Do Klamath Basin Farmers Jeopardize Endangered Orcas? (revised 15 May 2026)

What the Best Available Science Shows — and the Question Federal Agencies Have Never Been Asked

For more than two decades, advocacy groups have argued that water deliveries to Klamath Reclamation Project farmers in Southern Oregon and Northern California are driving the decline of the endangered Southern Resident Killer Whales (SRKWs). Earthjustice’s Klamath case page, for example, describes the Southern Residents as a population that “depend[s] on Klamath River Chinook Salmon as prey” — and uses that framing to seek restrictions on water deliveries to family farms.

This article walks through what the peer-reviewed science actually shows about that claim, what the federal government has and has not concluded, an important question that federal agencies have never been asked to answer under current river conditions, the most recent peer-reviewed research on what is actually driving SRKW decline, and the logical contradiction in the federal record that, once you see it, cannot be unseen.

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Who Are the Southern Resident Killer Whales?

The Southern Residents are a small, endangered population of fish-eating orcas listed under the U.S. Endangered Species Act in 2005. They consist of three family groups, called pods — J, K, and L.

As of the December 14, 2025 update from the Center for Whale Research, the population totaled 76 individuals: 27 in J pod, 15 in K pod, and 34 in L pod. The July 2025 official summer census counted 74. Recent calves account for the difference.

Here is what the peer-reviewed dietary research says about each pod and the Klamath:

• J Pod (27 whales): essentially 0% Klamath Chinook in diet. J pod spends most of its time in the Salish Sea and rarely travels south of the Columbia River. The peer-reviewed genetic analysis by Hanson et al. 2021 did not detect Klamath-origin Chinook in any J pod prey samples.
• K Pod (15 whales): likely very low or near-zero Klamath contribution. K pod’s documented range only marginally overlaps with the ocean waters where adult Klamath Chinook concentrate.
• L Pod (34 whales): the 2.2% Klamath figure most likely concentrates here. L pod ranges more widely along the outer coast in fall and winter and can be present near the mouth of the Klamath River seasonally — while also feeding on Chinook from many other river systems during that time.

Putting those numbers together: the Klamath dietary contribution at the 2.2% level effectively applies to 34 of 76 whales — about 45 percent of the SRKW population. The other 55 percent show essentially zero Klamath (including Trinity River) in their diet.

Sources: NOAA Fisheries Killer Whale species pages; Center for Whale Research 2025 census; Hanson et al. 2021 (peer-reviewed, PLoS ONE).

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The Contradiction in the Federal Record

Before walking through the science, one observation has to be made plainly. The federal record contains an inconsistency that no one in the regulatory or advocacy community has yet been asked to explain.

What the federal government accepted in 2022 as “less than significant” for SRKW:

In August 2022, the Federal Energy Regulatory Commission published its Final Environmental Impact Statement for the Lower Klamath Project decommissioning — the federal review that approved dam removal. In that document, FERC accepted, in advance, the following short-term harms from the drawdown:

• Significant, unavoidable, adverse effects on all life stages of anadromous fish in the lower Klamath River during the drawdown year — Chinook, coho, steelhead, and Pacific lamprey
• Significant fine sediment deposition burying spawning gravel
• Significant drops in dissolved oxygen
• Death of freshwater mussels
• Adverse effects on federally threatened Southern DPS eulachon
• Adverse effects on federally endangered Lost River and shortnose suckers
• Elimination of Iron Gate Hatchery production with a forecast “short-term reduction in adult returns”
• Adverse effects on bottom-dwelling invertebrates throughout the lower river

These were not theoretical. The 2024 brood year was largely lost. The lower-river spawning grounds below the former dams were buried in fine sediment. FERC predicted these things in 2022, and they happened in 2024. The federal record accepted these adverse effects in advance.

And FERC concluded these dramatic, certain, federally-acknowledged salmon losses would have only a “less than significant” effect on Southern Resident Killer Whales — because, in FERC’s own words, “the Klamath River contributes a small number of Chinook salmon to the Southern Resident killer whale prey base.”

What the same federal regulatory system continues to treat as a potential SRKW jeopardy concern:

Klamath Reclamation Project operations — which:

• Sit more than 250 river miles upstream of the ocean and the SRKW foraging zone
• Operate entirely above the reaches where most salmon historically lived (natural geological barriers in the Project area were significant obstacles to salmon for thousands of years before any dam was built; some evidence suggests certain very hardy Chinook and Steelhead occasionally passed under specific conditions, but the area was not consistently accessible)
• Return a substantial share of diverted water back to the system
• In wet years, add stored Upper Klamath Lake water to the river when natural flows would otherwise be lower
• In average years, have approximately a neutral net effect on downstream volumes
• In dry years, divert only minimal water above what natural conditions would have produced, with the mainstem remaining wet throughout
• Continued delivering water throughout 2024 and 2025 — during which the basin produced 51,277 adult fall Chinook at 205% of preseason forecast

Biology cannot make these two things consistent. Either the Klamath’s contribution to SRKW diet is too small to matter (FERC’s finding), or it is large enough that upper-basin water management moves the SRKW needle. It cannot be both.

If FERC was correct that a ~2.3% Klamath contribution means even catastrophic short-term salmon losses produce only a “less than significant” SRKW effect, then ordinary year-to-year variation in upper-basin water deliveries — which are smaller, more reversible, and which leave the mainstem wet — cannot rise to the level of an SRKW jeopardy issue. The dose-response relationship FERC established applies to every subsequent question about how Klamath salmon production affects SRKW.

