Category Archives: Hatcheries

Enhancing Oroville Hatchery Salmon Contribution

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In a recent post, I discussed ways to increase returns/survival of the Coleman (Battle Creek) Hatchery produced smolts released to the Sacramento River and the Bay. In this post I focus on ways to improve returns/survival of young salmon produced at the Oroville (Feather River) Hatchery. Trucking smolts to the Bay in drier water years and releasing spring flow pulses in wetter years remain the key management actions for increasing the contribution of hatchery salmon to coastal and river fisheries. Timing of releases is also critical. While overall returns are highly influenced by ocean conditions, active management by hatchery managers (trucking, barging, and timing of releases) and water managers (flow pulses) are important tools in maximizing the contribution of hatchery smolts to salmon populations.

In a prior post, I discussed general means of increasing hatchery contributions. In that post, I presented a summary of Oroville (Feather River) Hatchery returns for brood years 2008-2012 (Figure 1). Return rates were highest for brood years 2009-2011, with winter-spring normal-wet year designations (water years 2010-2012). Brood year 2008 and 2012 smolts were released in winter-spring of drought years.

In this post I provide information from earlier brood years. This information supports a more specific strategy to increase the Feather River hatchery program’s contribution to California fisheries. Below, I add a summary of returns from selected brood years (2002-2007).

Figure 1. Feather River hatchery fall-run salmon return rates by release method for brood years 2008-2012 (release years 2009-2013). Source of data: http://www.rmpc.org/

Brood Year 2002

Hatchery smolt returns for brood year 2002 were good, with hatchery releases in the above-normal water year 2003. The good adult return performance is generally attributed to good river and ocean conditions in 2003. A closer look at release return rates (Figure 2) shows generally good returns (>1%) reflecting the good river and Delta conditions in 2003 and good ocean conditions, at least in 2003. Some return rates were very good (>2%), including late April to mid-May returns for Delta and Bay (non-pen) releases. The higher return rates occurred coincident with a late-April through mid-May flow pulse (Figure 3). During the flow pulse, releases to the Delta had return rates in the same high range as Bay releases. Most of the river releases had low rates of return (<1.0%) before the flow pulse; while during the pulse, most rates were 1.0-1.7%.

Figure 2. Feather River hatchery fall-run salmon return rates by release method for brood year 2002 (release year 2003). Source of data: http://www.rmpc.org/

Figure 3. Water temperature and mean daily river flow in the lower Sacramento River channel of the Delta at Freeport in spring 2003. (USGS chart)

Brood Year 2003

Hatchery smolt returns for brood year 2003 were mediocre. The juvenile salmon were released in the below-normal water year 2004. The poor performance is generally attributed to poor river conditions in 2004 and poor ocean conditions in 2004-2006. A closer look at release return rates (Figure 4) shows few good returns (>1%); this reflects the poor river and ocean conditions. Some Bay-release return rates were good (>1%). The higher Delta-release and Bay-release return rates occurred with higher early-to-mid April flows (Figure 5). May river releases had near-zero rates of return. Overall, Bay-release return rates (all with net pens) far outperformed Delta and river releases, reflecting the advantage of bypassing poor river and Delta conditions after mid-April in 2004.

Figure 4. Feather River hatchery fall-run salmon return rates by release method for brood year 2003 (release year 2004).

Figure 5. Water temperature and mean daily river flow in the lower Sacramento River channel of the Delta at Freeport in spring 2004. (USGS chart)

Brood Year 2004

Hatchery smolt returns for brood year 2004 were poor despite the fact that juvenile releases took place in the above-normal water year 2005. The poor performance is generally attributed to poor ocean conditions in 2005-06. A closer look at release return rates (Figure 6) shows poor returns (<1%) reflecting the poor ocean conditions. Some return rates were extremely poor (<0.01%). Compared to good return rates of 1-4% in other years (see Figure 1), these rates are extremely low. For example, a normal annual release of 4 million smolts from the Oroville Hatchery would return 40,000 adults at 1% and only 400 at 0.01%. A closer look at Figure 6 release rates and water conditions in spring 2005 (Figure 7) indicates higher survival of releases into the Feather River and Bay during the May flow pulse, although Bay release rates (all net pens) averaged twice those of river releases.

