be made that Reclamation should also have used the power bypass in September 2023 to maintain 65oF at the Watt Avenue bridge.  Reclamation’s reluctance to use the power bypass to maintain release water temperature requirements further highlights the need for Reclamation to complete the planned refinements to the Folsom powerhouse intake system that will allow both continuous power generation and greater access to Folsom’s cold-water pool.

How else could this series of events have been avoided or at least improved?

First, summer flows in the lower Sacramento River should have been higher to help keep water temperatures at or closer to the standard of 68oF (see Figure 3) at the Wilkins Slough gage, located  on the lower Sacramento River upstream of the mouths of the Feather and American rivers.  Flows at Wilkins Slough for wet year 2023 were well below the average for water years 1994-2003, when salmon did relatively well (Figure 7).  These low flows in 2023 contributed to poor conditions in the lower Sacramento River, the Delta, and the Bay.

Second, the water temperature in the  lower American River at the Watt Avenue Bridge (AWB) should have met the water quality standard of 65oF until September, and should be kept below 60oF in October (Figure 8).  After November 1, Reclamation should maintain temperatures below 56oF for spawning.

Such improved conditions would improve the health of adult salmon spawning in the American River and its hatchery, as well as in other rivers and streams in the Sacramento River watershed.

Figure 1. Escapement (run size) for in-river spawning fall-run salmon in the lower American river 1952-2022.

Figure 1. Escapement (run size) for in-river spawning fall-run salmon in the lower American river 1952-2022.

Figure 2: Flow and water temperature at the Rio Vista Bridge July 15 – September 30, 2023.

Figure 2: Flow and water temperature at the Rio Vista Bridge July 15 – September 30, 2023.

Figure 3. Air and water temperature on the Sacramento River at Red Bluff (River Mile – RM - 240), and water temperature at Wilkins Slough (RM 120), Freeport (RM 50), and Rio Vista Bridge (RM 25). Also shown is water temperature standard at Red Bluff and Wilkins Slough.

Figure 3. Air and water temperature on the Sacramento River at Red Bluff (River Mile – RM – 240), and water temperature at Wilkins Slough (RM 120), Freeport (RM 50), and Rio Vista Bridge (RM 25). Also shown is water temperature standard at Red Bluff and Wilkins Slough.

Figure 4. Water temperature in the upper Sacramento River below Keswick Dam (RM 300), lower American River at Watt Avenue Bridge (AWB), the lower Feather River at Gridley gage (GRL), the lower Sacramento River at Wilkins Slough (WLK, RM 120) upstream of the Feather and American Rivers, and Freeport (FPT, RM 46) downstream of the American River.

Figure 4. Water temperature in the upper Sacramento River below Keswick Dam (RM 300), lower American River at Watt Avenue Bridge (AWB), the lower Feather River at Gridley gage (GRL), the lower Sacramento River at Wilkins Slough (WLK, RM 120) upstream of the Feather and American Rivers, and Freeport (FPT, RM 46) downstream of the American River.

Figure 5. Daily average water temperatures in the lower American River 9/10-10/3 2023 below Folsom Dam (AFD), at Fair Oaks gage below Nimbus Dam (AFO), at William Pond gage (AWP), and at Watt Avenue Bridge gage (AWB). The water quality standard in all water year types is 65oF maximum (year-round) at AWB.

Figure 5. Daily average water temperatures in the lower American River 9/10-10/3 2023 below Folsom Dam (AFD), at Fair Oaks gage below Nimbus Dam (AFO), at William Pond gage (AWP), and at Watt Avenue Bridge gage (AWB). The water quality standard in all water year types is 65oF maximum (year-round) at AWB.

Figure 6. September through December daily average water temperatures of Folsom Dam releases 2020-2022. Note the sharp drops in water temperatures in middle October from Power Bypass cold-water releases to provide target spawning temperatures (56oF).

Figure 6. September through December daily average water temperatures of Folsom Dam releases 2020-2022. Note the sharp drops in water temperatures in middle October from Power Bypass cold-water releases to provide target spawning temperatures (56oF).

Figure 7. Average daily flows in the lower Sacramento River at Wilkins Slough, upstream of the mouths of the American and Feather rivers in 2023, compared to the average during the decade of strong escapement 1994-2003.

Figure 7. Average daily flows in the lower Sacramento River at Wilkins Slough, upstream of the mouths of the American and Feather rivers in 2023, compared to the average during the decade of strong escapement 1994-2003.

