Stuck between a creek and a hot place: Why our rivers are getting warmer

 When I give my ‘elevator-speech’ summary of my research—I study the effects of hot river temperatures on juvenile salmon behavior and the importance of coolwater refugia…—a common question I get is, ‘But why are river temperatures rising?’ Sometimes people are a little abashed about asking, since it seems like a simple question… but really, it’s a great question, and the answer has considerable nuance.

A recent study of 40 rivers across the U.S. found that most showed significant increases in water temperature over the past half-century.¹ A combination of factors affect stream temperatures, including air temperatures, amount of solar input, and land-use (e.g. urbanization, farming, and river management). This makes sense both intuitively and from experience—rivers in tropical climates are on average warmer than in the Arctic, and small high mountain streams are colder than large rivers near their delta (where they are both larger and less shaded, and are therefore open to a lot more solar radiation).

Air temperature is a strong predictor of water temperature, and increases in air temperatures due to global warming are causing a trend of increasing stream temperatures.^1,2 However, this is not the whole story. Urban areas create ‘heat islands’ that can increase water temperatures both through hotter ambient air temperatures, as well as heated water run-off from hot pavement. In addition, land-uses such as irrigation and dams can exacerbate the warming trend further, by storing water in slow-moving or shallower areas (such as irrigation ditches and reservoirs) where it heats up before returning to the river. For example, on the Klamath River where I do my research, the Iron Gate Dam (lowest of 6 on the river) is an old dam that releases water downriver from the top of the reservoir, water that has been sitting in the sometimes 100°F summer heat all day. As a result, summer water temperatures on the Klamath can reach ~80°F (26°C), which feels like bathwater, and is nearly lethal for coldwater-adapted fish like salmon.

There are many problems associated with rising river temperatures, and not just for salmon. Warmer water temperatures can cause increases in primary productivity and lower dissolved oxygen levels, effects that cascade up through the ecosystem, changing aquatic habitat structure and availability, invertebrate community composition, habitat suitability for many fish species, and often making the ecosystem more susceptible to invasive species. On the Klamath River, the summer hot water temperatures combined with eutrophication (excess nutrients, often from farm run-off) cause massive green-algae blooms in the reservoir by late summer, which get released downstream and turn the whole river green.

The Klamath River during an algae bloom

Halting the trend in rising water temperatures is linked to the problem of stopping increasing air temperatures (and rising atmospheric carbon dioxide), and will not be a quick fix. However, there is significant mitigation and restoration that we can do to lessen the impact of elevated water temperatures, solutions ranging from urban greening to dam removal to in-stream habitat restoration. This is where my research fits in—salmon are a coldwater fish, and on rivers like the Klamath, summer water temperatures can reach levels that are sometimes lethal. As a result, the fish seek out colder areas in the river (coolwater refugia), often created by incoming coldwater tributaries. Protecting and restoring these refugia are an important way that we can mitigate the effects of hot summer rivers temperatures on salmon.

Juvenile salmon piling into a thermal refugia on the
Klamath River (photo by Kyle Swann) 

It’s important to note that knowledge of the long-term trends in river water temperatures, as well as the data that produced the now famous graphs of rising C0₂ trends, would not be possible without long-term monitoring projects that were established years ago. These kinds of long-term programs are hard to fund and maintain, yet are essential if we want to understand how our environment is changing over time—this is an interesting problem that my lab is currently researching. Stay tuned!

1) Kauschal, S. et al. (2010). “Rising stream and river temperatures in the United States.” Frontiers in Ecology and the Environment.

2) Webb, B. et al. (2007). “Long-term changes in river temperature and the influence of climatic and hydrological factors.” Hydrological Sciences Journal.

Fish ‘n’ Chips… in Laos?

