Where Do All the Fish Go?
I hope absence makes the heart grow fonder. After a long hiatus, I’m back with another research update. And, I have to say, it might be the most interesting (and hopefully most influential) project I worked on for my Ph.D.
But, first, let me set the stage for those of you who may be new to this blog. I work on brook trout ecology in the Loyalsock Creek watershed in Pennsylvania. The watershed is mostly forested, making it a great home for my Ph.D. research on brook trout population response to climate change. I’ve previously reported on other findings from my research showing that interbreeding between wild and hatchery fish was fairly minimal throughout the watershed and also some preliminary telemetry results showing that some brook trout seem to move from the small tributaries into the mainstem river after spawning season.
But, the question always remained, what happens to fish that get into the mainstem? There are a lot of predators in the mainstem and water temperatures in the summer far exceed brook trout thermal tolerance. So, many speculated that fish that got into the mainstem probably died within a few months. Moreover, our telemetry observations only found that a handful of fish seemed to have this migratory behavior. So, even if they did survive, could their behavior really drive any sort of population-level response?
The answer is a resounding yes.
I’m basing that response on a study we (myself, my advisor, and very importantly a collaborator in the statistics department) just completed that looks at genetic connectivity of brook trout populations across the Loyalsock Creek watershed. As you may recall from previous posts, maintaining and increasing connectivity among populations is one of the most important management tools we have for increasing population persistence and resiliency to future disturbance. And, we can measure the degree of connectivity between two populations by measuring the degree of genetic similarity. This isn’t so hard- we take a little fin clip from a bunch of individuals in each population of interest, from the fin we identify the genes present in each population, and then using some computer software we estimate the degree of connectivity.
Knowing if two populations are genetically dissimilar- and thus disconnected- is great, but it doesn’t necessarily explain why those populations are isolated from one another. Sometimes it’s easy. If there is a large waterfall that separates two populations, then it’s reasonable to assume that few individuals are moving back and forth between those populations and therefor connectivity is low. Other times it’s not so clear. There could be a hidden barrier (perhaps a road crossing with bad fish passage or an area with a steep slope), or it could be that our assumptions about what limits fish movement (and thus population connectivity) are wrong. That last point is important, because if we don’t know what we are looking for then we will never be able to identify and fix areas of stream that are reducing population connectivity or conserve areas that are important movement corridors.
So, we used some really fancy models (hence the phone-a-friend to the stats department) to essentially determine how various features in the watershed either resist or increase gene flow. We call this a riverscape genetics study- essentially seeing what features of the riverscape (which is like a landscape, only for streams and rivers) are responsible for producing the observed patterns in genetic connectivity. And, remember, individual fish are just bundles of genes, so this analysis is a proxy for determining which features of the watershed increased and decrease fish movement.
To run the analysis, we identify a bunch of variables we think could influence gene flow, and then let the model tell us whether there is actually a high probability that gene flow is influenced by each variable. So, we thought about it and decided to include 12 variables. This included some of the usual suspects like stream slope, road crossing density, and large barriers (like waterfalls), as well as some more unusual variables like distance to mainstem Loyalsock and a few things that essentially measure the location of a stream within the watershed. After it was all said and done, we found support for just four variables that influence gene flow in Loyalsock Creek, including:
Why am I so excited bout this study? First, for any fish biologists reading this post, the model we used is new, and I’m hoping it provides a framework for future riverscape genetics analyses (so, contact me for details!). Second, and most importantly, it definitively shows that the mainstem is not only brook trout habitat but may be some of the most important brook trout habitat in the watershed. Because larger rivers are thermally unsuitable for coldwater fishes during summer and don’t have large resident trout populations, they generally don’t receive the same conservation status as small tributaries. However, these rivers are critical migration corridors that are responsible for increasing population connectivity.
