Category Archives: Sturgeon

Sturgeon and the Drought

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The State Water Board’s weakening of the water temperature standards in the Sacramento River below Shasta at the request of Reclamation and concurrence by NMFS this late spring and early summer has likely led to excessive take during this spawning season of listed Green Sturgeon, increasing their risk of their extinction. Lower flows and higher temperatures in the Sacramento River’s Green Sturgeon spawning reach from Anderson (RM 280) to Hamilton City (RM 200) has likely resulted in a substantial mortality of eggs and larval Green Sturgeon, as well as White Sturgeon, during and following their May-June spawning season.

Water temperatures below Red Bluff (RM 240) exceeded the upper thermal optimum for Green Sturgeon embryos (17-18°C, 62-65°F1) from late spring to early summer 2015 (Figure 1), but rarely in 2012, the first year of the present drought (Figure 2), when standards were not weakened. Water temperatures exceeded 62°F nearly to Anderson at times this summer (Balls Ferry and Jelly’s Ferry). Approximately half the spawning reach has been severely degraded by warm water from weakened standards (Figure 3). Lower flows and higher water temperatures have likely led to earlier spawning and more concentrated spawning in the upper end of the spawning reach. The river below Hamilton City, where eggs and fry drift and many young rear, is degraded with high water temperature even above 100% lethal levels (23°C, 73°°F) at Wilkins Slough (RM 120) (Figure 4). In 2012, when standards were not weakened, conditions at Wilkins Slough were much better and near optimum (Figure 5). However, even in 2012 (the first year of the present drought cycle) Green Sturgeon tended to spawn further upstream in the spawning reach than in previous years2 because of lower river flows and/or higher water temperatures.

What applies to Green Sturgeon also applies to the non-listed White Sturgeon, whose spawning and rearing requirements, timing, and locations are similar to those of the Green Sturgeon3. Concerns for the White Sturgeon are ever increasing4. The risks extend to adult White Sturgeon, which have undergone a die-off in the Columbia River under similar circumstances5.

Figure 1

Figure 1. Water temperatures at Red Bluff on Sacramento River late spring and early summer 2015. (Source: CDEC)

figure 2

Figure 2. Water temperatures at Red Bluff on Sacramento River late spring and early summer 2012. (Source: CDEC)

Figure 3

Figure 3. Green Sturgeon spawning reach in the Sacramento River (green highlight). Reach degraded by high water temperature in 2015 (red highlight).

Figure 4

Figure 4. Water temperatures at Wilkins Slough (RM 120) on Sacramento River late spring and early summer 2015. (Source: USGS)

Figure 5

Figure 5. Water temperatures at Wilkins Slough (RM 120) on Sacramento River late spring and early summer 2012. (Source: USGS)

  1. “Water temperature for spawning and egg incubation is near optimal (15oC/ 59oF)) from RBDD upriver during the spawning season. Below RBDD, water quality, in terms of water temperature, gradually degrades and eventually exceeds the thermal tolerance level for egg incubation, when egg hatching success decreases and malformations in embryos increase above 17 oC/62 oF, at Hamilton City”. (NMFS OCAP Biological Opinion p276) ↩
  2. William R. Poytress, Joshua J. Gruber, Joel P. Van Eenennaam & Mark Gard (2015) Spatial and Temporal Distribution of Spawning Events and Habitat Characteristics of Sacramento River Green Sturgeon, Transactions of the American Fisheries Society, 144:6, 1129-1142, DOI: 10.1080/00028487.2015.1069213 ↩
  3. White Sturgeon generally spawn lower in the river than Green Sturgeon. ↩
  4. http://www.scout.com/outdoors/fish-sniffer/story/1563429-ca-dfw-considers-slashing-sturgeon-fishing
    https://cdfgnews.wordpress.com/2015/08/11/responsible-angling-practices-help-conserve-sturgeon-populations/
    ↩
  5. http://www.cbbulletin.com/434540.aspx ↩

Knights Landing Outfall Gates New Screens – Only a Start

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A SacBee article on October 22, 20151 describes the nearly completed Knights Landing Outfall Gates (KLOG or Outfall Gates) screening project on the Sacramento River: “local, state and federal officials are close to completing a $2.5 million project that will block an entrance wayward salmon use to get into the Colusa Basin Drain”. The operative word here is “an”, because the other entrance, and by far the more important, is the Knights Landing Ridge Cut (KLRC or Ridge Cut) outlet into the upper Yolo Bypass (Map 1).