The fact that federal regulatory practice continues to treat Klamath Project operations as a continuing SRKW concern, while the same agency that approved dam removal concluded the basin’s Chinook contribution is too small to materially affect SRKW, is not a biological conclusion. It is an institutional one.

The rest of this article walks through the science that supports this observation.

Source: FERC, Final Environmental Impact Statement for Hydropower License Surrender and Decommissioning, Lower Klamath Project (P-14803-001), August 2022, FERC/EIS-0313F, Table ES-2 (main document PDF; Appendices).

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FERC’s Own Words on SRKW

Here is FERC’s language verbatim from the Final EIS:

“Klamath River salmon only contribute approximately 2.3 percent of the prey base for Southern Resident killer whales.”

“Because the Klamath River contributes a small number of Chinook salmon to the Southern Resident killer whale prey base, adverse effects on salmon from elevated [suspended sediment concentrations] would have a less than significant effect on Southern Resident killer whales.”

This finding cuts both ways logically. You cannot argue that dam removal benefits SRKW by helping Klamath salmon — FERC said the benefit is “less than significant” — while simultaneously arguing that Klamath water deliveries, which actually add water to the river above natural conditions in many years, threaten SRKW by hurting Klamath salmon. Either Klamath Chinook matters to SRKW survival or it doesn’t. The federal record says it doesn’t.

FERC’s quantitative estimate of ~2.3% is also essentially identical to the peer-reviewed Hanson et al. 2021 figure of 2.2% ± 2.3% — they reinforce each other.

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What the Southern Residents Actually Eat: The Peer-Reviewed Dietary Science

This section relies on peer-reviewed genetic research that identifies the specific salmon stocks SRKWs consume.

The lead study is Hanson et al. 2021 in PLoS ONE — NOAA scientists used DNA from prey remains and from feces to identify which Chinook stocks SRKWs were eating throughout their range, in fall, winter, and spring. (Summer diet in the Salish Sea was characterized separately in another peer-reviewed paper, Ford et al. 2016 in PLoS ONE, which showed Fraser River stocks dominate.) FERC relied on this peer-reviewed dietary literature to arrive at its ~2.3% Klamath figure.

The peer-reviewed findings most relevant to the Klamath question:

1. Klamath-stock Chinook appeared in SRKW diet only in K and L pods, only in outer coast waters, and only during mid-winter to early spring. Sample size was 33 prey-remains samples. The estimated contribution was 2.2% ± 2.3% standard error.

That standard error is larger than the estimate itself. In plain English, that means the Klamath contribution is so small that, statistically, it can’t be reliably distinguished from zero. The data are real, but the signal is tiny.

2. The dominant Chinook stocks in K and L pod outer-coast diet during that same period:

Peer-reviewed source: Hanson et al. 2021, Table 2.

3. In Puget Sound during fall and early winter (a separate sample set of 20 prey items), South Puget Sound stocks (61.9%) and Lower Fraser River stocks (10.0%) dominated. Klamath stocks were not detected at all.

4. In summer months in the Salish Sea, Fraser River stocks dominated SRKW diet. No meaningful Klamath contribution (Ford et al. 2016, peer-reviewed).

The peer-reviewed literature does not separate the contribution of mainstem Klamath versus Trinity River Chinook to SRKW diet. The “Klamath R.” category in Hanson et al. 2021 covers the basin as a whole, including Trinity-origin fish.

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Apportioning the 2.2% Within the Klamath Basin: An AI-Derived Allocation Model

What this section is and is not: This subsection presents allocation and consumption estimates derived using AI from publicly available data. It takes the peer-reviewed 2.2% ± 2.3% figure from Hanson et al. 2021 — which lumps all Klamath Basin sub-stocks together — and (a) splits it across Trinity River, lower Klamath tributaries, and mainstem Klamath, (b) attributes the consumption primarily to L pod based on documented pod-range patterns, and (c) translates the dietary percentages into estimated fish-per-whale-per-year using standard SRKW feeding-rate literature.

None of these specific numbers come from a peer-reviewed study. No published paper has separated Klamath Basin sub-stocks in SRKW diet, attributed the K+L combined dietary figure specifically to L pod, or converted dietary percentages into absolute fish counts by stock. The numbers below should be cited as AI-derived estimates, not as published science. They are presented because the underlying questions deserve a transparent answer, and a transparent estimate is more honest than implying a precision the peer-reviewed science does not yet provide.

Step 1 — Splitting the 2.2% Across Klamath Sub-Regions

Three independent salmon production sources feed the Klamath Basin’s total Chinook output:

Trinity River side (enters Klamath at river mile 43, downstream of most of the disease zone):

• Trinity River Hatchery: ~2.9 million fall Chinook smolts + ~900,000 yearlings annually ≈ 3.8 million fall Chinook, plus ~300,000 coho and ~448,000 steelhead (Source: CDFW; Trinity River Restoration Program)
• Substantial natural production from the Trinity mainstem and South Fork
• Trinity smolts bypass essentially all of the C. shasta parasite zone before entering the ocean

Mainstem Klamath (above the lower-tributary confluences — the only reach where Klamath Project operations could plausibly affect smolt production):

• Fall Creek Hatchery (post-removal replacement for Iron Gate): production goal of 3.25 million fall Chinook + 75,000 coho annually; first-year actual release ~2.1 million smolts + ~270,000 yearlings as the new $35 million facility ramps up
• Pre-removal Iron Gate Hatchery historically produced ~6 million Chinook annually
• Smolts must traverse the entire disease zone before reaching the ocean

Lower Klamath tributaries (Scott, Shasta, Salmon Rivers):

• No hatchery production — entirely natural
• 2025 combined adult escapement: 9,192 fish (up from 7,317 in 2024)
• Smolts enter the mainstem below most of the disease zone

Step 2 — Adjusting for the Reality of In-River Survival

This adjustment is built on peer-reviewed science. The USGS Foott et al. radio-telemetry study found that hatchery Chinook smolts released at Iron Gate Hatchery had a cumulative survival rate of only about 7 percent by the time they reached the ocean. Roughly 93 percent died in the river — a survival rate consistent with what salmon experience in long river systems across the Pacific Northwest.