This study also gives some insights into how future disturbance could influence brook trout population connectivity. With climate change we are generally expecting increased floods and droughts- both of which will change stream flow patterns and could limit the ability of brook trout to move through the mainstem. This is particularly true given that there is only a small window of time where thermal conditions are suitable for brook trout to use the mainstem, and so disruption of flow for even a short period could have large effects on trout populations. Additionally, human disturbances that alter flow patterns, either through direct water withdrawals or watershed disturbances that result in a lowering of the water table, could influence flow patterns in larger rivers as well as increase the periodicity of flow in intermittent stream channels. So, if we want to maintain future brook trout population connectivity, we probably need to start thinking beyond just removal of physical barriers and conservation of natural stream flow patterns.
Finally, a word of caution. This study was conducted in Loyalsock Creek and, while some of the findings likely do translate to other watersheds, I would expect the results to change depending on the location. For example, as a largely undeveloped watershed, variables like road crossings and watershed development were not important for explaining population connectivity. These features undoubtedly influence brook trout populations, they are just uncommon in Loyalsock. But, I’m looking forward to this model being applied elsewhere and seeing how the results change across watersheds.
The Story of a Wayward Wander
That’s a wrap, folks. In just a few hours the clocks will strike midnight and for the next several weeks I’ll write the incorrect year on every document I sign.
This week my computer has been busy running a very long genetic analysis. Notice I say my computer was busy- it took about five minutes for me to start the analysis, but it’s going to take close to two weeks for my computer to churn out the results. And, while new and upgraded, my computer doesn’t have enough oomph for me to run other programs while genetics voodoo happens in the background. Luckily, this was just a trial run. Eventually I’ll have to do a much more extensive analysis that will take even longer to run. I can’t wait.
I’m always a little nostalgic on New Year’s Eve. Sure, I could be wishful and think about all my resolutions for 2017. But, let’s be honest. Those are empty promises. I won’t read or vacation more, it’s unlikely I’ll get back to running a 10k a week, and I just don’t have the self-control to be less grumpy. But, 2016 still holds some magic. It’s like a story where the last line is about to be inked and the chapter closed. We survived another one, and there’s no better way to spend this day than retelling the story of 2016 with some pictures I never got to share.
If I’m telling I story, I think it needs a title, and I think “Wayward Wanderer” captures the essence of 2016 pretty well. I traveled. A lot. And I didn’t have any idea what I was doing most of the time.
In January I was finishing a three-month stint in West Virginia where I was collaborating with the USGS Leetown Science Center. Using their experimental stream lab, we were mimicking climate change to see how individual fish differed in their response to rapid increases in stream temperature. I’ll report on those data eventually, but suffice to say fish aren’t swimming robots and do react much differently from one another. We are exploring the data to see if we can figure out if some fish are predictably better than others at tolerating increases to temperature, but it will be awhile before we get that data.
While in West Virginia I got snowed in under 43 inches of snow, and then less than a week later I was on a plane headed for Panama City, Panama. I volunteered to help someone else in my lab with their fieldwork, which entailed a six-week trip to the rainforest. I can still remember sitting on the plane, taking off from Richmond, Virginia thinking to myself “what have I got myself into.”
And, to this day, I still don’t really know what I go myself into. I’ve done a lot of field work, but nothing prepared me for that experience. Hiking miles upstream to remote sample sites that few people in this world had ever seen, spying on howler monkeys, getting surprised by boars while collecting data, and of course the snakes. So many snakes. It felt like a real life nature documentary. But, it wasn’t just about the science. I was living along the Panama Canal in a small neighborhood shared among canal workers and a handful of other American scientists who are some of the most intelligent and fun people I’ve ever interacted with. Some days were spent roaming the streets of Panama City trying to remember enough Spanish to order food and find my way around. It was an experience that will no doubt rank among the most memorable times I had while in graduate school.
Leaving Panama was bittersweet. After six weeks I had grown a little tired of watching out for dangerous creatures (I came within inches of stepping on a fleur de lance, one of the most venomous snakes in South America, and had a caiman lunge at me from the banks), and I was there at the height of the Zika scare. Someone on my field crew even contracted the disease, and I was working on a species of fish that feeds on mosquito larvae. But, I wasn’t ready to say goodbye to the cultural and social experience. Plus, as long as I was there, I didn’t have to worry about my own pending field season.