I had the best fish and chips of my life last week, and I was nowhere near England. We were traveling in Thailand and Laos for the past two weeks. In Luang Prabang, Laos, a sleepy river town along the Mekong River, still touched by the influence of French colonization (at least in cuisine and architecture), after three days of weathering the near 110F heat (and ~80% humidity), we treated ourselves to some Western food for dinner. I had a brief internal struggle over whether I should order fish and chips in Asia, but then desire took over, and I went for it. (However, I shouldn’t have worried, given the deliciousness of the Pain au Chocolat all over town). And what I realized—in between exclaiming for the 27^th time to Pete how delicious it was—is that I’ve never really liked fish and chips because of the fish (not because of the way it was cooked). Fishy-tasting haddock has nothing on the light, fresh Mekong mystery fish. Inevitably, this got me curious about Mekong fish species, and the state of the fishery there.

Delicious Laotian food, featuring brown sticky rice and chicken laap

It turns out that the Mekong has the second highest fish species richness in the world, surpassed only by the Amazon.¹ Some of its native fish species look as though they have been lifted straight from the Pleistocene—600lb giant catfish (which I admit I fantasized would leap out of the water by our boat), and a freshwater stingray that supposedly reaches 1200 pounds! However, in what is a sadly familiar story, the fish diversity is threatened, as many of these species are suffering severe population declines from a combination of overfishing, water pollution, and upstream dams. This is particularly concerning for a country where much of the rural population relies on local fish as the cheapest source of protein.¹ At the moment, the main threat to these fish is hydropower development, which under certain development projections could cut off 81% of the Lower Mekong Basin to fish migration, and turn 43% of the this section of river into a reservoir.² There are currently 16 dams in the Lower Mekong, 47 more planned for completion by 2015, and 77-88 more to be completed by 2030… an astounding rate of development.² But unlike the U.S., which is currently removing more dams than it’s building, many developing countries are still in the dam building phase. As well as being concerning, this presents an opportunity to research alternative, or at least more environmentally sound, solutions. Perhaps we should move to Laos.

Mekong River at sunset, Luang Prabang

Local fish at market

 We got to observe some interesting native fishing practices while in Laos. On our daytrip up the Mekong to a cave full of over 4000 Buddha statues, we saw people in small wooden fishing boats whacking the water with long sticks. At first, we couldn’t fathom what they were doing—the parting of the Mekong?—but then we saw them jump in the water and haul in fishing nets. Somehow, slapping the water with the poles was encouraging, or even herding, the fish into the nets. Unfortunately we didn’t have a chance to find out what kind of fish they were catching… but perhaps it’s the same kind that ended up in my belly later that night.

Fisherman on the Mekong

On the boat trip up to Pak Ou Caves

While I’m not sure what kind of fish was served up in the fish and chips that warm night in Luang Prabang—the awkwardness of the language barrier dissuaded me from asking—one way that we, as consumers, can have some sway over the commercial fishery is by being informed fish buyers. My husband and I often embarrass whomever we’re dining out with by asking the waiter where the fish came from (yes, Portlandia style, although I usually forbear from asking the fish’s name). In fact, on our trip to Thailand, we were eating out in an elegant Bangkok restaurant with family, and Pete and I began discussing where the salmon might have come from… only to be greeted by a snort of laughter from across the table. My sister-in-law and her friend had made a bet that we would ask about the salmon (while they cringed in embarrassment)… and indeed, they were right.

In an interesting example of how effective consumer pressure can be, a professor at UC Santa Cruz recently had his Marine Conservation class research which food markets in town sold environmentally sustainable fish, and then create a little pamphlet ranking them (red/yellow/green). Within a week, he got a call from one of the yellow-ranked stores asking how they could change. They were concerned about their public image. Shame, as it turns out, is an excellent motivator. (Even more so than guilt).

We have incredible power as consumers. And the more people that ask where fish comes from when they sit down to eat, the less socially weird it becomes. As “dancing guy” shows, be the one to set the trend…

1) Mekong River Commission (2010). "State of the Basin Report, 2010." MRC, Vientiane, Laos.

2) Baran, E. et al. (2012). “Fish Biodiversity Research in the Mekong Basin.” Ecological Research Monographs.