The science clearly shows that survival decreases systematically with distance from the ocean.

What this means for the allocation: smolts originating higher in the system have systematically lower ocean-entry survival than smolts originating lower in the basin. Translating to rough survival rates:

• Trinity-origin smolts: approximately 25–35% survival to ocean entry
• Mainstem Klamath–origin smolts: approximately 7–15%
• Scott/Shasta/Salmon-origin smolts: approximately 15–25%

Step 3 — The Sub-Basin Allocation

Combining production and survival yields the following AI-derived breakdown of the verified 2.2% basin-wide figure:

Step 4 — Why L Pod, Not All Three Pods

The peer-reviewed Hanson et al. 2021 study reports the 2.2% figure for K and L pods combined because, during sample collection, K and L pods were typically swimming together — 40 of 54 outer-coast samples (74 percent) were taken when both pods were present. The paper does not separate the contribution of each pod individually.

But independent range data from Brad Hanson’s own satellite-tagging studies (Hanson et al. 2013, 2018, both peer-reviewed and cited in the 2021 paper) and from the Center for Whale Research’s long-term observational record point clearly to L pod, not K pod, as the primary consumer of Klamath-origin Chinook. The evidence:

• J Pod (27 whales): Range confined to coastal waters off Washington and British Columbia. Klamath stocks not detected in any J pod prey samples. The Delta Council’s 2024 SRKW chapter summarizes NMFS’s position: “J pod individuals rarely, if ever, travel beyond the coastal waters off Washington and British Columbia.”
• K Pod (15 whales): Documented as ranging “intermediate between L and J pods.” Satellite tracking of one K pod whale (K-25) documented three southerly trips, all turning around at Point Reyes, California — about 150 miles south of the Klamath River mouth. K pod’s range overlaps only marginally with the ocean waters where adult Klamath Chinook concentrate.
• L Pod (34 whales): Documented by the Center for Whale Research as “most coastal in distribution” and the pod that “travels the farthest” — regularly satellite-tracked into central California waters. L pod’s documented range substantially overlaps with the ocean distribution of adult Klamath Chinook.

The ocean distribution of adult Klamath Chinook is well-documented. Most ocean recoveries concentrate in the Eureka-Crescent City port area (the Pacific Fishery Management Council’s Klamath Management Zone, latitude 40.77° to 42.67° N) and the southern Oregon coast (peer-reviewed sources: Weitkamp 2010; Satterthwaite et al. 2014; CDFW annual Coded Wire Tag Recovery Reports).

Putting it together: the Klamath dietary contribution most likely concentrates in L pod (34 whales — about 45% of the SRKW population), with K pod contribution substantially smaller and J pod contribution effectively zero. The 2.2% K+L pooled figure understates how concentrated the Klamath consumption is in L pod and overstates how many whales are affected.

Step 5 — Converting Percentages to Actual Fish

The standard feeding-rate figure for SRKWs, used by NOAA and the Center for Whale Research, is that an adult Southern Resident Killer Whale eats about 2.5% to 5% of its body weight per day. For a mixed-age pod averaging 6,000–8,000 pounds, that works out to roughly 200–300 pounds of food per whale per day.

Adult ocean-phase Chinook eaten by SRKWs average about 15–25 pounds each (the peer-reviewed Hanson et al. 2021 study documented most prey as age-4 fish, with age-3 and age-5 making up most of the rest). Using mid-range values — 250 pounds of prey per whale per day, divided by 20 pounds per Chinook — gives roughly 12–13 Chinook-equivalent meals per whale per day.

Chinook is not 100% of the diet year-round. The peer-reviewed Hanson et al. 2021 and Ford et al. 2016 studies show Chinook makes up about 50% of diet in fall/early winter, rising to nearly 100% in spring, with a weighted annual average of about 70–75%. Applying that:

An L pod whale needs approximately 3,000–4,000 actual Chinook salmon per year to sustain itself.

For the entire 34-whale L pod, that comes to approximately 100,000–140,000 Chinook per year, with a central estimate near 119,000 Chinook per year.

Step 6 — What 2.2% Actually Means in Fish

Applying the AI-derived sub-basin allocation to L pod’s annual Chinook requirement, and accounting for the fact that the 2.2% applies only to mid-winter/early-spring outer-coast foraging (not year-round, not all locations), produces these AI-derived estimates based on the peer-reviewed Hanson et al. 2021 dietary percentages:

For comparison: an L pod whale needs approximately 3,000–4,000 Chinook per year.

Step 7 — Stress-Testing the Estimate: What If L Pod Ate Only Klamath Chinook During the Transit?

A skeptic might reasonably ask: “L pod ranges right past the Klamath River mouth — couldn’t they be eating far more Klamath fish than the peer-reviewed 2.2% figure suggests?”

This sub-section answers that question with a deliberately extreme upper-bound calculation. It asks: What is the absolute maximum number of Klamath Chinook L pod could possibly consume in a year, if we assume the most generous conditions possible? Any actual number must fall below this ceiling.