But, all good things must come to an end and in mid-March I boarded a plane back to the United States, spent an unexpected night with the pigeons of the Newark airport (seriously, Newark, get it together), and then finally got back to State College. I had a little over a month to apply for permits, finalize field sites, organize crews, buy supplies, etc. And, within hours of getting back to the office, we were awarded a grant to work on the gene expression project that is now showing early promising results. So, I also needed to work on my poker face, because I had no idea was I was doing. Like, zero clue. I had never done telemetry or tissue sampling, had no real idea how the fish were going to behave, nor, honestly, did we know if the fish would survive everything we were doing to them. While I had a long list of people that could provide guidance with a few pieces of the puzzle, I felt the pressure to make it work.
And I did. Usually. Telemetry officially started in early May and for seven months I felt like I was making it up at I go. But, as normally happens, the things you stress out about the most turn out to be the things that aren’t that difficult. Tagging and sampling? Psss…a breeze. And the fish survived. But, tracking every day? That turned out to be a bit harder. It shouldn’t have been a surprise; field work is a long string of judgement calls that can make or break your entire project. The longer you are in the field, the more of those calls you have to make. No pressure, right? Things like should I wait the rain out, is it really too dark to keep going, are flows too high to wade, should I dig after this tag that seems to be moving in the bank? There’s a fine line between good data collection and stupid data collection, and it takes practice to find it, flirt with it, and ultimately make good calls. While I have a few years under my belts, I always feel guilty and think I could have done more or better.
Ultimately, the biggest hurdle with telemetry was the mental game needed to stay engaged and committed. I walked the exact same streams every day tracking the same fish, often to the same exact spot. Every day. For seven months. But we made it- through dropped tags, harsh weather, wildlife encounters, human encounters, and broken bones. And, I think we got a great dataset. And, now that I’m on the other side of the hurdle, I think back to all the times I was standing beside the stream, tired and wanting to call it a day, but took a deep breath and continued on. Stubbornness is one of my best properties, and it helped that Savannah, Dan, and David kept me entertained.
During telemetry I basically lived in Loyalsock where phone service is non-existent and internet is sparse. It made communication difficult, particularly in summer when I was working on publishing a manuscript (which was finally accepted, woohoo!). But, as an upside, it’s a great way to disconnect and motivation to work hard during the day to guarantee an early bedtime. But, I was still largely living out of a suitcase. I think I packed in November 2015, and it wasn’t until September 2016 that I fully unpacked, bought perishables from the grocery store, and enjoyed a full week at my apartment. Even then, I was still making regular trips to Loyalsock, a 4-hour roundtrip commute, so I was still a stranger to the office.
Telemetry season ended in November, and since then it’s been more travel, only this time to spend holidays in Virginia with my ‘research assistant.’ As the year comes to a close, we are working hard to analyze and publish data for the genetics of brook trout in Loyalsock. Where will we go after that? Your guess is as good as mine.
Finally, perhaps motivated by lack of communication and entertainment this summer, but mostly interactions with interested anglers and citizen scientists, I started this website in June. I didn’t really know what to expect, but I can say the response has been far more receptive than I imagined. In less than six months this website has gotten nearly 17,000 views. Most importantly, it has connected me to people with questions about stream ecology, organizations like Trout Unlimited, news stations, and other academics. I also received an award for scientific communication. So, thanks to all of you for joining me on this ride, and I’m looking forward to seeing where it takes us in 2017.
So, did I earn my paycheck this year?
To the Day I Never Thought Would Come
I made it- 168 days after I released the first tagged trout back to Loyalsock, I am hanging my waders up to dry. Telemetry season 2016 is over. And, it a good one.
Here are a few quick numbers to describe the last 6 months.
What’s on the docket now? First off, a lot of sleep. Then, a lot of unanswered emails. “I’m in the field” has been a great way of avoiding a lot of requests and obligations. Thankfully most people emailing me understand the chaos of field season, but I can no longer play that card.