Who’s eating all the fish?

What are the major causes of salmon mortality? Unsurprisingly, this is one of the major questions in salmonid research. Of the thousands of eggs that an individual adult female salmon lays, on average only 1-2 adults return to successfully spawn. Salmon have a complex life history, spanning both freshwater and marine realms; there are many opportunities for them to die along the way, but it’s not always easy for researchers to parse out what’s killing them, and at which life stage.

This week, I helped out one of my lab-mates who’s studying one aspect of this complex question. She’s trying to figure out whether bird predation is a major cause of juvenile steelhead mortality in several small creeks just north of Santa Cruz, California. However, quantifying predation can be extremely difficult—the challenge is not just to show whether one animal is eating another, but also to quantify the predation rate (i.e. what percentage of the out-migrating juvenile salmon population is being eaten?). To do this, she and several researchers at the National Marine Fisheries Service lab in Santa Cruz came up with an ingenious method. A local biologist discovered a PIT tag (a small tag used to individually ID fish) on the nearby Año Nuevo Island, sparking the question: are birds eating young salmon in the creek and estuary and then depositing the tags (i.e. crapping them out) on the island?

The old foghorn keeper's house from the late 19th century

Año Nuevo Island is a beautiful state reserve just off the coast north of Santa Cruz, and provides important breeding and resting habitat for Northern Elephant Seals, California and Stellar’s Sea Lions, Rhinoceros Auklets, Brandt’s Cormorants, and Western gulls. At this time of year, its beaches and rocky terraces are teeming with wildlife—elephant seal pups, abandoned by their mothers and resting until they’re ready to start their own ocean journey, lie in adorable, fat, glassy-eyed piles. Huge droves of California sea lions blanket the beaches as well, barking noisily. And Western gulls add to the relentless cacophony; it’s a place that is at once peaceful and frantic, depending on your mood and ability to filter out the constant noise.

Sea lions and elephant seals blanketing the beach of the island

Wallowing baby elephant seals

We made a research trip out to the island yesterday to search for the PIT tags, heading across the ~1km stretch of ocean in a tiny dingy, banging the sides to scare off over-curious marine mammals. Our mission was to use a PIT tag detector to scan as much of the island as possible (marine mammals permitting)—the detector picks up the individual tag ID if it’s near a tag. Luckily, we didn’t need to actually find or retrieve the tags, since they are about the size of a grain of rice. Data on how many PIT tags are found and the detection likelihood, combined with data on total out-migrating salmon population size, will allow us to estimate avian predation rates on juvenile salmon in nearby creeks. In addition, the tags will tell us which particular individual fish were eaten, allowing us to quantify the characteristics of these fish to see if there is size-based mortality (i.e. were these fish disproportionately small or large compared to the average size of fish in the out-migrating population?)

Western gulls staking out their territory

Scanning for PIT tags

Estimating predation rates, as well as pinpointing potential predators, is an important step towards good management practices. So what are the potential predators that could be depositing these tags on the island? Possible culprits include avian predators—Western gulls and Brandt’s cormorants both use Año Nuevo Island for breeding—but also California sea lions, who also eat salmon. Determining which of these possible predators is actually depositing the tags on the island requires more (past and ongoing) research, including several studies analyzing the diet and movement patterns of Western gulls.

Oysters versus Wilderness: what’s the “right” choice?

Being a nature-lover at heart, most of the time when I hear about a new National Park or designated wilderness area, I’m happy. However, I wasn’t so sure about the recent wilderness designation of California’s Drakes Estero (just north of San Francisco). The problem is not that it’s protected—I’m all for preserving wilderness areas for the purposes of species’ habitat protection, biodiversity, recreation, and just to make sure there’s no development in some of our beautiful natural areas— but rather that in designating it as official wilderness, it necessitated the shut-down of a historic oyster farm (open since 1932) that provides about 40% of California’s commercial oyster supply. The root of the problem, I believe, lies in how we define and view wilderness.