The setup:

• The Pacific Fishery Management Council’s Klamath Management Zone spans latitude 40.77° N to 42.67° N — roughly Cape Mendocino to Humbug Mountain, about 150 statute miles of coastline.
• Assume L pod transits this zone twice per year — southbound and northbound — at about 9 days each direction. That’s 18 total foraging days inside the Klamath Management Zone per year.
• Assume that during every one of those 18 days, L pod eats nothing but Klamath Basin Chinook — an absolute upper bound, biologically impossible to exceed because L pod cannot eat Klamath fish when not in Klamath waters.

The upper-bound calculation:

L pod’s daily Chinook consumption during peak Chinook season is approximately 12.5 Chinook per whale per day (the high-Chinook-fraction daily rate from Step 5, applied to mid-winter/early spring when Chinook makes up nearly 100% of diet per the peer-reviewed Hanson et al. 2021 findings).

Applying the sub-basin production split:

At maximum foraging exposure, the Klamath-only diet is proportional to total basin Chinook output. Using the relative production shares of each sub-basin:

What the upper bound means:

Even under the absolute maximum possible assumption — L pod feeds exclusively on Klamath Basin Chinook during their entire 18-day transit of the Klamath Management Zone — the mainstem Klamath contribution caps out at approximately 52 fish per L pod whale per year, against an annual need of 3,000–4,000 Chinook per whale.

That is the biological ceiling. The actual figure cannot exceed it. And in reality the figure is much lower because L pod does not eat only Klamath Chinook in the Klamath Management Zone — the peer-reviewed Hanson et al. 2021 dietary data show Klamath stocks make up only 2.2% (± 2.3%) of K/L pod outer-coast mid-winter Chinook diet, not 100%, with the remainder coming from the Columbia, Sacramento Central Valley, Rogue, and other systems whose fish are also present in the same waters.

So the realistic range for the mainstem-Klamath contribution to an L pod whale’s annual diet is bounded by:

• Lower bound (peer-reviewed dietary percentages applied): ~4–6 fish per L pod whale per year (Step 6 estimate)
• Upper bound (Klamath-only diet during entire Klamath Management Zone transit): ~52 fish per L pod whale per year (this stress test)

Even at the upper bound, the mainstem Klamath contributes less than 2 percent of an L pod whale’s annual Chinook needs. At the realistic peer-reviewed-based estimate, the figure is roughly one-tenth of one percent of L pod’s annual Chinook nutrition.

Either way, the conclusion is the same: the mainstem Klamath — the only reach where Klamath Reclamation Project operations could plausibly affect smolt production — is not where Southern Resident Killer Whale recovery happens, and ordinary year-to-year variation in Project water deliveries cannot move the SRKW prey-base needle. To meaningfully affect L pod’s nutrition, you would need to change Chinook production in the Columbia, Sacramento, Puget Sound, or Fraser systems.

The 18-day transit assumption is itself an AI-derived estimate. The actual residency time of L pod within the Klamath Management Zone is not precisely documented in the peer-reviewed literature. Brad Hanson’s satellite tagging studies (Hanson et al. 2013, 2018, peer-reviewed) document L pod movements but do not break out specific time-in-zone for the Klamath Management Zone. The 9-days-each-direction figure is a reasonable estimate for a foraging pod transiting roughly 150 miles of coastline at typical resident-killer-whale travel speeds. Even if the actual residency were as long as 30 days, the upper-bound mainstem-Klamath number rises to only about 86 fish per L pod whale per year — still less than 3 percent of annual need.

What This All Means

For every Chinook salmon an L pod whale eats from the mainstem Klamath in a year — from the only reach where Klamath Reclamation Project operations could even theoretically influence smolt production — that same whale eats approximately 600 to 800 Chinook from somewhere else: mostly the Columbia/Snake system, the California Central Valley, Puget Sound, and the Fraser River.

Across the entire 76-whale SRKW population:

• J Pod (27 whales): zero Klamath contribution
• K Pod (15 whales): substantially smaller Klamath contribution than L pod; plausibly near-zero for the mainstem Klamath specifically
• L Pod (34 whales): approximately 4–6 mainstem-Klamath Chinook per whale per year

This is not a finding that the Klamath River is unimportant for ecosystem health, salmon recovery, or Tribal cultural and subsistence purposes. It is a finding that ordinary year-to-year variation in Klamath Reclamation Project deliveries cannot plausibly move the SRKW prey-base needle. To meaningfully affect L pod’s nutrition, you would need to change Chinook production in the Columbia, Sacramento, Puget Sound, or Fraser systems — not the upper Klamath.

AI-derived estimates above used: peer-reviewed dietary percentages from Hanson et al. 2021 and Ford et al. 2016; standard SRKW feeding-rate parameters (2.5–5% body weight daily; mixed-pod 6,000–8,000 lb average body weight; 15–25 lb average Chinook prey size; 70–75% annual average Chinook dietary fraction) drawn from published SRKW recovery literature; and public CDFW, USGS, NOAA, Trinity River Restoration Program, and Pacific Fishery Management Council data. Not peer-reviewed. Provided for transparency, not as published science.

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A Historical Test of the Premise: 1931 and the Strongest Chinook Run in Modern Records

The conventional regulatory framework treats higher Klamath River flows as essentially synonymous with stronger Chinook returns. The historical record does not support that premise.