After that, it’s time to start thinking about how to analyze all the data. In addition to the telemetry study I have about three other projects that are in need of attention. The data for all of them are collected, the results fairly clear and predictable, but it’s time to start making them more official and getting them ready to publish. For example, I can tell you a lot of great information from what I saw in the field. But, rather than saying “the fish moved,” I need to relate movement patterns to things like stream flow, fish size, and hopefully genetics. To do that, I also first have to clean all the data- fix bad GPS points, download temperature data, make sure everything is recorded correctly, etc. A lot of mind numbing days are ahead. But, sneak peek- the fish moved. And the most surprising thing, at least to me, is how many fish moved to Loyalsock after spawning. We thought it might happen, but I was thinking it would be a smaller percentage than what we found. During November sampling we really struggled to find adult brook trout, while in September they were plentiful.
While I’m looking forward to spending more time at the office and having some resemblance of a normal schedule back, it won’t take long for me to miss Loyalsock. While the bulk of field work for my degree is now complete, we have discussed the possibility of sampling more in the spring and summer. So, hopefully it won’t be too long before I’m back.
For now, Happy Thanksgiving! And if you’re fishing Loyalsock, keep an eye out for my antennas. My babies are on their own until spring.
The Little Trout That Could
In 2014 it was a hunch.
In 2015 it seemed like a long shot.
In August it was wishful thinking.
In September it seemed possible.
But today it is without a doubt confirmed. Brook trout use Loyalsock Creek as overwintering habitat.
In my post last week I hinted that this was probably the case. There were a few tags that suddenly appeared in the mainstem shortly after what I had guessed was peak spawning season. But, we couldn’t be sure. There’s always a question of whether a dropped tag floated downstream. And, even with some tags entering the mainstem and going upstream, it’s always possible that they were gobbled up by a bird.
But, there’s no question about it now. This week we’ve been doing the final round of 2016 tissue collections and finished a little early on Thursday. On a wing and prayer, with daylight dwindling, I sent the crew to an area on the mainstem Loyalsock that had a few tags and was shallow enough to wade through. I was hoping to maybe move the tags around, which would confirm that it was in a fish, and with any luck actually capture a brook trout. But, even if a trout was there, the probability of catching it was small. Backpack shockers are intended for small streams where you can push fish into habitats they can’t escape. In larger waters, the fish feel a little tingle and start running. And, walking in Loyalsock is like sliding around on greased bowling balls. But, I had to try.
So, Dan and I hoisted on the backpacks and started shocking. Chubs, madtoms, smallmouth bass. All signs of a cool water fishery and not what you want to see in trout waters. We shocked past where the receiver said the tag was, but it didn’t move. It started to seem likely that it was a drop. We fine-tuned the signal to a large rock and Dan started shocking all around it. I stood on the side anxiously awaiting the outcome and prepared for disappointment. Standing there, I see a white mass come out from under the rock and held my breath in excitement waiting for Dan to identify his catch. Sure enough, not only was it a brook trout, but it was tagged fish 38.16. Success! And, after searching for more tags, we ended up catching a much smaller, untagged brook trout. They are there, and they are fairly abundant.
That fish was originally tagged in East Branch in September. In the early weeks of fall tracking we saw it swimming in a shallow pool several times, likely preparing to spawn. And then it disappeared. Based on my experiences this summer, that usually meant that something had eaten the fish and taken the tag far away. But, in the days that followed I noticed tags go “missing” at a much faster pace than I ever saw over the summer. Looking to rule out possible downstream movements, I tracked Loyalsock one day. Sure enough, there they were.
Now that we are nearly at the end, I can confidently say over 1/3 of fish tagged in September moved into the mainstem Loyalsock (and that proportion might be much higher once I determine how many tags were dropped in the stream. And, I’m sure more are on their way. There are a few fish that have been moving downstream in the past week and are probably on their way to Loyalsock now.
Tributary to mainstem trout movements are not as uncommon as you might think. And, though only a handful of studies have documented this movement pattern, it makes a lot of ecological sense. Coming off of a stressful summer and increased activity with spawning, adult trout are literally starving. And, they know that they need to prepare for a long, cold winter ahead. In the winter fewer insects are emerging and the once bountiful streams lack significant sources of food for trout. But, mainstem rivers have many small fish that are not only plentiful, but have a higher caloric value than small insects. In fact, during sampling the last two days we found several trout with small trout tails hanging out of their mouths. Diets once made almost entirely of insects have quickly shifted to fish-dominated.