Figure 8. Water temperatures in the lower American River at Fair Oaks (below Nimbus Dam) June-September 2023 with average from prior eight years that included 5 critical dry years.

Figure 8. Water temperatures in the lower American River at Fair Oaks (below Nimbus Dam) June-September 2023 with average from prior eight years that included 5 critical dry years.

Super Moon #4 – Harvest Moon (9/28/23)

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The Harvest Moon is the full moon nearest the autumn equinox (in 2023, the equinox was on 9/22).  The Harvest Moon greets fall-run salmon returning from the ocean to the Central Valley.  Unlike the previous two full moons, the 2023 Harvest Moon is coincident with improved conditions for fish.

The last two full moons, the Sturgeon Moon and the Blue Moon, wreaked havoc on the Bay by contributing to warm water and algae blooms (Figure 1) and to the associated low dissolved oxygen levels that led to sturgeon mortality in the Bay (Figures 2-4).  Low Delta water inflows and outflows contributed to the problems.1  The fish kills that occurred in the Bay were generally a consequence of poor water quality brought on by high summer water temperatures, associated algae blooms, and low dissolved oxygen levels (hypoxia).

Water temperatures above 20oC/68oF bring about stressful conditions, while those above 22oC/72oF lead to lethal conditions such as those that occurred in summer 2022 and summer 2023.  Other effects of warm water include plankton blooms and low dissolved oxygen levels that result from the algae die-offs after such blooms.  Though there is no direct evidence of the magnitude of mortality events, there is evidence that such events may have occurred in the Bay in summer 2022 and summer 2023.  Summer conditions in 2022 and 2023, and perhaps prior years, were likely major trauma incidents that had significant short-term and perhaps long-term effects on the sturgeon populations of the San Francisco Bay Estuary (Bay-Delta Estuary).

The warm water and algae blooms in the Bay abated early in September 2023.  Water quality improved with the advent of cooler air temperatures and with the higher Delta outflows (Figure 5) associated with the Fall X2 requirement from the Delta Smelt Biological Opinion (US Dept. of Interior).  The cooling of the water ensured that salmon could safely make their fall runs into the Central Valley rivers during the Harvest Moon, the last super moon of 2023.

Figure 1. River water stage (elevation) and water temperature at Rio Vista Bridge in Sacramento River channel of the Delta near exit to the Bay. Stage drops (draining of the Delta toward Bay) occurred prior to and after the four Super Moons of summer 2023. Note the warm water (74-75oF) draining from the Delta during the two mid-summer drain periods.

Graph of Water temperature (C), dissolved oxygen (DO, mg/l), and chlorophyll (mg/l) in western Suisun Bay in summer 2023.

Figure 2. Water temperature (C), dissolved oxygen (DO, mg/l), and chlorophyll (mg/l) in western Suisun Bay in summer 2023. Note algae bloom at end of July that began during the warm water period. Note very low DO (<6 mg/l) after bloom die-off in August.

Graph of Chlorophyll concentration (mg/l) in 2022 and 2023 in Suisun Bay.

Figure 3. Chlorophyll concentration (mg/l) in 2022 and 2023 in Suisun Bay. Note two summer algae blooms in red circles.

Graph of Dissolved oxygen concentration (mg/l) in 2022 and 2023 in Suisun Bay.

Figure 4. Dissolved oxygen concentration (mg/l) in 2022 and 2023 in Suisun Bay. Note low levels after two summer algae blooms in red circles.

Graph of Daily average flow in summer 2023 and 25-year average at Rio Vista in the lower Sacramento River channel of the Delta leading into Suisun Bay. Late August and September increases are related to the Fall X2 requirement of Delta water projects in wet years.

Figure 5. Daily average flow in summer 2023 and 25-year average at Rio Vista in the lower Sacramento River channel of the Delta leading into Suisun Bay. Late August and September increases are related to the Fall X2 requirement of Delta water projects in wet years.

Sturgeon Moon #3 – August 30 Blue Moon

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August 2023 has come to an end, following the second “Super Moon” of the month – a Blue Moon. The first full moon of the month was called a “Sturgeon Moon,” originally coined in reference to the ease of catching sturgeon in the Great Lakes during a full moon in summer. The cycle began with the quarter moon and neap tide on July 24 until the full moon on August 1.1

This year’s Super Moons have made a mess of San Francisco Bay, as they did in summer 2022. This year’s August moons have again, regrettably, led to a die-off of sturgeon and other Bay fish.2 The Super Moons’ strong tides caused warm water from the Delta to drain into the Bay, making the usually cool Bay unseasonably warm. (The ocean Blob may have added to some of this summer’s warm Bay water.) The warm water and the associated algal blooms (and their die-offs) have led to unprecedented low dissolved oxygen levels in the Bay, which can kill fish.

