SOS Blog: Lessons from the 2015 Columbia-Snake Salmon Kill
From the desk of Pat Ford
August 1, 2016
In late spring and summer of 2015, an estimated 250,000 adult salmon died in the main-stem Columbia and Snake Rivers while trying to reach their home waters to spawn their next generation. The main cause was 70 days of sustained hot water in both rivers. Water temperatures at Bonneville Dam on the Columbia, and Ice Harbor Dam on the lower Snake, hit 68 degrees F on June 24, rose quickly to 72-73 degrees for two weeks in early July, and did not fall below 68 degrees again at either dam until early September. (68F, or 20C, is the reference temperature – an aim, not a requirement – established by NOAA Fisheries to protect Columbia-Snake salmon and steelhead from the adverse effects of hot water.) Two other factors also contributed to the kill: a low 2014-15 snowpack that led to low 2015 runoff, and the dam-and-reservoir system whose baseline stresses to migrating salmon in both rivers exacerbated the hot water effects.
This major salmon kill has sparked wide concern among people who care about the salmon and health of the Columbia and Snake. Spring and summer river temperatures in both rivers have been rising for several decades now, and Northwest climate and salmon scientists expect the trend to continue as human-caused climate change pushes global air temperatures upward. In the wake of 2015, many Northwest people are asking with urgency, what can we do to help salmon successfully migrate climate change? What’s in our toolbox now, and what new tools can we add?
To tackle these questions in some detail, I have been reading and talking to Northwest climate and salmon scientists, be they researchers, fish managers, or both. The full result will be released in a few months, but the Hot Water Report 2016 presents an opportunity to preview some of the findings, and solicit reaction. I begin with the first question I am asking scientists: what lessons should people who care about salmon, and people making salmon, energy and water policies, take from 2015’s salmon kill? Here are the main answers so far.
1. 2015 was a preview, a harbinger, of a new summer normal that climate change is establishing in the Columbia and Snake Rivers. Most scientists I talked with believe the extreme conditions in 2015 were mainly due to natural climate variability, but also worsened by human-caused climate change and other human alterations to both rivers. All believe these conditions will repeat and expand in extent and duration, until they constitute “a new normal” a few decades from now. Two to six decades is the range I’ve heard; scientists are more confident of the trend than of its pace. One of many effects on salmon is that the extent and severity of large kills like 2015’s will increase (ISAB and ISRP, 2016).
2. Summer migrating species – sockeye salmon, summer Chinook salmon, and summer-migrating steelhead – are most at risk. All or major parts of the adult migration of these species, from the ocean and through the Columbia and Snake Rivers to their spawning areas, occurs in summer. [footnote: Spring Chinook, fall Chinook, late-run steelhead, and coho are not exempt from this new summer normal, since parts of their migrations also occur in summer. And, though attention in 2015 was on adult salmon returning from the ocean, the same hot water also beset summer-migrating juvenile salmon on their way to the ocean. We must wait for adult returns of this age class in 2017 and 2018 for data specifically on them, but it’s certain that intensified hot water will have harmful effects on both juvenile and adult fish.] Water is already lowest then, water temperatures hottest, and the dam-and-reservoir environments that dominate both rivers most stressful due to complex combined effects with temperatures and flows. Now climate changes are making the low waters lower, the hot temperatures hotter, and dam and development effects more stressful for these species, many of which are already endangered or threatened with extinction. (Chapman 2011)
Sockeye seem to be at greatest risk. In 2015, over 200,000 upper Columbia sockeye died before reaching their Okanogan and Yakima Valley spawning lakes, and 95% of Snake River sockeye were killed by hot water before reaching Idaho (NOAA 2016). Progress that these Columbia sockeye have recently made toward renewed abundance, and endangered Snake River sockeye have made toward survival, hit a wall of hot water in 2015. In addition, the Fish Passage Center found that “survival of adult migrating summer Chinook salmon was a historical low in 2015 coincident with high water temperatures” (FPC 2016). Salmon are resilient to one-year catastrophes, but resilience will be ground down as what we now call extreme conditions become normal in summer.
3. “We knew it would come, we were surprised, we weren’t ready.” These partially inconsistent reactions express the situation for salmon managers in 2015. Water temperatures above biological standards for salmon have been routine in the Columbia and Snake main-stems, and some tributaries, since at least the 1990s, gradually increasing in scope and severity. Salmon mortalities as a result have been documented prior to 2015. Plans to abate the problems were recommended or promised (NOAA 1995; EPA 2001). Scientists warned that catastrophic episodes affecting summer migrants were likely to certain (Chapman, 2011). Yet the 2015 episode caught most managers, and more importantly management systems, by surprise. No plans were in place to guide response by federal, state and Tribal fish managers [NOAA 2016, FPC 2016].
4. The management tools available today are not sufficient. As 2015’s catastrophic conditions become normal, the dam-and-reservoir system, as currently configured, cannot be manipulated to significantly abate the harmful effects on salmon. The same is likely true of hatchery systems.
A mini-demonstration is underway in 2016. While 2016 river temperatures have not been as extreme as 2015’s, they are still warmer than past averages. Fishery and dam managers have been weighing actions to help keep summer temperatures, in the rivers and in specific fishways, below 68 degrees F. Limited supplies of cold water available from storage reservoirs, if used to help salmon migrating in early or mid-summer, are not available to help salmon migrating later in the summer. Some measures to help adult salmon pose risks to juvenile salmon also present in the rivers. Energy, navigation, and flood control probability rules that dominate the main-stems take other salmon measures off the table from the perspective of dam managers. One fish manager put the situation he and colleagues face this way: “Which way do we want to hurt fish? It’s our call.”
5. Focus on the ecological context. The 2015 salmon kill shows that hot rivers and reservoirs, a main result of climate change now and to come, cause big problems for salmon. Therefore, river temperatures are a lead indicator to track closely, seek to reduce, and seek to buffer salmon against.
But climate change’s effects on salmon and rivers can’t be measured, or responded to, by attention to one parameter only. Rising river temperatures are a lead barometer of those effects, but not a single consequence that we should try to singly fix. Climate change is affecting the entire suite of dynamic conditions in rivers and ocean that affect salmon. An ecosystem approach, which seeks to return toward or mimic the complex river conditions under which salmon evolved, must guide successful salmon recovery, whether in response to development and dams, or to climate change (Return to the River, 2006).
In some future installments, I will return to some of these lessons in more detail. -PF