Some people are fortunate enough to be passionate about their jobs. They
are also probably familiar with the roller-coaster love-hate relationship that
comes along with this passion. This is especially true in grad school, where
passion for your (often outdoor) research is then traded for long hours at the
computer, doing data analysis and statistics. And I’m one of those people that
thinks statistics is fun, but after hundreds of hours, I’m often in the “hate”
phase of the roller-coaster. The solution? A week-long course explaining the
guts of statistical models, held in a spectacular location, that can re-ignite
your faith in statistics and even broaden (if possible) your love of nature.
This past week I took a course in mixed effects models, which happened
to be located in Banff, Alberta. (I had to convince my advisor that this was
not the reason I signed up for the course.) Banff is as spectacular as the hype
might lead you to believe – it reminded me of a cross between leafy-green New
England and Aspen Colorado (but with more epic-looking mountains). I had,
without doubt, the most amazing few days of wildlife viewing of my life. I
headed up to Moraine Lake at 5a.m. one morning for some dawn photography with
a friend from the modeling course, and in quick succession, we came across a
porcupine, 5 Snowshoe hares, 2 pika, and the incredibly elusive wolverine, an
animal that I never really expected to see in my lifetime. I saw its dark
shaggy back disappearing into the underbrush, and then it was gone.
On the Bow River, north of Banff
A gray dawn at Moraine Lake
We spent daytime hours in a sort of endurance-learning fiesta – like
drinking from a fire-hose, as one girl put it – absorbing as much statistical
knowledge as possible while it washed over us in voluminous waves. But luckily
it was light from 5am-10pm, and we were able to explore before and after class…
and sometime during these days in Banff, I re-discovered my interest in birds. I’m
not sure why I’ve never really taken to birding – my husband is a birder, as
are many of my friends (one of whom is so enthusiastic that he plans to tattoo an
image of the 600th bird he sees onto his butt). But the fact is, I’ve
had only a passing interest… until this trip. Perhaps it was seeing the Great
Gray Owl close-up in a meadow one of the evenings, staring at us with
yellow-eyed suspicion, a bird I’ve been obsessed with seeing ever since
listening to its incessant evening hoots while living in Yosemite. Or perhaps
it was the early morning trip to Moraine Lake, where my birder friend was able
to pick out species after species from the dawn cacophony of calls, a language
he spoke but I didn’t. Regardless, my interest was piqued.
And really, when you think about it, why isn’t everyone obsessed with
birds? They are brightly-colored animals that FLY and are related to dinosaurs. Perhaps it’s a matter of novelty. If
birds existed only in Africa, we’d probably all be dying to take a bird-safari
to go see the colorful flying mini-dinosaurs. Who cares about lions!
So I spent my 3-days of backpacking in the Banff wilderness with
binoculars in hand, re-discovering the joy of stop-and-go hiking as I birded my
way along the trails. Incidentally, it helped my birding skills considerably
that I didn’t fall into my usual zone-out hiking style, due to the fear of a
grizzly round every bend. That’s pretty good incentive to stay alert. (It’s
also surprisingly hard to keep up a steady stream of whistling while hiking
uphill.) My birding efforts were rewarded by many cool species (see below), among
them a Ruffed Grouse that I nearly ran into, perched silently on a branch by
the trail. (Thankfully, since my only experience with Grouse has been as a
master of camouflage, staying perfectly still until you’re right on top of it,
when it explodes from the underbrush with a thunderclap.)
And so, like a meditation retreat, grad school-style, my week of
re-inspiration is complete. It’s hard to write engagingly about statistics, but
I’ll say that mixed effects models are immensely important for ecological
analysis, since they allow you to take into account (rather than ignore) individual
variation… which is pretty much a given in ecology. And for my data, which
features 200+ fish all behaving slightly differently, this is a definite
necessity for teasing apart any patterns. Data analysis, here I come (again).
