The prognosis for winter-run Chinook salmon is not good following very poor survival of the 2014 and 2015 spawns in the Sacramento River below Shasta Dam. The run had been recovering after the 2007-2009 drought (Figure 1). However, year class production suffered in the 2012-2015 drought, culminating with the year class (spawn) failures in 2014 and 2015 (Figure 2) caused by egg stranding and high water temperatures. Run size and juvenile production/survival estimates for 2016 are as yet incomplete, but production of juveniles as estimated from Red Bluff rotary screw trap data indicates some improvement over 2014-2015. The somewhat higher number of recruits produced in 2013 likely boosted the spawning run in 2016.
With water year 2017 starting out as a wet year with considerable flooding, conditions for the emigration of the 2016 year class should be optimal. If wet conditions persist, spawning and rearing this spring and summer for the 2017 year class should also be optimal. Planned release of 600,000 winter-run hatchery smolts in the coming weeks coincident to high Sacramento River flows also bodes well for the 2016 spawn and the future 2019 run. However, the prognosis for the 2017 and 2018 runs remains in doubt because of the above-mentioned 2014 and 2015 year class failures.
Additional insight into the future is possible by taking a closer look at the population’s spawner-recruit relationship that I prepared for the past four decades (Figure 3). Recruitment appears to be a function of both the number of spawners three years prior to any given year and environmental conditions between spawning and emigration in a given year. (Other factors such as ocean conditions may also add to variability in the data.) The recruits-per-spawner ratio is higher three years after wet years than three years after dry years. The runs in 2017 and 2018 are likely to be severely depressed because of extremely poor 2014 and 2015 recruitment, and may possibly be as low as those produced after the 1987-91 drought (only 100-200 wild spawners).
For further reading on winter-run status see:
- http://deltacouncil.ca.gov/sites/default/files/2015/11/Vogel%20White%20Paper-%20Potential%20effects%20of%20CVP %20Ops%20on%20winter%20run%20Chinook%20egg%20incubation%202015.pdf
The prognosis for splittail was not good in 2015 after four years of drought and little recruitment since 2011. The below-normal water year in 2016, with its limited winter flooding, brought no apparent recovery in the Fall Midwater Trawl Index (Figure 1). Summer salvage (Figure 2) indicated that there was some production in 2016, although salvage was two orders of magnitude lower than the previous normal water year 2010 (Figure 3) and three orders of magnitude less than the previous wet water year 2011 (Figure 4).
If water year 2017 were to continue on its current trajectory and become a wet year with widespread flooding, conditions for splittail spawning and rearing this winter and spring would be optimal. A positive response in salvage, Fall Midwater Trawl Survey, and FWS Seine Survey would indicate some form of recovery in the population. However, a lack of response on the order of that which occurred in 2011 would be a signal that the population is in dire straits and at risk of recruitment failure and eventual extinction. In the absence of a 2011-magnitude response in the next wet year, the fisheries agencies should conduct a comprehensive review to evaluate whether to re-list splittail under the federal and state endangered species acts.
Figure 1. Splittail Fall Midwater Trawl Survey Index 1967-2016. (Data Source)
Figure 2. Splittail salvage in 2016. Export rate for federal and state pumping plants. (Source)
Figure 3. Splittail salvage in 2010. Export rate for federal and state pumping plants. (Source)
Figure 4. Splittail salvage in 2011. Export rate for federal and state pumping plants. (Source)
The prognosis for stripers was not good in 2015 after four years of drought. The normal water year in 2016 brought only minor improvement in recruitment of juveniles into the population, but recruitment remains near record lows (Figures 1-3). The wetter 2016 started with higher juvenile production, but that stalled by late spring. Striped bass salvage at south Delta export facilities showed typical patterns, with about 10% of the numbers salvaged in year 2000 and two primary peaks in salvage – late spring/early summer and late fall (Figure 4).
The Fall Recruitment Index of juveniles into the population as derived from the Fall Midwater Trawl Survey (Figure 2) compared with the prior Summer Townet Survey (Figure 1) indicates a strong positive relationship (Figure 5). The year class strength is very much dependent on the number of young starting the summer, which in turn is likely related to the number of eggs laid in spring and subsequent survival of larvae hatched to the early summer juvenile stage as measured in the Summer Townet Survey. Subsequent survival to the fall appears related to summer habitat conditions, for which a good indicator is Delta outflow. High relative survival to fall in 1998 and 2006 (labeled blue in Figure 5) is likely due to these summers’ higher Delta outflow (Figure 6) and related Delta conditions including export levels (Figure 4). The 2010 and 2016 fall indices were likely suppressed by low outflow, high exports, and resulting poor in-Delta survival, indicated by high salvage numbers. Likewise summer and fall indices in drought years 2007, 2014, and 2015 were likely depressed (Figure 5) by these same factors.