On Nov. 27^th 2012, Secretary of the Interior Ken Salazar gave Drakes Bay Oyster Company 90 days to shut down operations for good, since it lies within Point Reyes National Seashore, and is therefore in violation of the National Park’s mission and regulations. Drakes Bay Oyster Company has been producing commercially-sold oysters since 1932. They pride themselves on being a sustainably-run family business, a model of sustainable local farming. They use no artificial inputs, chemicals, or feed, and are ranked as a “best choice” on the Monterey Bay Seafood Watch list. This does not mean that there are no negative environmental impacts of oyster farming in Drakes Bay—all human activities and interactions with nature come with some associated cost-benefit trade-off. The question is, what is that balance? The United States Wilderness Act of 1964 defines wilderness as “an area where the earth and its community of life are untrammelled by man, where man himself is a visitor who does not remain”—this definition leaves little room for alternative uses of official wilderness. And therefore, when Salazar made the decision to officially turn Drakes Estero into a federally designated wilderness area, the oyster farm had to close.

Clem Miller
(or Bates from Downton Abbey?)

Point Reyes National Seashore was first established in 1962 by Clem Miller, a congressman from Marin County who envisioned an area protected from residential development, but that would keep the historic ranching and oyster farming as part of the multi-use park. (This was one of the reasons that it wasn’t originally designated as a National Park.) Being a scientist, I wanted to understand the science behind these decisions, and whether the environmental benefit of closing the oyster farm outweighed the benefit of maintaining a locally sustainable farm that employed about 30 people and provided almost half of California’s oysters. (And since I’ve only recently come round to realizing that oysters are in fact utterly delicious, it is even more sobering to think that there may be a serious shortage of them in the near future).

Anne and I enjoying the fruits of the sea in Seattle 

So, what are the negative environmental impacts of oyster farming? There have been limited scientific studies done on Drakes Estero and the impact of oyster production, but there are some (as well as many studies on oysters in other systems). One potential problem is increased nutrient load in the sediment as a by-product of filtration. Oysters are filter feeders, gathering particles of phytoplankton and nutrients from the water with their cilia. The problem is that all this particulate matter and nutrients is then transferred (i.e. excreted) into sediment, creating potential anoxic (low oxygen) conditions and smothering native eelgrass beds. However, studies in Drakes Estero have shown high flushing rates with the ocean, so excess/toxic sediment does not seem to be a problem. The presence of the oyster company could also negatively impact California harbor seal populations, which have their breeding grounds in the estuary (20% of CA harbor seal populations comes there to breed). The threat to seals is from human disturbance and the use of company motorboats rather than the oysters themselves—seals will react when humans come within 90 meters. However, this impact is not solely limited to the oyster company—hikers and kayakers could have a similar negative impact. And there are potential ways to mitigate these disturbance impacts, including the creation of large buffer zones or closing specific areas during breeding season (March-June).

California harbor seals

Oysters being transported in Drakes Estero

Colonial sea squirt (Didemnum)

One common complaint about the Drakes Bay Oyster Company is that it farms non-native oysters—the Pacific oyster from Japan (Crassostrea gigas). This species is now prevalent along the west coast, having been introduced in the early 1900s (for aquaculture purposes) after overfishing caused depletion of native Olympic oyster (Ostrea lurida) populations. Introducing one non-native species usually brings others—associated parasites and epibionts—and there is currently a large population of non-native colonial sea squirt (Didemnum vexillum) in Drakes Estero. As with any non-native species, the concern is that the population will reproduce on its own and expand, and may negatively impact (or out-compete) native species. This is a risk associated with the Pacific oyster itself, and the potentially expanding Didemnum population. However, it seems that at the moment, Didemnum is more of a nuisance than anything else, fouling marine equipment and, perhaps its biggest sin, being ugly.