While the degree of harm has not been as bad as last year’s summer blooms that were aggravated by the 2022 drought, this year’s algal blooms have also harmed fish despite generally beneficial wet-year conditions. Last summer, there was die-off of nearly a thousand adult white sturgeon in the greater San Francisco Bay due to algal blooms. More dead white sturgeon adults also showed up on Bay beaches again this summer.3

The Bay turned warmer under this summer’s Super Moons than under those last summer (Figure 1). Blooms are still happening, as indicated by high turbidities and chlorophyll levels in portions of the Bay (Figures 1-3). The draining of warm Delta water to the Bay just before the 2023 Super Moons (Figures 4 and 5) warmed the Bay (Figure 6). Low dissolved oxygen continues to plague the Bay (Figure 6). The most recent bloom is depicted in Figures 7 and 8.

The summer 2023 Super Moons and their algal blooms make a complicated story, with the effects of various factors implicated in the blooms, and their role in fish die-offs in the Bay, yet to be fully determined. My concern centers on how warm the Delta becomes in summer before it drains into the Bay during the lunar tidal cycles (Figure 9). The lower rivers and Delta received too little flow from major Central Valley reservoirs for a wet year with full reservoirs. This is an increasing trend that deserves a lot more attention to ensure protection of the Bay’s fish and other public trust values. Otherwise, the trend will simply be chocked up to climate change.

Graph of North Bay (San Pablo Bay at Richmond Bridge) water temperature and turbidity in summer 2023.

Figure 1. North Bay (San Pablo Bay at Richmond Bridge) water temperature and turbidity in summer 2023. Note the presence of the three blooms indicated by high turbidity levels (>100 FNUs)

Graph of Chlorophyll levels at Martinez CA gage between East and North San Francisco Bay in summer 2023.

Figure 2. Chlorophyll levels at Martinez CA gage between East and North San Francisco Bay in summer 2023. Note three periods (green circles) of blooms located at this site.

Graph of Chlorophyll levels at Grizzly Bay gage (in northwest East Bay) in summer 2023.

Figure 3. Chlorophyll levels at Grizzly Bay gage (in northwest East Bay) in summer 2023.

Graph of Salinity (EC) at eastern Suisun Bay gage (in east Bay) in summer 2023.

Figure 4. Salinity (EC) at eastern Suisun Bay gage (in east Bay) in summer 2023. Red arrows indicate periods of draining prior to and between full moons.

Graph of Daily average (tidally filtered) discharge at Pittsburg gage in Suisun Bay summer 2023.

Figure 5. Daily average (tidally filtered) discharge at Pittsburg gage in Suisun Bay summer 2023. Red circles indicate drainage rates to Suisun Bay prior to two Super Moons (August 1 and 30).

Graph of Hourly dissolved oxygen levels in Grizzly Bay in summer 2023.

Figure 6. Hourly dissolved oxygen levels in Grizzly Bay in summer 2023. Note inverse relationship with chlorophyll levels in Figure 4. The low dissolved oxygen levels (<5 mg/l) began with the first bloom (August 1) and continued through August. Also note the Bay water quality standard is a minimum 6 mg/l dissolved oxygen level for fish health.

Satellite imagery of chlorophyll levels in San Francisco Bay on 8/29/2023.

Figure 7. Satellite imagery of chlorophyll levels in San Francisco Bay on 8/29/2023.

Graph of water temperature, chlorophyll, and salinity in Suisun Bay in summer 2023.

Figure 8. Water temperature, chlorophyll, and salinity in Suisun Bay in summer 2023. Note algal bloom in late August that began after the late-August draining of the Delta into the Bay when water temperatures reached 24oC (75oF).

Graph of San Francisco Bay water temperatures from 2007-2023.

Figure 9. San Francisco Bay water temperatures from 2007-2023. Note 2023 reached 70oF (see Figure 2) a recent record reached not even reached in critical drought years 2014, 2015, and 2022.

  1. Spring tides always happen when the Moon is at the full or new phase, which is when the Sun, Moon and Earth are in alignment. Neap tides occur around the first and last quarter phase of the Moon, when the Moon’s orbit around Earth brings it perpendicular to the Sun. ↩
  2. https://calsport.org/fisheriesblog/?p=4398 ↩
  3. https://www.sfchronicle.com/climate/article/fishkill-18279379.php ↩