Figure 6. Feather River hatchery fall-run salmon return rates by release method for brood year 2004 (release year 2005).

Figure 7. Water temperature and mean daily river flow in the lower Sacramento River channel of the Delta at Freeport in spring 2005. (USGS chart)

Brood Year 2005

Brood Year 2005 releases in the very wet year 2006 had return rates that were very poor for both Delta and Bay releases, reflecting very poor ocean conditions (no chart shown). Delta releases averaged 0.1 % return, with Bay releases (no pens) only slightly higher at 0.2 %. These low rates, along with similar low rates from other Central Valley hatcheries, contributed to the salmon fishery collapse of 2008.

Brood Year 2006

Hatchery smolt returns for brood year 2006 were poor (Figure 8). The poor performance is generally attributed to poor river, Delta, and Bay conditions in the 2007-2009 drought, and mediocre ocean conditions. Many return rates were very poor (<0.1%). Some of the higher returns came from earlier releases (April), when Delta inflow was higher and water temperatures were lower (Figure 9).

Figure 8. Feather River hatchery fall-run salmon return rates by release method for brood year 2006 (release year 2007).

Figure 9. Water temperature and mean daily river flow in the lower Sacramento River channel of the Delta at Freeport in spring 2007. (USGS chart)

Brood Year 2007

Hatchery smolt returns for brood year 2007 were generally poor (Figure 10). The poor performance is generally attributed to poor river, Delta, and Bay conditions in the 2008-2009 drought, and relatively poor ocean conditions, except in 2010. Many return rates were very poor (<0.1%). Some Bay pen release return rates were good (>1.0%). Most of the lower return rates came from May river releases under poor conditions (Figure 11). Bay pen release return rates were generally substantially higher than non-pen Bay releases during May.

Figure 10. Feather River hatchery fall-run salmon return rates by release method for brood year 2007 (release year 2008).

Figure 11. Water temperature and mean daily river flow in the lower Sacramento River channel of the Delta at Freeport in spring 2008. (USGS chart)

Summary and Conclusions

In summary, return rates from Oroville Hatchery fall-run salmon smolt releases vary greatly with ocean, river, Delta, and Bay conditions, within and among years. With up to 6 to 8 million fall-run smolts released each year, highly variable return rates result in highly variable catches of adult fish in coastal and river fisheries and spawner escapement to rivers and hatcheries. Good years can yield 1 or 2 percent total returns – producing 60,000-160,000 adult salmon returns. Poor years may yield only 0.1% or less – just 6,000-16,000 adult returns. Factors affecting the return rate include:

  1. Ocean conditions.
  2. River, Delta, and Bay conditions.
  3. Release location – Feather River, lower Sacramento River below mouth of Feather, north Delta, San Pablo/North Bay, and coastal bays north and south of San Francisco.
  4. Release method – trucked to river, Delta, or Bay boat ramps for direct release, trucked to acclimation pens in Delta or Bay, or trucked to feeding pens in coastal bays.
  5. Age/size of released smolts – February through July: early spring smolts, normal spring smolts (mid-April to mid-May), and advanced late spring smolts (mid-May to mid-June). Late spring releases are limited to the Bay because the rivers and Delta are too warm.
  6. Date of release – winter release of hatchery fry and fingerlings, spring release of smolts, late spring and summer release of advanced smolts.

The following actions by hatchery and resource managers can enhance returns to a limited extent, depending on conditions.

  1. Trucking to lower Sacramento River, Delta, Bay, or coastal bays.
  2. Acclimating trucked fish in pens prior to release.
  3. Timing releases to best available release conditions.
  4. Enhancing release conditions (e.g., flow pulses).
  5. Barging smolts to the Bay from the lower Feather River.