As well as negative impacts, oysters offer significant benefits, both to the local ecosystem and economy. Oysters can increase water clarity by filtering up to 55 gallons of water a day—to put that in perspective, this is ~110 times what the average human drinks in a day, by an organism ~1/680 our size. In fact, many areas including the Chesapeake Bay are working on large projects to re-establish native oyster populations, both for economic and water quality benefits. One potential benefit of oyster aquaculture in Drakes Estero is that it could mimic the historical ecological benefits of the Olympic oyster (i.e. water filtration and creation of substrate habitat for fish and invertebrates). How well they might mimic the native oysters’ benefits depends on their relative abundance and biomass compared to historic populations of Olympic oysters (which is of course not well documented). But native oyster beds were likely integral to the original functioning of Drakes estuary, before they were destroyed by humans (an original alteration of the ecosystem). Which begs the questions… what is “wilderness”? What state exactly are we trying to restore? The “wilderness” of the early 1900s? Or some mythical wilderness of the 1500s that we can merely imagine (but that was managed, and altered, by Native Americans)?

Impressive historic native Olympic oyster reefs

So what is my final take on this issue? I’ve gone back and forth several times. The trade-offs, as I see it, are between deciding to preserve the land as wilderness, thereby prioritizing the value of nature and species protection, or trying to conserve the land while allowing multiple uses. Even full wilderness designation does not completely guarantee that animals will not be disturbed—the National Seashore gets over 2 million visitors a year, and the area relies on revenue from recreation. And there is the additional consideration of the economic benefits of the oyster farm, both in jobs and revenue. Without Drakes Bay Oyster Company, the Bay Area would have to import ~38,000 pounds more oysters each week in order to meet demand, which will in turn generate more carbon. Given all the trade-offs, minimizing the impact of the oyster farm through strict regulations, while allowing it to still provide important jobs and revenue for the region seems like it would be a good, and attainable, solution.

In the end, the decision about whether to close Drakes Bay Oyster Company is not a simple one. It’s a decision that has even divided avid environmentalists in the local community. It’s one of those decisions that should make us pause and re-examine what exactly we are trying to accomplish with designated wilderness areas. We need to protect natural areas for many reasons, but we also need to provide food and jobs for millions of people. And perhaps most importantly, if we want people to want to protect nature (a decision, I believe, that ultimately comes from the heart), then we need to live with nature.

Guilty pleasures: smoked salmon and unagi

Since it’s New Year’s resolution time, I’ve been pondering what this year’s resolution should be. Last year, I borrowed my husband’s idea of resolving to eat only “good” meat (i.e. organic, grass-finished, meat formerly named Polly/Charlotte/etc.). As a fisheries biologist, I try to do the same thing with fish by following the Monterey Bay Aquarium Seafood Watch recommendations. However, this can be hard when it comes to occasionally denying myself, especially two particular kinds of fish – salmon and freshwater eel (aka unagi to sushi enthusiasts). While wild Alaskan is a good option for salmon, many places (restaurants especially) carry farmed Atlantic salmon, which is better to avoid. And as for eel, I’ve been putting off (with dread, since I don’t think there are any at this point) looking into unagi alternatives.

Since my favorite food is smoked salmon—and since it also happens to be my study species—I’ve decided to look into the purported ills of farmed salmon. Smoked salmon at the grocery store is often farmed Atlantic salmon. But first, a quick aside to illustrate why this issue (e.g. finding good smoked salmon to eat) is so close to my heart. I was about 9 when I first read C.S. Lewis’s The Lion, the Witch, and the Wardrobe. In the scene when the White Witch offers Edmund any food he desires, he chooses Turkish Delight, and receives a bottomless tin full of (enchanted) confection. Since, at age 9, I had no idea what Turkish Delight was, I imagined a bottomless tin of smoked salmon – nothing could be better – and to this day, any mention of Turkish Delight automatically makes my mouth begin to water (and not for the candy). So, while I don’t think I’ve actually been enchanted, I find it about as difficult to resist buying a package of smoked salmon as Edmund found it to resist going back to the White Witch for more Turkish Delight.