The above patterns and observations are very important because the striped bass remain an important indicator of Bay-Delta Estuary ecological health.
Figure 1. Striped bass Summer Townet Survey Index 1959-2016. (Data Source)
Figure 2. Striped bass Fall Midwater Trawl Survey Index 1967-2016. (Data Source)
Figure 3. Striped bass Fall Midwater Trawl Survey Index 2000-2016. (Same source as Figure 2)
Figure 4. Striped bass salvage at south Delta fish facilities in 2016. Export rate is shown as acre-feet (~2 times rate in cfs). (Data Source)
Figure 5. Striped bass Fall Midwater Trawl Survey Index (log10[index+1]) versus prior Summer Townet Index (log10). Select years labeled, with color of number showing year type: blue=wet, green=normal, and red=critically dry.
Figure 6. June through August Delta outflow in 1998, 2006, and 2010.
The conflict continues between the Smelt Working Group (SWG) and the designated protector of the Delta smelt, the US Fish and Wildlife Service (FWS), over the amount of Delta exports allowed under existing Delta conditions. The SWG recommends exports of no more than 2000 cfs, while the FWS continues to allow exports of 5000-6000 cfs (about half capacity), contrary to the rules for Delta exports in its own smelt biological opinion. The SWG notes that adult smelt continue to be captured in trawls in the central Delta (in surprising numbers), where smelt are at high risk of being drawn to the south Delta pumping plants or of eventually spawning in the central Delta where their offspring will be vulnerable to the export pumps. The FWS is committed to allowing moderate exports as long as no adults are captured at the pumping plants’ fish salvage facilities (which would indicate it is too late to do anything other than to shut down the pumps). The National Marine Fisheries Service limits exports to the present 5000-6000 cfs level as of January 1, consistent with rules in its own biological opinion to protect juvenile salmon migrating down the Sacramento River.
Despite high Sacramento River inflows into the Delta of 30,000 to 50,000 cfs in the past two weeks, the smelt move from the Bay into the Delta by surfing the tides – that is, by moving upstream on incoming tides. Flood tide velocities shown in Figure 1 indicate the adult smelt can readily “surf” into the Delta until they come up against the strong flows of the Sacramento River and its inflow channels that overwhelm the tidal flows. In the south Delta, where limited flow has been coming down the San Joaquin River, export pumping plants accentuate the negative flood tide velocities and reduce ebb tide velocities. This further increases the risk that adult smelt will be drawn to the south Delta. Only time will tell if this risky FWS strategy protects the endangered Delta smelt during this potential comeback year.
Figure 1. Flood tide channel current velocities in feet/second in early January 2017. Arrows depict current direction on flood tides. Sacramento River net downstream flow was 30,000-50,000 cfs, which overwhelmed the flood tide. Light blue dots are flow gaging stations. Basemap source with gaging stations is DWR/CDEC.
The longfin smelt population in the Bay-Delta reached a near record low index in 2016 (Figures 1 and 2). The index was 7, slightly higher than the record low index of 4 in fall 2015. There is a strong positive spawner (fall index two years prior) to recruitment (fall index) relationship (Figure 3). Recruitment is strongly related to the number of spawners (likely the number of eggs spawned). Recruits-per-spawner is also strongly influenced by wet or dry year conditions; in other words, first-year survival is higher in wetter years. The poor fall 2015 and 2016 indices indicate that recruitment in 2017 and 2018 is likely to continue at record low levels. Adult longfin (presumably some two-year-old spawners) were collected in the Bay trawl survey in December 2016. Mid-January 2017 larval smelt surveys will be the first indication of recruitment into the population in 2017. Water year 2017 has been a wet year to date, so some positive response in recruitment could potentially occur.
We will be keeping a close look at longfin recruitment in 2017, especially with new less stringent export restrictions mandated in recent legislation for the implementation of the two federal biological opinions that apply to Delta water project operations. So far, no adult longfin have been collected in salvage at the south Delta export facilities.
Figure 1. Longfin smelt Fall Midwater Trawl indices 1967-2016. Source: CDFW.
Figure 2. Longfin smelt Fall Midwater Trawl indices 2000-2016. (Note: 2007=13; 2015=4; 2016=7) Source: CDFW.
Figure 3. Longfin smelt Fall Midwater Trawl Index (Recruits) vs two-year-prior index (Spawners), log10 scales. Wet years are blue labelled; dry years are red labelled.