The most problematic situation for managers is improving returns in years with very poor ocean conditions (e.g., 2006). Under such conditions, trucking to Bay pens appears to be the best option and is the present management scheme. Barging smolts to the Bay may provide an added benefit. Under good ocean, Bay-Delta, and river conditions, releases to river and Delta locations with a supplemental flow pulse may provide good returns. Releases to lower Feather River locations generally provide poor returns regardless of conditions.

A further enhancement option is rearing hatchery fry in floodplain rice fields adjacent to the lower Feather River. Besides the obvious benefit of “natural” rearing, high growth would allow smolt release at least a month earlier than hatchery smolts. Such natural smolts could be trucked or barged to the Bay from near the rearing sites. A return rate of 5-10% from such smolts is conceivable, with the potential of contributing substantially to coastal and inland salmon fisheries.

Another Fall-Run Salmon Crash – Bad Ocean Conditions Again? Or Bad River/Delta/Bay Conditions?

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NOAA Fisheries’ Northwest Fisheries Science Center states on its website1: “Similar to 2015, many of the ocean ecosystem indicators suggest 2016 to be another poor year for juvenile salmon survival, the second consecutive year of poor ocean conditions. The PDO2 was strongly positive (warm) throughout 2016, coinciding with the continuing of the anomalously warm ocean conditions in the NE Pacific initiated by the “The Blob” that began in the fall of 2013. Strong El Niño conditions at the equator also persisted throughout 2015 until May of 2016. Sea surface and upper 20 m water temperatures off Newport Oregon remained warmer than usual (+2°C) throughout most of 2016 continuing two consecutive years of anomalously warm ocean conditions.” See Figures below and at end for more details from NMFS presentation.

Mother Nature has once again dealt California salmon a deadly set of circumstances. There is not much that can be done at this point, because much of this bad hand has already been played during the 2012-2016 drought and the bad ocean conditions in 2015 and 2016. Reduction of the 2017 sport and commercial fisheries has been prescribed again to save the patient. Cutting salmon harvest is like applying a tourniquet to an amputation, yet it is necessary. Have we not learned to better prepare for such circumstances?

Once again, the blame for poor resource management is being shifted to poor ocean conditions. Evidence clearly indicates that poor inland river, Delta, and Bay conditions were also a major factor in the poor survival of salmon during the recent drought. Furthermore, evidence indicates that the fall-run hatchery salmon populations that make up most of the commercial and sport fishing catch were sustained through the drought by the transport of hatchery smolts to the Bay avoiding the poor river and Bay-Delta conditions. There was very poor survival of smolts released near upriver hatcheries during the drought compared to smolts trucked to the Delta or the Bay. This is strong evidence that the rivers and Delta are the key factors in Central Valley salmon viability.3

The same circumstances occurred in the 2004-2008 period, leading to the 2008 “salmon crash”. First came a sequence of drier years, 2001-2005; two bad ocean years, 2004 and 2005; then a flood year 2006; followed by drought years 2007 and 2008. The salmon populations did recover with better runs in 2012 and 2013 because of normal-wet river conditions in 2010-2012 and good ocean condition in 2010-2013, but the runs have since declined sharply, beginning in 2014 and culminating in the expected 2017 crash. So far, the 2017 fishery is better than expected because of the expanded hatchery transport efforts in 2014. The prognosis is not as good for the wild salmon that were not trucked to the Bay.

Declining runs in the drought years 2014 and 2015, poor young production from 2013-2015, and the poor run of two-year-old (jacks) from brood-year 2014 in 2016 are indicators of a population crash. The brood-year 2014 jacks were the consequence of cumulative bad conditions: (1) in their spawning run (summer-fall 2014), (2) during incubation and first year rearing-emigration (winter-spring 2015), (3) during their first two summers in the ocean (2015-2016), and (4) poor conditions during their run from the ocean in summer-fall 2016 from the drought hangover. Three-year-olds from the 2014 brood year are also expected to return in poor numbers in 2017, because of droughts during their parents’ spawn, poor river rearing conditions (2015), and then poor ocean conditions in 2015 and 2016.

The prognosis for brood-years 2015-2017 (2018-2020 runs) is not good for some of the same reasons, especially the expected poor numbers of spawners. These runs will carry hangovers from poor river and ocean conditions in 2015 and 2016.