Edmund fantasizing about Turkish Delight

Turkish Delight (a far cry from smoked salmon)

So what is wrong with farmed salmon? There are several problems with it, ranging from environmental impacts to serious health concerns. As with raising beef cattle, it takes a lot of food to raise meat. But unlike cows, which eat corn (well, not naturally, but that’s a whole other story), salmon eat fish, so there’s a large impact on the marine food chain. It takes about 3 pounds of other fish (mostly small pelagic fish) to produce 1 pound of salmon. In addition, many studies have found that salmon feed is highly contaminated with toxins, including PCBs and mercury, and this high toxin load gets transferred to the farmed salmon (at much higher levels than are found naturally in wild salmon populations).

Most farmed salmon, at this point, come from large aquaculture operations in Norway and Chile. In general, the salmon are raised in large netpens in near-shore ocean, a design resulting in pollution of ocean waters through fish and feed waste. Pens can contain up to 90,000 fish. Overcrowded conditions mean that disease and parasites run rampant, and can then be transferred to wild salmon populations due to the open netpen set-up. In particular, sea lice (a marine copepod) are a major concern (google image search them if you have a strong stomach—I couldn’t bring myself to put the pictures up on my blog). There have been studies showing the transfer of sea lice from salmon farms to wild pink salmon, causing infection and mortality in the wild populations.

However, there are some promising innovations in aquaculture that may mean better farmed salmon in the future. Closed, re-circulating systems prevent many of the environmental problems, such as pollution and disease/parasite transmission to wild salmon. There has also been some success rearing coho in freshwater pens in the US—these farmed salmon are now listed as a “best choice” by Seafood Watch (success!). In addition, innovations in net design are helping prevent some of the disease and parasite problems by using antimicrobial copper alloy netting.

So, after looking into salmon farming, I bit the bullet and did a little research on why freshwater eel are listed as “avoid” by Seafood Watch. After all, the first step to many things is knowledge. It turns out freshwater eel have a fascinating life cycle. They are catadromous—this is the opposite of anadromous (salmon’s life cycle), where the eels spend their life in freshwater, but go to the ocean to spawn. They find their way to rivers as small, immature, transparent eel (referred to as “glass eels”), and it’s at this stage that they are caught in droves in order to supply eel farms raising unagi. Basically, instead of raising eels from scratch (starting with eggs, as salmon hatcheries do), eel farms find it easier to go catch the young wild eels, and use these as a constant supply, thereby continually depleting already declining wild populations.

Glass eel, the life stage when they're caught to bring to eel farms.

Declines in wild eel populations

So, herein lies one of the hardest personal debates about being a good environmental steward. Do I completely deny myself a food I love, or allow myself to have it very occasionally? There is a fine balance between enjoying and living life, and also trying to live according to certain values. Where do you draw the line? As with purchasing carbon offsets for air travel, can we go out and do something proactive to protect fish populations every time we indulge in another round of unagi sushi? This is a balance I, and many people I know, continually struggle with.

What fish want

What do fish want? I thought I would try to focus on a seasonally-appropriate question, but also one that I spend a lot of time these days pondering. You might think that it would be simple to figure out what motivates a fish—after all, they probably aren’t influenced by the complex emotions that drive people. But unfortunately, we can’t just ask them (I have often wished for just one hour as a fish—I would learn… and publish… so much!).

In general, animal behavior is driven by a balance between the drive to maintain/gain energy stores, survive, and ultimately reproduce. So when asking why a fish chooses to inhabit a particular area of the river, we start by looking at the environmental factors (such as water temperature and shelter from potential predators) that might be influencing its behavior. In my research, I’m interested in what environmental factors are influencing juvenile steelhead behavior surrounding coolwater refugia (areas that are cooler than the main river, often because of an incoming cold creek). What causes fish to use coolwater refuges? And when the river is really hot, what causes fish to leave the refuge? In asking these questions, I’m hoping to gain an understanding of when these refugia areas are most important to fish.