Upstream-migrating Winter Run Chinook Salmon bound for spawning grounds below Shasta Dam near Redding in the Sacramento River can be attracted into irrigation and stormwater drainage system outfalls and eventually lost. The two largest outfalls are the Yolo and Sutter bypasses (see my previous blog on the bypass attraction – http://calsport.org/fisheriesblog/?p=421 ). Of lesser importance are a series of agricultural outfalls from low-lying basins adjacent to the Sacramento River. Chief among these are the Knights Landing Outfall Gates, which drain the Colusa Basin on the west side of the Sacramento River Valley.

The new screens on Outfall Gates will ensure that no salmon leave the river for the basin through the gates. But that is not the big problem. The Colusa Basin Drain (CBD or Drain) is also a stormwater drain that can flow mightily in winter storms even in drought years such as 2013-2015 (Charts 1 and 2). When stormwater-driven high flows in the Drain occur, the Outfall Gates’ outlet is usually closed because the river is higher than the gates during storm runoff. Under these high flows, water in the Drain is forced down the Knights Landing Ridge Cut into the upper Yolo Bypass (see Map 1).

Storm runoff that passes through the Ridge Cut into the Yolo Bypass attracts many salmon, steelhead, and sturgeon into the Drain and to their eventual demise in the dead-end Colusa Basin. Storm flow to the Yolo Bypass reaches 4000-6000 cfs in drought years, while non-storm flows through the Outfall Gates are usually only several hundred cfs (Charts 1 and 2). Flows leaving the Yolo Bypass and entering the Delta at Cache Slough (Map 2) attract many salmon, steelhead, and sturgeon moving through the Delta. During floods, the Sacramento River spills into the Yolo Bypass, adding even more attraction flows through Cache Slough. With limited passage options past the Fremont Weir at the upper end of the Yolo Bypass (Map 1 or 2), many of fish moving up the Yolo Bypass are attracted to and migrate up the Ridge Cut.

In short, the Knights Landing Ridge Cut outlet also needs to be blocked to keep fish from migrating into the Colusa Basin and being lost. The threat is serious not only to Winter Run Chinook, but also to Fall Run, Late Fall Run and Spring Run Chinook, as well as Steelhead, Green Sturgeon and White Sturgeon. Fish passage facilities at Fremont Weir are also needed so that adult fish that migrate up the Yolo Bypass are not stranded in the Bypass.

Map 1

Map 1. Location of Knights Landing Outfall Gates (KLOG) on Sacramento River and Knights Landing Ridge Cut (KLRC) outlet in the Yolo Bypass near Knights Landing, CA. Red arrows point out routes taken by salmon into the Colusa Basin.

Chart 1

Chart 1. Flow in the Colusa Basin Drain Nov 2013 through May 2014. Red line depicts flow when KLOG were closed due to high Sacramento River stage. (At flows above about 900 cfs in the CBD the KLOG were closed and flow diverted to Yolo Bypass via KLRC.)

Chart 2

Chart 2. Flow in the Colusa Basin Drain Nov 2014 through May 2015. Red line depicts flow when KLOG were closed due to high Sacramento River stage.

Map 2

Map 2. Route salmon take from the Delta via Cache Slough up the Yolo Bypass when attraction flows are input from either the Knights Landing Ridge Cut or the Fremont Weir.

Loss of Salmon in the Sacramento River Floodplain

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The loss of juvenile and adult salmon in the Sacramento River floodplain has been a problem for many decades. The problem is largely the result of the construction of dams, agricultural drains, and flood control systems. The problem is acute, and although well documented and quite obvious, little has been done to resolve it. The fixes are not cheap and no one wants to get stuck paying for them. In addition, potential fixes have been hoarded as potential mitigations for large public works projects like the Bay Delta Conservation Plan and its associated Delta Tunnels.