One thing is lessening the overall effect on fisheries: trucking hatchery smolts to the Bay. While that is not helping the wild salmon populations in the Central Valley, or those hatchery populations not included in the trucking program, it is helping.

What can be done to improve all the salmon populations in the Central Valley?

  1. Reduce harvest of adults in ocean and rivers (being implemented).
  2. Increase hatchery production (take more eggs and rear more smolts).
  3. Diversify hatchery smolt production by rearing some fry in natural floodplain habitats.
  4. Increase hatchery smolt survival by trucking and barging to the Bay and pen acclimating in the Bay.
  5. Improve migration and pre-spawn holding conditions for wild and hatchery adult spawners by maintaining spring-fall migration conditions (flow and water temperatures) in lower rivers and spawning reaches.
  6. Maintain adequate water levels and water temperatures to sustain eggs and embryos until hatching and emergence.
  7. Provide optimum flows and water temperatures in rearing areas for growth and survival (minimize predation).
  8. Provide flow pulses to attract spawners to spawning rivers below major rim dams.
  9. Provide winter and spring flow pulses to stimulate juvenile emigration and to provide floodplain rearing opportunities.
  10. Limit South Delta exports during late fall to spring peak emigration periods.

With so many factors potentially affecting salmon survival and production, it is hard to say which of these prescriptions will be most effective. We should focus on doing them all, at least in this plentiful water year (2017).

Ocean condition indicators 1999-2016. Source: see footnote 1.
Red = poor conditions. Green = good conditions. Yellow = intermediate conditions.

Enhancing Coleman Hatchery Salmon Contribution

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In a recent post I discussed ways to improve hatchery salmon smolt survival to increase coastal and river salmon populations devastated by recent droughts. This post is a follow-up addressing how to enhance the Coleman (Battle Creek) Hatchery1 contribution. Coleman produces nearly half of the Central Valley’s 30 million hatchery-produced salmon smolts. Three state hatcheries in the Valley (Feather, American, and Mokelumne) produce most of the other smolts. Survival of Coleman hatchery smolts released to the Sacramento River is markedly lower in dry years.2 Trucking smolts from the hatchery to the Bay increases survival and catch in fisheries, but at a cost of increased straying and low return rates of adults to the hatchery.

Of all these hatcheries, Coleman has the toughest challenge, because it is nearly 300 miles from the Golden Gate. While trucking smolts to the San Francisco Bay improves smolt survival and adult salmon population numbers available to fisheries, trucking from Coleman leads to low hatchery-return rates and excessive straying to other Valley rivers. Only about 50-100 adults per million smolts trucked to the Bay find their back to Coleman. In contrast, for each million smolts released at the hatchery, 400-500 return to Coleman to contribute eggs for the next generation.

One measure to increase smolt survival-contribution I suggested in past posts is barging smolts to the Golden Gate. Unlike trucking, barging allows some imprinting by smolts for their eventual return route back to the hatchery. Barging requires a medium to large sized vessel, which would still necessitate nearly 200 miles of trucking to barge-accessible locations on the lower Sacramento River. Barging may reduce straying while providing enhanced smolt survival to the Bay, although past trucking and release at Knights Landing in the lower river only marginally lowered the straying rate compared to Bay releases. A balance between overall survival and contribution to the fishery and returns to the hatchery is the challenge for fisheries managers. Barging from Knights Landing or Elkhorn boat ramps may provide more returns to the Sacramento River above the mouths of the Feather and American rivers than trucking releases to these locations or the Bay. Regardless, barging should provide substantially higher survival and returns to the upper river than river release of fish, especially in dry years. Barging test studies conducted by the Feather Hatchery program should be expanded to test potential benefits of Coleman salmon smolt barging.