Juvenile steelhead being measured

A heat image of a coolwater refugia area on the Klamath River (Image from U.S. Bureau of Rec)

Taking a step back… many rivers are getting hotter, both because of climate change (influence of higher air temperatures), and land use practices such as logging and agriculture. Logging the riparian area next to a stream reduces shading,  causing the water to heat up. Irrigation can lead to hotter water temperatures if water is diverted into shallow, slow-flowing irrigation ditches, then returned to the river. The Klamath River in northern California, where I do my research, can reach 80°F in the summer, which feels like bathwater. On cool mornings I would sometimes even get into the water to warm up.

Salmon are a coldwater fish, and prefer a temperature range of about 10-18°C (50-65°F). This means that during the summer, when the river temperatures reach 80°F, they are under serious thermal stress—the high temperatures increase their metabolism, so they struggle to maintain weight. As a result, fish will seek out areas in the river that are cooler, such as areas where tributaries flow into the river (i.e. thermal refugia). You can sometimes see hundreds of juvenile salmon packed into small coolwater refuges. However, fish sometimes leave the coolwater areas, even when the river is hot. Why? This question forms the root of my research.

Juvenile steelhead in a coolwater refugia area

I’m hypothesizing that it’s a trade-off between water temperature and the need to find sufficient food. While the fish gain a thermal benefit by hanging out in the cooler water, the high densities of fish suggest that there may be competition for food, forcing fish to leave for brief periods in search of prey.

To put this dilemma in a human perspective, imagine that it's 120°F outside, and you are in a nice air-conditioned house… with no food. You have the choice to go out and pick some food from the garden, or just stay inside and feel hungry. It’s a trade-off! At what point do you decide to leave? Now imagine that your body temperature changes to that of the outside temperature—so as soon as you walk out the door, your temperature begins to rise. This is what happens for fish, since they are poikilotherms—cold-blooded animals that do not stay in a temperature-constant environment, so their internal temperature varies over a wide range. While they are adapted to function over a certain range of temperatures, water temperatures may be rising more quickly than fish can adapt, leaving them with a shrinking amount of available habitat.

In order to understand when and where coolwater refugia are most important, we need to figure out what specific environmental factors are driving fish’s decisions to enter and leave refugia. To do this, I conducted behavioral field studies on juvenile steelhead at coolwater refugia sites on the Klamath River for the past 3 summers. I put radio tags into steelhead (see video below), and was able to track their movement and body temperature (pretty cool!) over time. So far, I’ve found some interesting effects of water temperature dynamics on the likelihood of fish using thermal refugia… stay tuned! (And to learn more about how I’m researching this, visit my website!)

Put in a larger (non-fishy) context, refugia habitats such as this will become increasingly important as the climate continues to change. Whether it’s a range shift upwards onto mountaintops for a high altitude terrestrial species, or a fish seeking out cooler water, understanding how animals use refugia and when they are crucial to their survival will be an important aspect of preserving some species.

And now, if you’ve made it this far, enjoy the holidays! I, for one, will be enjoying a taste of the fruits of my labor.

A river running free

Last week I went on a hike along the Elwha River in Olympic National Park, Washington. Not only was I excited to get out and hike (which happens far too infrequently these days), but I wanted to see the Elwha now that it’s a completely free flowing river again. The largest dam removal in the world just took place on the Elwha—the two dams that were located 5 and 13 miles upstream of the Strait of Juan de Fuca are now almost completely gone.

Glines Canyon Dam before removal

Glines Canyon Dam as of 11/6/12

 I hiked through the mossy dripping rainforest up above where the dams had been, imagining (or, let’s be honest, hoping) that I would come across Bigfoot around the next bend and make my millions. The ecosystem there is incredibly verdant — temperate rainforest that gets approximately 150 inches of rain annually—with towering Douglas firs, dripping alders and Bigleaf maples, and plenty of mushrooms pushing their way up through the mossy ground. I kept my eye out for Oyster mushrooms, but no luck. I also stopped frequently to scour the turbid water for salmon, since both Chinook and Pink salmon, as well as steelhead, have already been sighted upriver of the lower dam! (Granted, it would be surprising to find them above the upper dam, which is not yet completely gone… but as with Bigfoot, one can hope).