The Problem

Figure 1 is a map of the Sacramento Valley with arrows showing some of the major locations of the problem. Much of the problem is the result of limitation or blockage of fish passage; another major factor is stranding. Adult salmon, sturgeon, and steelhead migrating up the Sacramento River become attracted to the high volumes of Sacramento water exiting the Sutter and Yolo Bypasses (adult fish movement is shown by red arrows in Figure 1), only to be blocked at the high weirs at the upstream end of the bypasses (Figures 2 and 3). Even modest bypass flows in drought years can cause attraction and subsequent mortality (Figure 4).

Young salmon emigrating downstream from upriver spawning grounds pass into the bypasses (green arrows in Figure 1) and adjacent basins in huge numbers. Many become stranded and lost when flows and water levels decline when weirs quit spilling (the river can drop ten feet overnight and quickly cease spilling into bypasses).

Landowners Seek Solution

In one of the areas, the Yolo Bypass, local landowners and stakeholders are seeking a solution. They are addressing three critical issues:

  1. Blockage of upstream migrating fish behind the Fremont Weir at the head of the Bypass.
  2. Blocked fish migrating to their deaths into the Colusa Basin from the Bypass via the Knights Landing Ridge Cut1. Adult migrants are also attracted directly to Colusa Basin Drain outlet even when Fremont Weir does not spill.
  3. Increasing survival of young salmon spilled into the Yolo Bypass by augmenting flows and improving habitats and habitat connectivity.

The first issue often occurs each time the weir spills at flood stage (generally one in three years, although it has not spilled significantly since 2006 because of drought). The bandaid treatment is shown in Figure 2. Stakeholders have advocated a short-term solution for passing fish via a “small notch” in the Fremont Weir to pass fish over the weir into the river; however, long-term agency plans call for a more contentious “large notch” in the weir.

The second issue requires the opposite solution, placing a fish-blocking weir at the outlet of the Knights Landing Ridge Cut to stop adult salmon, sturgeon, and steelhead from migrating upstream into the Colusa Basin. Landowners are working with the California Department of Water Resources and Reclamation toward building such a weir. For now the bandaid is a fish trap and fish rescues such as that shown in Figure 2.

The third issue can be resolved by engineering the bypass floodplain to provide better habitat and connectivity for the salmon including high and longer-sustained flows from the Fremont Weir (via a “notch”). Local landowners have developed an array of actions to provide habitat and connectivity.

In my experience, placing leadership and responsibility for developing and implementing actions in the hands of local stakeholders has worked best to help save fish. “Locals” can be surprisingly adept at coming up with viable solutions to fisheries problems.

Map of Sacramento Valley showing levees and flood control system weirs and bypasses

Figure 1. Map of Sacramento Valley showing levees and flood control system weirs and bypasses. Gray area agricultural basins are generally below the elevation of the river and bypasses. The flood control system was initially designed to convey flood water and historic foothill mining debris through the Valley. Adult salmon (as well as sturgeon and steelhead) are attracted to the high flows entering, passing through, and exiting the Sutter and Yolo Bypasses (such adult migration is shown with red arrows). Many cannot successfully complete their passage either becoming lost or blocked at the upstream end by weirs (located at the blunt end of the green arrows). Many young salmon become stranded in the basins and bypasses after entering in spill over weirs during floods. (Map source: http://baydeltaconservationplan.com/Libraries/Dynamic_Document_Library/Fact_Sheet_-_Sac_River_System_Weirs_and_Relief_Structures.sflb.ashx )

Figure 2. Sturgeon being rescued below a Sacramento River bypass weir

Figure 2. Sturgeon being rescued below a Sacramento River bypass weir

Moulton Weir 1997

High storm flows in late December 2014 into the Yolo Bypass from the Knights Landing Ridge Cut attracted many salmon to the northern end of the Bypass

Figure 4. High storm flows in late December 2014 into the Yolo Bypass from the Knights Landing Ridge Cut attracted many salmon to the northern end of the Bypass. When storm flows receded after several days, hundreds of adult salmon became stranded in winter-fallow fields that had been flooded. Many more salmon likely passed successfully into the Colusa Basin drain system only to find no route to spawning grounds in the upper Valley.