Another measure that deserves testing is rearing Coleman fall-run fry off-site in Yolo Bypass rice fields. The higher survival and growth potential and earlier ocean entry of these smolts compared with smolts released at the hatchery, should increase the numbers of adult salmon available to the fisheries. Concerns include low returns to Coleman hatchery and straying of returning adults back to the Yolo Bypass. The State’s EcoRestore Program is planning fish passage improvement projects in the upper Bypass. Barging off-site-reared smolts to the Bay from nearby Knights Landing or Elkhorn boat ramp could potentially improve return rates to the hatchery and overall survival, especially in dry years

A third proven measure that is possibly more promising and readily implementable is improving downstream migration conditions for smolts released to the upper Sacramento River from the Coleman hatchery. Smolt survival and contribution to fisheries and adult returns to the hatchery are better when flow, turbidity, and water temperature conditions are good at the time of release and in the immediate weeks thereafter in the 200 miles downstream to the Bay. To a certain extent, the hatchery can time releases to river conditions (and does so when feasible). However, the timing of smolting and the whole rearing process necessitates a week 15-17 release window (late April to beginning of May). When conditions are optimal in these key weeks, survival and contribution rates of smolts released at Coleman are nearly as high as they are for smolts transported to the Bay. Such 1-3% survival (returns) would produce hundreds of thousands of adults, compared to just tens of thousands under poor conditions when there is just 0.2-0.5% survival (Table 1). A 3% survival would yield 360,000 adult salmon returns from 12 million hatchery smolts, as compared to only 12,000 returns under a 0.1% survival.

So what are good conditions in late April? Adequate stream flows are those necessary to meet existing water quality standards, water right permits requirements, and endangered species permit requirements in the upper 200 miles of river below Shasta Dam. Such prescriptions are basically minimum targets: keeping the upper river within the 56oF limit upstream of Red Bluff and the river downstream to the Delta at 68oF or less. These standards were put in place decades ago to protect beneficial uses, including salmon survival.

The problem is that these standards are both increasingly being ignored and violated, and are also proving inadequate in providing optimal smolt survival. Figure 1 shows that standards were violated at Red Bluff, even in 2017, a record water supply year. Figure 2 shows 2017 water temperatures at Wilkins Slough in the lower Sacramento River. Though water temperatures remained below 68oF (20oC) during the period shown, they reached above the 65oF (18oC) stress level for migrating juvenile salmon. Such high water temperatures place the smolts at much greater risk to predation.3 Even in this record water supply year, water was unnecessarily held in storage in Shasta Reservoir at the expense of Coleman and wild salmon smolt survival. When water contractor demands are low and Delta conditions are “in excess,” there is a tendency in all year types to maintain Shasta storage at the expense of lower river water temperature and Coleman smolt survival.

In addition to maintaining flows and water temperatures, a flow pulse through the lower river in the late April to early May period would likely improve survival. A flow pulse in drier years would provide higher transport rates, higher turbidity, and lower water temperatures, conditions that often occur in wetter, high survival years. A one week pulse that raised flows from the “dry” year 5000 cfs flow level to a 10,000 cfs level would use approximately 10,000 acre-ft per day, or about 70,000 acre-ft for a week. At Shasta Reservoir’s current storage level in excess of 4 million acre-ft, the water needed for a one week flow pulse would be less than 2% of the total storage for the year. Even for a multiyear drought year like 2015, the amount needed would be only 3 to 4% of total annual storage. While drought year pulses would need to be weighed against losses to the Shasta coldwater pool, a 1% improvement in dry-year survival would add 120,000 adult salmon from the 12 million smolts produced by the Colman hatchery. For a dry year or drought year sequence, the increase could be over 100% over current survival rates, and could allow a salmon fishing season when there might otherwise be none.

In summary, the salmon fishery collapses that occurred as a consequence of the 2007-2009 and 2012-2015 droughts could have been at least partially alleviated by improving survival of smolts produced at the Coleman hatchery. Compliance with spring water temperature standards in the lower Sacramento River would help greatly. When water supplies are adequate, spring flow pulses should be considered. Barging Coleman smolts to the Bay and off-site rearing in lower river floodplain habitats are additional measures to test in order to increase Coleman hatchery smolt survival and contributions to ocean and river fisheries.

Table 1. Survival (return) rates of Coleman hatchery fall run Chinook salmon release groups for a range of year types.
Source of survival data: http://www.rmpc.org.