The USGS Klamath River gage at Fall Creek (gage 11512500), about 50 river miles below Keno, began recording flows in October 1923. The California State Water Resources Control Board, in its December 2018 Draft EIR for the Lower Klamath Project license surrender, documents this directly:

“Mean daily flows fell below 100 cfs at USGS Gage No. 11512500 on 50 occasions between water years 1931 and 1937.”

In 1931 specifically, flows at Fall Creek dropped as low as about 87 cfs — among the lowest mainstem Klamath River flows ever measured at that location. The Dust Bowl drought was at its peak.

And yet, according to the peer-reviewed work of Leidy and Leidy (1984), cited in California Department of Fish and Wildlife historical records, annual Chinook escapement to the Klamath Basin averaged 43,752 fish from 1930 through 1937 — more than four times the escapement levels typical of the 1970s, and among the strongest fall Chinook periods in the entire modern measured record.

That period coincided with:

• Documented severe drought conditions
• Mainstem flows below 100 cfs at Fall Creek on 50 separate days
• Copco No. 1 (1918) and Copco No. 2 (1925) already in place, blocking upstream passage
• The Klamath Reclamation Project already operational and diverting water for irrigated agriculture

If low mainstem flows in the upper river were the primary limiting factor for Chinook recovery — the implicit premise of the modern regulatory framework — the 1930s should have produced one of the weakest Chinook runs on record. Instead, it produced one of the strongest.

This is not an argument that salmon don’t need water. It is an empirical demonstration that the Klamath Chinook population is far more resilient to upper-basin low-flow conditions than the modern regulatory framework assumes, and that the dominant drivers of population success and failure lie elsewhere: ocean conditions, fishery management, lower-river habitat quality, disease, and access to historic tributary habitat. The mainstem stayed slightly wet in 1931, and the salmon ran.

Sources: California State Water Resources Control Board, Draft EIR for Lower Klamath Project License Surrender, December 2018, Volume I, Section 3.6 Surface Water Hydrology; Leidy and Leidy 1984 (peer-reviewed); California Department of Fish and Wildlife historical escapement records, citing Snyder 1931.

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Distance and Disease: Why Klamath Smolt Survival Is Already Low

There is a second, biological reason that any specific Klamath water-management decision has a small effect on SRKW prey availability: most juvenile salmon produced anywhere in the Klamath system do not survive the long migration to the ocean — and the reasons have nothing to do with upper-basin water deliveries.

Smolt mortality accumulates with each river kilometer due to predation, temperature stress, energy depletion, and disease exposure. The Klamath River contains a documented “infectious zone” between river miles 141 and 190 (Iron Gate to Seiad Valley), where the parasite Ceratonova shasta causes major losses among outmigrating salmonids. This is established in peer-reviewed work by Bartholomew et al. 2015 and Stocking et al. 2006.

The peer-reviewed numbers are striking. A USGS-led radio-telemetry study of hatchery subyearling fall-run Chinook released at Iron Gate Hatchery found that only about 7 percent survived to reach the estuary. Roughly 93 percent died in the river before reaching the ocean. Survival per 100 km of migration decreased systematically with distance from the hatchery.

This same peer-reviewed survival science raises a fair question about how Klamath salmon recovery dollars are being spent. The replacement facility for Iron Gate Hatchery — the $35 million Fall Creek Hatchery — is sited at approximately the same distance from the ocean as Iron Gate was, with a production goal of 3.25 million fall Chinook annually. By the peer-reviewed survival math, a substantial fraction of those smolts will not reach the ocean. The same regulatory framework that uses peer-reviewed smolt-mortality science to justify restrictions on Klamath Project water deliveries chose to invest in a hatchery at the location where that science predicts the worst survival outcomes. Whether the post-dam-removal river will improve those numbers is an open question that several years of monitoring will resolve.

The implications for the upper-basin water debate are direct:

• Fish that originate or rear higher in the system must traverse the entire disease zone — and every additional mile of mainstem river — to reach the ocean.
• Fish from lower-river tributaries (Trinity, Salmon River) enter the mainstem below most of the disease zone, which is one reason Trinity-origin Chinook are more represented in offshore Chinook prey than mainstem Klamath fish.
• These mortality factors are properties of the river system itself — disease, temperature, predators. They are independent of Klamath Project operations.

For SRKW prey availability, the marginal effect of any specific increment of upper-basin water management — more flow, less flow, full deliveries, restricted deliveries — on the number of Klamath-origin fish actually reaching SRKW foraging zones is small, because the in-river survival fraction is itself small.

Peer-reviewed sources: Foott et al. (USGS); USGS Open-File Report 2019-1099 (Stream Salmonid Simulator); USGS Open-File Report 2022-1106; Bartholomew et al. 2015 (PLoS ONE); Stocking et al. 2006.

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What the Best Recent Peer-Reviewed Economics Says: Salish Sea Vessel Noise, Not Klamath Water, Is Driving SRKW Decline

The single most rigorous recent empirical study of what is actually driving SRKW decline is the work of University of Calgary economist M. Scott Taylor and co-author Fruzsina Mayer, published as NBER Working Paper No. 31390 (June 2023) and synthesized for general audiences in the September 2025 PERC report Saving Killer Whales Without Sinking Trade.

Taylor is past president of the Canadian Economics Association, director of the Kuehne Center for Sustainable Trade and Logistics at the University of Zurich, and a research associate at the National Bureau of Economic Research. His work has appeared in the American Economic Review, Quarterly Journal of Economics, and Review of Economic Studies.