The mainstem also offers some thermal buffer relative to the smaller tributaries. As stream temperatures continue to drop, trout will enter into periods of dormancy known as torpor. Trout don’t actively choose to go into torpor; it’s a physiological response to cold water because, unlike humans and other endotherms, fish cannot maintain their body temperature. Their body temperature is the same as the water they are swimming in, and when they are cold their muscles don’t function as quickly as when they are warmer.
Torpor is likely, at least in part, an evolutionary response to a lack of food. While in torpor, fish metabolism is very low and they require very little energy to remain alive. However, while torpor may allow fish to survive cold winters, it also decreases their ability to continuing growing and reduces the amount of energy they can put towards producing offspring. But, by staying a little warmer during winter, fish occupying mainstem rivers will spend less time in torpor, more time feeding, and they can put more energy into growth and reproduction.
So, in short, trout migrating to the mainstem have more food sources, grow larger, and maybe even produce more and healthier offspring. More interesting, though, is that only a subset of the population seems to engage in the behavior. Some seem hardwired to do these movements, and others content staying in the small streams. What causes this? Great question, but I have no idea. At least not yet. I still have over a year to figure it out.
A New Tagging Season
The lazy summer days of tracking just got a giant kick start. That’s right; fall telemetry season is upon us. This week we finished tagging 61 brook trout and also collected tissue samples from nearly 150 other fish for genetic analysis.
In an earlier post I walked through the step-by-step process of telemetry tagging. Reading that post now, I feel like it’s a bit of a misrepresentation of the tagging process. The methods are accurate, but it doesn’t do justice to how exhausting the process is. So, what does a tagging day actually look like?
For starters, there are a lot of batteries. And, no matter how good my intentions are to start charging those batteries early the day before sampling, it never happens. Same goes for running odd errands, packing miscellaneous supplies, and making sure everything is labeled. I can start these projects weeks in advance, but it won’t be until the day before that they actually get done. Often this is no fault of my own as I’m waiting for supplies to arrive from collaborators or details to be finalized. Either way, I go to bed far too late. I’m off to a great start.
It’s tagging day and the alarm greets me at 4:15am. I think ‘how much do I really want this degree?’ as I roll out of bed. I’m a morning person, but this really pushes my limits. I quickly make coffee and start hauling all of those supplies back to the truck. Thankfully State College grocery stores are open 24 hours, because I still need to get ice for tissue samples (side note: stores may be open that early, but by no means do they expect any customers to be shopping - many looks of insanity are received).
By 6am I’m at campus to meet anyone from Penn State joining me for the day. We throw everyone’s gear in the back and start the two-hour drive to Loyalsock.
We arrive to the site around 8 where we meet a small army of volunteers that have thankfully given up their day to help. Everyone waders up, and we start hauling the entire contents of my truck to the processing station. It takes about 30 minutes to get everything set up and I signal the electrofishing crew to start.
From there my day becomes a juggling act. I’m trying to keep the electrofishing crew moving, but they can’t catch too many fish because I need to collect tissue samples within 30 minutes of capture (after 30 minutes protein levels, the primary thing we are analyzing, in gills and blood change). I’m taking biopsies and tagging fish. But, almost every fish is a judgement call- tag a smaller fish now, or wait until later in the day when we might catch bigger fish but risk running out of stream. We are also trying to recapture fish that were tagged in May, so I’m trying to remember where they are and their tag IDs so the crew can focus effort to a specific place. But, “next to the big tree” isn’t very descriptive to someone that hasn’t been walking the stream all summer.
My job is mentally exhausting, but I barely move from the processing station all day. The electrofishing crew is constantly on the move. One person is wearing a 30-pound electrofishing backpack. The others are carrying heavy 5-gallon buckets of water and fish. Everyone is walking (more like controlled falling) over the equivalent of oiled bowling balls. As soon as they catch a fish, someone has to hike it to the processing station which can be up to half a mile away (recall the 30-minute time window). At the processing station, they set the bucket down, grab an empty one, and hike back to the electrofishing crew. No rest. I have the greatest volunteer crew around, otherwise this would not happen.