Water Year Week 15-17 Conditions Smolt Survival4
1997 Wet Year Lower River conditions were deteriorating in April with flows falling from 7000 to 5000 cfs and water temperatures rising from 59oF (15oC) to 65oF (18oC). Week 15 – 0.8%
Week 16 – 0.3%
Week 17 – 0.2%
1998 Wet Year Lower River conditions were near optimal with 18,000 cfs flow and water temperature of 15oC. Week 17 – 0.9%
2002 Dry Year Lower River conditions degraded gradually from week 15 to week 17).  Flows in lower river fell from near 10,000 cfs to less than 5000 cfs during April.  Though water temperatures remained below 68oF (20 o C) during the period, they often reached above the 65oF (18 oC) stressful level for migrating juvenile salmon. Week 16 – 0.8%
Week 17 – 0.6%
2007 Critical Dry Year Lower River conditions were poor in weeks 16-17 with flows of 4000-5000 cfs and water temperatures of 19-21oC. Week 16 – 0.01%5
2008 Critical Dry Year Lower River conditions were poor with flows of 5000 cfs and water temperatures 16oC to 18oC in weeks 16-17, but reaching 20-22oC in week 18. Week 16 – 0.1%
Week 17 – 0.1%
2009 Critical Dry Year Lower River flow decreased from 7000 cfs to 5000 cfs in weeks 15-16, while water temperature rose from 15oC to 20oC.  Flow pulsed to 10,000 cfs in week 17 dropping water temperature to 15oC. Week 15 – 0.5%
Week 16 – 0.9%
2011 Wet Year Lower river flows in April were dropping sharply from 16,000 to 8,000 cfs, with water temperature rising from 15oC to 18oC. Week 15 – 2.2%
Week 16 – 1.5%
Week 17 – 1.2%

Figure 1. May 2017 flow and water temperature conditions in upper Sacramento River. Source: CDEC.

Figure 2. May 2017 water temperature in lower Sacramento River at Wilkins Slough. Source: CDEC.

  1. The Coleman Hatchery near Redding on Battle Creek is operated by the US Fish and Wildlife Service. The hatchery operates under the Central Valley Project as mitigation for Shasta Dam on the upper Sacramento River ↩
  2. http://calsport.org/fisheriesblog/?p=1703 ↩
  3. http://calsport.org/fisheriesblog/?p=878 ↩
  4. Survival rate is defined as percent of smolts that were subsequently collected as adults in fisheries, spawning surveys, and at Central Valley hatcheries. Average rate of multiple groups is shown. ↩
  5. Poor ocean conditions in 2007-2009 likely contributed to poor survival. ↩

Improving Hatchery Salmon Survival

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One way to effectively increase the California coastal salmon population is to increase survival of Chinook salmon smolts released by the three large Sacramento Valley hatcheries. These three hatcheries produce nearly 30 million fall-run smolts a year and account for 70-90% of California’s ocean and river fishery catch. A one percent smolt survival leads to 300,000 adult returns to the fisheries and escapement to spawning rivers. Doubling survival to two percent would increase returns to 600,000 adults. With survival at or below one-half percent in recent drought years, returns have fallen to near 100,000.1

How can we get survival back to one or even two percent or higher? Fortunately at least a quarter of the smolts are tagged to allow estimates of their survival and contributions to fisheries and escapement back to spawning rivers. Survival estimates are now available for hatchery smolts released up to 2013. Figures 1-3 show a summary of survival from the three largest hatcheries for salmon brood years 2008-2012 (smolt releases from 2009-2013). I drew the following conclusions from the figures:

  1. Releasing smolts in the spring of drought years in the rivers near the hatcheries provides only about a half percent survival in drought years (release years 2009 and 2013). Survival improves to 1-3 % in wetter years (release years 2010 and 2011), likely a consequence of better transport flows, lower water temperatures, and lower predation because of higher turbidity.
  2. Poor ocean survival (2008-2009, and 2014-2015) likely contributes to poor survival (percent returns) for those brood years rearing in the ocean under poor conditions.
  3. Transporting the salmon smolts via truck to San Francisco Bay for release into acclimation pens markedly increases survival in dry and wetter years into the 1-3% range. The benefit appears smaller in the wetter years, but remains significant and substantial. The Feather and American state hatcheries continue transporting the bulk of their smolts in recent years, while the federal Coleman hatchery has greatly reduced the practice because of apparent higher straying rates.
  4. The program of releasing Feather smolts to coastal bay pens sharply increases returns to coastal fisheries. However, the threat of these fish straying to coastal streams with different genetic stocks now limits this practice.
  5. Lastly, barging fish from near their hatcheries to the Bay shows much promise. Barging may triple survival in drier years when survival is one percent or less, and may reduce straying. A multiyear study of barging is currently underway.

In conclusion, adult salmon stocks in coastal waters continue to benefit from transporting smolts to Bay net pens. Further benefits may derive from barging the smolts 100 to 200 miles to the Bay. Potential benefits of barging over trucking include higher survival and reduced straying. Release of hatchery smolts directly to Sacramento Valley rivers near the hatcheries provides minimal survival especially in drier years. Increasing survival factors like augmenting flow releases from reservoirs at the time of river hatchery releases may improve survival, but trucking and barging appear necessary to keep ocean and river fisheries afloat in the short term.

Figure 1. Feather River hatchery fall-run salmon return rates by release method for brood years 2008-2012 (release years 2009-2013). Source of data: http://www.rmpc.org/

Figure 2. American River hatchery fall-run salmon return rates by release method for brood years 2008-2012 (release years 2009-2013). Source of data: http://www.rmpc.org/

Figure 3. Sacramento River (Coleman) hatchery fall-run salmon return rates by release method for brood years 2008-2012 (release years 2009-2013). Source of data: http://www.rmpc.org/

American River Salmon Hatchery Begins Taking Salmon

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California Department of Fish and Wildlife has announced that it opened the American River Nimbus Hatchery ladder on Nov 2.  At the same time, the feds have managed to cool down the river to allow salmon in the river to also begin spawning (Figure 1).  The Bureau of Reclamation cooled the river by opening lower level outlets of Folsom Dam for a portion of the day beginning in late October (Figures 2 and 3).  This allowed the release of  colder water from deep in the reservoir into the Nimbus regulating reservoir directly downstream of Folsom Reservoir.  There, the cold water mixed with warmer reservoir waters before discharge to the lower American River.

The real story here is that the feds had to wait until November to cool water both in the river, and in the Nimbus Fish Hatchery just downstream of Nimbus Dam.  The supply of cold water in Folsom Reservoir is limited this fall because of excessive releases of stored water to the Delta this past summer (see prior post).  The summer shrinkage of Folsom’s cold-water pool subjected the salmon that entered the lower American River in September and October to a month or more of stress from warm water.  That stress will likely reduce survival of pre-spawn and spawning salmon, diminish their success in spawning, and make many of eggs and embryos spawned in the river unviable.

Figure 1. Water temperature below Nimbus Dam on the lower American River near the Nimbus Hatchery Oct 4 – Nov 2, 2016. Red line denotes safe water temperature for holding and spawning salmon, and salmon egg survival.

Figure 1. Water temperature below Nimbus Dam on the lower American River near the Nimbus Hatchery Oct 4 – Nov 2, 2016. Red line denotes safe water temperature for holding and spawning salmon, and salmon egg survival.

Figure 2. Temperature of the water released from Folsom Dam Oct 21 – Nov 2, 2016. Red circles show the release of water from Folsom’s cold-water pool.

Figure 2. Temperature of the water released from Folsom Dam Oct 21 – Nov 2, 2016. Red circles show the release of water from Folsom’s cold-water pool.

Figure 3. Flow releases from Folsom Dam. Red circles depict flow releases of cold water from lower level outlet of dam Oct 21 – Nov 2, 2016.

Figure 3. Flow releases from Folsom Dam. Red circles depict flow releases of cold water from lower level outlet of dam Oct 21 – Nov 2, 2016.