Olympic National Park forest

... Bigfoot?

 While I am a firm believer in ecological restoration, there are not many restoration stories that have brought tears to my eyes, but hearing that salmon are already returning to parts of the Elwha that have been inaccessible to them for the past century did literally make me tear up. It’s also a nice example of how dam removal can be successful. A few months ago, my friend asked me, “Is dam removal good?” A great question! She had been at a party and gotten into a discussion about dam removal. As a scientist and someone generally in favor of ecological restoration, she felt intuitively that dam removal is a good thing, but when asked why, she wasn’t sure. What really are the benefits of taking out dams? To emphasize the importance of this question, you should know that there are about 75,000 larger dams (over 6ft) in the U.S., and an estimated 2 million total. However, most of these were built with only a 50-year useful life-span, and the number of “high hazard dams” in need of either reinforcement or removal is rising sharply.

Map of major dams in the U.S.

 One of the many exciting aspects of dam removal (and one close to my heart) is the benefit to anadromous fish, such as salmon. (Anadromous fish begin life in freshwater, travel to the ocean to grow, and return to the river to spawn). Salmon rely on large amounts of high quality river habitat for spawning, juvenile rearing, and migration. Large dams without fish ladders are impassible to salmon, cutting off enormous amounts of good river habitat. And the habitat that’s left is often lower quality, in terms of temperature (too hot) and sediment composition. Dams block sediment, meaning that lots of fine sediment that naturally flows downriver is blocked behind dams. The result is that you get huge sediment build-ups behind dams (there are 5 billion tons of sediment behind the Glen Canyon Dam!). The downstream impacts of this sediment blockage include a coarsening of the riverbed sediment (since all the fine sediment is trapped upstream), which decreases the amount of good spawning habitat for salmon. In addition to the impacts on salmon, the lack of natural sediment flow has caused substantial beach erosion, since this sediment is what beaches are made of (California beaches are being reduced by ~2.8 million cubic meters of sand per year). 

Towards the end of my hike along the Elwha, I made my way down to the large rocky expanse where the upper reservoir used to be. It was sobering to stand on the bank of what is now a flowing river, and realize that only a year and a half ago, I would have been deep underwater. The floodplain hasn’t reconnected with the river yet, but with the river’s natural flow regime restored, this should happen in time. (Dams drastically alter a river’s flow regime—the pattern of water flow over time—usually by homogenizing it, so that the water flow doesn’t change much throughout the year.) One of the less widely known benefits of dam removal is the restoration of the flow regime. The animals and plants along a river evolve to take advantage of that particular river’s flow regime. For example, cottonwoods time the release of their seeds with floods, to aid in dispersal, and aquatic insects such as caddisflies synchronize their metamorphosis (from aquatic insect to terrestrial adult) with the average timing of flood season. When flow regimes change drastically over a short time period, as happens when a dam goes up, it can be hard for these species to adapt.

Glines Canyon reservoir bed from the air

On my hike, standing in the Glines Canyon reservoir bed looking downstream

As I’m reminded daily through conversations with my husband, there’s a lot of controversy surrounding dam removal. I’ve seen my share of this during my summers doing research on the Klamath River, where the 4 lowest dams are scheduled to come out in 2020. Many people want to keep dams because they are a symbol of progress (at least, the Greatest Generation feels this way), and because they like boating and fishing in the reservoirs. However, since many of America’s dams are old, it’s worth considering the fact that it may be more beneficial (ecologically and economically) to remove than to restore them.

A sign from near where I work on the Klamath River

Another sign from near where I lived...

There’s a lot more to learn about dam removal, but I hope I’ve given you a few good points to fall back on if you find yourself defending its benefits at a party. And if you haven’t seen it yet, you really need to watch this spectacular video of another Washington state dam removal, the Condit dam on the White Salmon River.