Using the full Center for Whale Research SRKW census data from 1977 through 2019, and matching it to commercial vessel-traffic data in the Salish Sea, Taylor and Mayer ran a natural-experiment econometric analysis. Their peer-reviewed findings:

1. Noise pollution from commercial shipping in the Salish Sea is the dominant driver of SRKW decline. Ambient ocean noise has risen by three to four decibels per decade since the 1950s — from about 52 dB in 1950 to over 90 dB by 2007.
2. A 40-year-old SRKW is more than 30% more likely to die in a noisy year than in a quiet year, controlling for age, sex, and prey availability.
3. Female SRKWs are more than 25% less likely to produce a successful birth after a noisy year, accounting for the 15–18 month gestation period.
4. More salmon alone cannot solve the problem. Their model finds that offsetting the negative impact of Salish Sea noise on SRKW would require a permanent three-standard-deviation increase in salmon abundance — a level not recorded in the entire 20th century. In their own words: “restoring salmon stocks alone is unlikely to undo the impact of noise disturbance on killer whales.”
5. If Salish Sea noise had stayed at pre-2000 levels, SRKW would be about 30% larger today than it actually is — essentially reversing the post-2000 decline.

A natural comparison group strengthens the finding. The closely related Northern Resident Killer Whales inhabit the same general Pacific Northwest waters, but their range contains no large international ports. Over the same 1970s-to-present period during which SRKW have stagnated or declined, the Northern Residents grew from about 100 individuals to more than 330 — nearly continuous growth at roughly 2% per year. The two populations share genetics, ecology, prey species, fisheries pressure, climate, and contaminant exposure. What they do not share is exposure to heavy commercial vessel noise.

The PERC report proposes a market-based noise-permit system to address the problem at its source. Whatever one thinks of that specific policy idea, the underlying empirical finding stands on its own peer-reviewed merits: the dominant SRKW recovery lever is reducing Salish Sea vessel noise. It is not increasing salmon abundance, and it is certainly not constraining water deliveries 250+ river miles inland in a basin that already contributes a statistically-indistinguishable-from-zero share of SRKW diet.

This finding is also consistent with the 2026 NOAA perspective paper by Ford, Ward, Kardos, Parsons, Emmons, and Hanson (peer-reviewed, Ecology and Evolution), which identifies vessel and noise disturbance as one of the five major SRKW risk factors alongside prey availability, inbreeding, contaminants, and interactions with other killer whale populations.

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What the Project Actually Does to River Flows

The Klamath Reclamation Project lies in the Upper Klamath Basin, more than 250 river miles upstream from the river’s mouth. It sits above Keno Dam and the former Iron Gate Dam site — reaches that were inconsistently accessible to anadromous salmon for thousands of years before any human-made dam, due to natural geological barriers.

Here is what the Project actually does to flows in the mainstem Klamath, by water year type:

• Wet years: The Project increases water available to the lower Klamath River. By storing surface inflow into Upper Klamath Lake during high-water periods and releasing it through Link River Dam during periods that would otherwise be lower-flow, the Project effectively shifts water from high-flow seasons (when salmon don’t need it) to lower-flow periods (when they do). Net effect on downstream availability: positive.
• Average years: The Project has approximately neutral net effect on downstream volumes. Diversions to irrigated agriculture are largely offset by return flows entering the river through the Lost River Diversion Channel, the Klamath Straits Drain, and other return-flow features.
• Dry years: Project diversions are constrained by Biological Opinion requirements, drought-tier delivery rules, Upper Klamath Lake elevation requirements, and Keno Dam compliance flows. The mainstem stays wet. Diversions above what natural conditions would have produced are minimal.

Tributary inputs from the Scott, Shasta, Salmon, and Trinity Rivers downstream of the Project area are large compared with anything the Project does to upper-basin hydrology. Seasonal Klamath hydrology is dominated by snowpack and natural climate — not by upper-basin agricultural diversion patterns.

The premise that ordinary year-to-year variation in Klamath Project deliveries materially affects flow conditions in the reaches where anadromous salmon actually live is not well-supported by the hydrology. It is even less well-supported by the historical record above.

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SONCC Coho and the Mainstem Klamath in Summer

Threatened SONCC coho salmon — listed in 1997 — were a central species in earlier decades of Klamath water litigation. The current science, synthesized in the peer-reviewed Lestelle (2022) review, shows that juvenile SONCC coho do not rear in the warm mainstem Klamath River during summer. They shift to cold-water refuges in tributaries (Scott, Shasta, Salmon Rivers), spring complexes, and off-channel habitats like beaver ponds and side channels.

Mainstem temperatures in the lower Klamath routinely exceeded 22°C in summer when the four lower-river dams were operating — close to or beyond juvenile coho thermal tolerance. That pattern was driven primarily by the dam reservoirs acting as “heat batteries,” not by upper-basin agricultural water use. Post–dam-removal monitoring confirms that mainstem temperatures are now normalizing.

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What’s Happened Since Dam Removal

If the long-standing theory had been correct — that upper-basin water management was a meaningful driver of salmon decline and orca prey loss — then removing the four lower dams while Project operations continued would test it. Here is what one year of post-removal data shows:

• 51,277 adult fall-run Chinook returned to the basin in 2025 — at 205% of the preseason forecast of 19,417 adults.
• 39,860 adults spawned naturally, essentially on par with the 40,700-adult floor escapement goal.
• Hatchery returns of 7,623 adults, up from 4,489 in 2024.
• Jack (two-year-old) returns of 18,574, up from 7,085 in 2024 — a strong leading indicator for 2026.
• Upper Basin tributary escapement (Salmon, Scott, Shasta Rivers): 9,192 adults in 2025, up from 7,317 in 2024.
• Chinook documented spawning more than 360 river miles from the ocean — in the Wood, Williamson, and Sprague Rivers in Oregon — for the first time in over a century.
• Sonar counts at the former Iron Gate site recorded more than 10,000 large Chinook in fall 2025, a 30% increase over fall 2024.
• Microcystin algal blooms collapsed below the former Iron Gate site: 58% of samples previously exceeded the public-health limit; 100% are now below the limit, with 82% non-detectable (CDFW and Karuk Tribe water-quality monitoring).
• Water temperatures are normalizing — faster spring warm-up (aiding juvenile outmigration) and faster fall cooling (aiding adult spawning).