Banff wildlife bonanza (e.g. all the species I saw during my trip):
A few weeks ago, I had the opportunity to help out a labmate with her research
on the Mokelumne River (and take a classic fish photo.) Unfortunately, I didn’t
catch it angling… an electro-fishing boat caught it. For those who haven’t
heard of this, it’s a boat that sends out pulses of electricity through the
water to momentarily stun fish, a common way to catch them for fisheries
research. Cheating? Perhaps. But the fish aren’t hurt, and it’s a whole lot
easier (though less fun) than fishing all day to catch your sample size quota.
Striped bass classic shot
E-fishing boat courtesy of collaborator EBMUD:
the hanging metal cables shock the water
We were up on the Mokelumne, which joins the Sacramento-San Joaquin Delta
near San Francisco, to remove all the striped bass from a pool below an
irrigation dam. California’s Sacramento-San Joaquin Delta is plagued by many
problems, and foremost among them is the conflict over water needs between
agriculture and ESA-listed native fish populations, including salmon,
steelhead, and Delta smelt. As a result, a lot of effort goes into trying to
figure out what is causing high mortality in native fish populations, and what
can be done to boost survival. One possible culprit: striped bass.
The last thing the juvenile salmon sees (looking down the striped bass gullet)
Striped bass are native to the Eastern U.S., and were introduced to
the west coast as a game fish, a sadly familiar story. (As an interesting
sidenote, Wikipedia lists many common local names for striped bass, including striper,
linesider, rock... and my favorite, pimpfish). Striped bass eat juvenile salmon
(see my post from last October), so one suggestion for boosting salmon populations
is to decrease predation pressure by attempting a large-scale striped bass
removal, through unlimited fishing allowances. But will this work?
My labmate is looking at an interesting aspect of this question. She
is measuring juvenile salmon mortality as the fish move past an irrigation dam,
both when striped bass are present in the pool below the dam, and when they are
absent (through removal). The idea is to see if salmon mortality drops
dramatically when the bass are absent, or if other predators in the system (some
of them native, like the pikeminnow) fill the predatory niche, making removal ineffective…
or perhaps even exacerbating the problem, since striped bass also prey on some
of the other fish that eat salmon. If striped bass are removed, this would
release these other predator populations from bass predation pressure as well,
and could potentially cause a sharp rise in other predator populations. (For a
more complete, interesting discussion of this topic, check out well-known
fisheries biologist Peter Moyle’s post on the California WaterBlog).
The fieldwork for this project was quite fun, involving many slippery,
spiny fish and a beautiful day in the California sun. I joined in for the bass
removal day, so a group of juvenile salmon had already been released through
the dam the previous day and mortality measured while striped bass were
present. We were there to remove most of the striped bass, prior to another
salmon release. To remove striped bass from the pool, an electro-fishing boat made
four passes through the pool below the dam, shocking the water and catching a
cross-section of the fish community each time. Striped bass key in on pools
below dams, where salmon coming through are funneled through a small area in
large numbers, providing an easy feast for waiting predators, so this pool is
usually full of bass around this time of spring, when juvenile Chinook are
out-migrating to the ocean.
The irrigation dam and pool
We took striped bass diet samples to get an idea of what proportion of
the bass diet is made up of juvenile salmon. This is done through gastric
lavage (aka making the fish barf by flushing them out with water). The only
downside to this is that the spines on the dorsal fin of striped bass are
surprisingly sharp, and fish are slippery and wiggly. Suffice it to say that I
got some war wounds.
Barfing a fish
One striped bass' breakfast
We then returned all other fish species to the pool, but retained the
striped bass and transported them to another river later that day. It will be
interesting to see the results of this research. However, I doubt very much
that removing all striped bass from the Sacramento-San Joaquin system will be enough
to cause significant increases in salmon populations. The Delta is a highly
altered system—it used to be an extensive wetland, and is now mostly
agricultural fields and channelized habitat—so extensive habitat restoration will
likely be needed to help restore native salmon populations. However, this is a
complex question that deserves its own post. Stay tuned.
But predator removal could well be a part of the solution, and
hopefully this study will help us determine whether this is true. Striped bass
for dinner, anyone?
The crew (fish and human)
And most importantly... when you're doing fieldwork in the sun all day,
you have to be innovative about how to keep the chocolate snacks from melting
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.
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 27th 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.
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.