The 2025 returns are particularly remarkable in light of what FERC predicted and what actually happened. FERC’s 2022 Final EIS predicted “short-term, significant, unavoidable, adverse effect[s] on all life stages of anadromous fish that are present in the Lower Klamath River during the drawdown year.” Field monitoring confirmed those short-term losses in the 2024 brood. The fact that adult returns one year later still ran at 205% of forecast — with the Klamath Project continuing to deliver water throughout — is empirical confirmation that the basin’s salmon production is more resilient and more responsive to dam removal and habitat restoration than to upper-basin water deliveries.

Sources: California Department of Fish and Wildlife — “Salmon Everywhere” One Year After Klamath Dam Removal (Nov. 2025); Fishing the North Coast — 2025 Klamath fall Chinook return reporting (Feb. 2026); NOAA Fisheries Klamath dam removal feature.

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Comparing the Claims to the Facts

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What the 2024 NMFS Biological Opinion Says — and What It Does Not

On October 28, 2024, the National Marine Fisheries Service (NMFS) issued its current Biological Opinion governing Klamath Project operations from October 1, 2024 through September 30, 2029. Its conclusion:

“In this biological opinion, NMFS concludes that the proposed action is not likely to jeopardize the continued existence of the Southern Oregon/Northern California Coast (SONCC) coho salmon Evolutionarily Significant Unit (ESU) or the Southern Resident Killer Whale Distinct Population Segment (DPS) (SRKW), or destroy or adversely modify designated critical habitat for the SONCC coho salmon ESU or SRKW.”

That is a no-jeopardy finding for both species — issued by the federal agency charged with administering the ESA, after consultation, technical review, and inclusion of the most current science.

NMFS did find the proposed action “likely to adversely affect” both SRKW and SONCC coho — but concluded those adverse effects do not rise to the level of jeopardy or adverse modification of critical habitat. That distinction is consistent with the peer-reviewed dietary science: a small adverse effect on the basin-wide 2.2% Klamath dietary share (most of which is Trinity-origin and outside the Project’s reach) does not approach the threshold at which the SRKW population would be jeopardized.

It is important to be precise about what NMFS evaluated. Section 7 consultations evaluate a specific proposed action submitted by the action agency — in this case, the Bureau of Reclamation’s June 2024 Biological Assessment. That proposed action already includes substantial curtailments to Klamath Project deliveries: Keno Dam compliance flows, drought-tier rules, Upper Klamath Lake elevation requirements, and other operational constraints that meaningfully reduce water available to KID and other Project water users compared to their state water rights.

In other words, the 2024 BiOp concluded “no jeopardy” for an operating regime that already restricts deliveries to farmers. NMFS did not evaluate, and could not evaluate, what would happen under full deliveries consistent with KID’s water rights — because no such proposed action has been submitted by Reclamation for federal consultation in the modern record.

Source: NMFS, 2024 Klamath Project Biological Opinion, transmittal letter dated October 28, 2024.

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The Question Federal Agencies Have Never Been Asked

The Klamath River is fundamentally different today than it was when the foundational decisions restricting deliveries to KID were made.

• Four mainstem hydroelectric dams — Copco No. 2, J.C. Boyle, Copco No. 1, and Iron Gate — were removed between summer 2023 and October 2024.
• Hundreds of miles of historic salmon habitat upstream of Iron Gate have been reopened. CDFW documented Chinook reaching Oregon tributaries (Wood, Williamson, Sprague Rivers) for the first time in over a century during fall 2024 and 2025.
• Mainstem water temperatures in the lower river are normalizing.
• Toxic microcystin algal bloom levels below the former Iron Gate site, which previously exceeded public-health limits in 58% of samples, are now below limits in 100% of samples — non-detectable in 82% (CDFW and Karuk Tribe water-quality monitoring).
• Salmon are reaching tributaries in the Upper Basin for the first time in over a century.

Every Klamath Project Biological Opinion in the modern record — 2002, 2008, 2010, 2013, 2019, and the proposed actions feeding into them — was developed under pre–dam-removal river conditions. The operating rules currently constraining deliveries to Klamath farmers were calibrated against a Klamath River that no longer exists.

The question that has never been formally evaluated by NMFS, USFWS, or any federal agency is this: Under post–dam-removal Klamath River conditions, what level of deliveries to the Klamath Project is consistent with the survival and recovery of SONCC coho and SRKWs?

KID is asking that the current science be applied to a current proposed action under current river conditions. That has not happened.

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Conclusion

The narrative that Upper Klamath Basin farmers are jeopardizing the survival of endangered orcas is not supported by:

• The internal logic of the federal record itself. FERC’s 2022 Final EIS, which approved dam removal, accepted on the record short-term salmon losses far greater than anything attributable to upper-basin water management and concluded those losses produced only a “less than significant” effect on SRKW. If that finding is correct, ordinary Klamath Project operational variation cannot rise to the level of an SRKW jeopardy issue. The federal record cannot have it both ways.
• The historical record. The 1931–1937 period combined documented severe drought, mainstem flows below 100 cfs on 50 separate days at Fall Creek, partial dam blockade of upstream passage, and ongoing Klamath Project diversions — and produced annual Chinook escapement averaging 43,752 fish, among the strongest run-strength periods in the modern measured record. The premise that higher upper-basin flows are necessary for strong Chinook returns is not supported by what actually happened when flows were low.
• The 2024 NMFS Biological Opinion, which found no jeopardy for the constrained operating regime currently in place.
• The peer-reviewed dietary science (Hanson et al. 2021), which finds the entire Klamath Basin contributes 2.2% ± 2.3% of K/L pod outer-coast diet — statistically indistinguishable from zero — and which does not detect Klamath stocks in J Pod or summer Salish Sea diet.
• A transparent AI-derived allocation of that basin-wide 2.2% across Trinity (~1.3%), lower tributaries (~0.4%), and mainstem Klamath (~0.5%) — meaning the portion of SRKW diet attributable to the only reach where Klamath Project operations could have any influence is approximately half of one percent of K/L pod mid-winter outer-coast Chinook prey, translating to roughly 4–6 fish per L pod whale per year against a need of 3,000–4,000 Chinook per whale per year, and effectively zero everywhere else in the population.
• The peer-reviewed economics (Taylor & Mayer, NBER 2023; PERC 2025), which identifies Salish Sea commercial-vessel noise pollution — not salmon abundance, and certainly not Klamath water management — as the dominant driver of SRKW decline, with the natural comparison to Northern Resident Killer Whales (which inhabit quiet waters and have grown from ~100 to ~330 individuals over the same period) reinforcing the conclusion.
• The basic geography of the Project — 250+ river miles upstream of orca foraging zones.
• The hydrology of the Project’s actual operations — neutral to positive net effect on downstream flows in wet and average years, minimal additional impact in dry years, with the mainstem remaining wet at all times.
• The biology of Klamath smolt outmigration — cumulative in-river mortality has historically reduced ocean-entry survival to roughly 7%, regardless of upper-basin flow management.
• The post–dam-removal data — 51,277 adult Chinook returning at 205% of forecast while the Project operates.

What the science does support is a long-overdue, current-conditions evaluation of what level of deliveries to Klamath Project water users is consistent with species recovery under the post–dam-removal Klamath River. That evaluation has not been performed. The operating constraints in place today reflect a river that no longer exists.

Klamath Project water users have been active partners in habitat restoration, wetland creation, water-quality improvements, drought response, and tribal coordination for decades. They are part of the recovery story — not the obstacle to it. If society is serious about Southern Resident Killer Whale recovery, the conversation needs to move from 250-mile-distant agricultural deliveries to the actual peer-reviewed drivers: Salish Sea vessel noise, Fraser River prey base, Columbia/Snake fisheries management, and the genetic and demographic stressors specific to a population of 76 animals.

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Key Documents and Sources

Federal record:

• FERC Final EIS for Lower Klamath Project Decommissioning, August 2022 (see Table ES-2 for the ~2.3% SRKW finding)
• FERC Final EIS Appendices
• NMFS 2024 Klamath Project Biological Opinion
• California State Water Resources Control Board — Draft EIR for Lower Klamath Project License Surrender, Section 3.6 Surface Water Hydrology (Dec. 2018) — documents 50 days below 100 cfs at Fall Creek 1931–1937

Historical Chinook abundance:

• Snyder 1931 (original survey of California coastal Chinook)
• Leidy and Leidy 1984 — Klamath Basin Chinook escapement 1930–1976 (peer-reviewed)
• CDFG 1965, 2006 — historical escapement compilations

Peer-reviewed SRKW diet science:

• Hanson et al. 2021 — Seasonal diet of Southern Resident killer whales (PLoS ONE)
• Ford et al. 2016 — Summer Salish Sea diet of SRKW from fecal DNA (PLoS ONE)
• Ford et al. 2026 — Perspective on SRKW Future (Ecology and Evolution)

Peer-reviewed SRKW driver economics:

• Taylor & Mayer 2023 — International Trade, Noise Pollution, and Killer Whales, NBER Working Paper No. 31390
• PERC 2025 — Saving Killer Whales Without Sinking Trade (M. Scott Taylor)

SONCC coho life history:

• Lestelle 2022 — SONCC Coho Life History Review (peer-reviewed)

Klamath smolt outmigration and disease:

• Foott et al. (USGS) — Pilot study on Chinook smolt outmigration in the lower Klamath
• USGS Open-File Report 2019-1099 — Stream Salmonid Simulator (S3) Klamath
• USGS Open-File Report 2022-1106 — Post–dam-removal Chinook simulation
• Bartholomew et al. 2015 — Disease-induced juvenile mortality (PLoS ONE, peer-reviewed)

Post–dam-removal monitoring:

• California Department of Fish and Wildlife — “Salmon Everywhere” One Year After Klamath Dam Removal (Nov. 2025)
• Fishing the North Coast — Klamath Fall Chinook Return Tops Expectations in 2025 (Feb. 2026)
• NOAA Fisheries — Final Step in Klamath River Dam Removal

SRKW population:

• Center for Whale Research — Southern Resident Orca Population

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Reviewed and revised May 2026 by the Klamath Irrigation District Science Review Team. This version incorporates plain-language rewrites for general public readability while explicitly marking which claims are supported by peer-reviewed science and which are AI-derived estimates based on transparent assumptions. Prior versions published August 2025 and earlier May 2026.

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