We typically finish sampling around 6pm, but the day is far from done. All the fish that we caught are still recovering in nets next to processing and need to be dispersed across the stream. While the new tagged fish are placed somewhat randomly in areas of good habitat, recaptured fish that were tagged in the spring need to be returned to the exact place they were captured. So, everyone grabs a bucket of fish and we start hiking. This week we also added plasma collection to our repertoire (because obviously not enough was going on). To collect plasma, every blood sample needs to be centrifuged for 5 minutes, plasma pipetted off of red blood cells, and then both blood components processed and put on ice. At this point, daylight and patience is growing thin.
We leave the site around 7pm and start the two-hour drive back to State College. I drop everyone off at campus and make a quick detour to my lab where I organize blood samples and place everything in a -110° F freezer. Finally, nearly 16 hours after I left, I make it back home around 9:30pm.
But, remember all of those batteries? That’s right; they all need to be brought back inside to charge. New vials need to be organized and labeled, supplies repacked, and an email sent to the volunteer crew meeting us the next day so they know where to go. Inevitably, something always breaks during the day, so I need to fix or troubleshoot the problems. Finally, around 10:30pm, I’m at least somewhat prepared for the next day. Despite only consuming coffee all day, I really question whether I want to eat dinner or go straight to bed. I opt for food, but only because I can hear my mother in the background scolding me for poor eating habits.
My head hits the pillow around 11pm, and the process starts all over. This time, not only am I waking up to question my desire to graduate, but also wondering just how sore muscles can get.
What the Summer Taught Us
Weather permitting, next week we will start the last major round of brook trout telemetry tagging. The end of this project is still several months away, but the close of summer means there is light at the end of the tunnel.
I can also rest easy now knowing that this summer “worked.” It wasn’t always easy, and there were plenty of surprises along the way, but there is a generous dataset sitting on my computer ready for analysis. Since May, I, along with one technician, have amassed 1,497 detections. Every single dot on that map represents a telemetry growth pain, including:
Tagging fish less than 6.5 inches will, without question, result in you spending hours on the side of the mountain trying to recover a tag from a fish that has been predated on. If you’re lucky, the predator will have only carried it to the adjacent hillslope. Often times it will not have spared your soul and you will find yourself hiking miles through a rocky river with snakes.
Lesson learned: only tag big fish. They probably have the most interesting movement data, anyway.
If there’s a section of stream with bad access, the fish will find it. Not only will they find it, but they will love it.
Lesson learned: If your first assessment of a stream is that it’s merely ‘doable,’ immediately delete it from the candidate list. Hiking over rocky outcrops and crawling through downed trees will get old long before the study is over. Relatedly, when tagging, you need to capture every single fish that has ever thought about swimming in the stream. Otherwise, you will have electrofished one mile of stream before running out of tags. Inevitably, those fish will move upstream, making the length of your study area obnoxious.
Telemetry is simultaneously the coolest and one of the most boring methods of data collection I have participated in. I am monitoring the decision-making processes of an iconic fish species. But, after about the third week I had memorized their exact locations and then continued to confirm that I had memorized them about 1,200 more times. And, I’ll keep doing it for the next three months. Fish movement doesn’t break the cycle, either (see above lesson).
Lesson learned: Starbucks might as well be a collaborator. And, sometimes the best skillset for a technician is having a lot of stories to tell.
A tagged fish and a dropped tag can have nearly identical behaviors. Also, tags can drop at any time during the study. As a result, your dataset becomes a series of emotionally charged messages where one day you were excited because the tag surely seemed to be moving. Then, less than 48 hours later, you find it floating on the stream bottom.
Lessons learned: Never get your hopes up with field work. And, invest early in a snorkel. It makes is much easier to recover dropped tags, thus maintaining a high baseline level of frustration.
Fish are incredibly resilient. With light sedation we can collect blood and gill samples and perform a fairly invasive surgery. Minutes later the fish is back in the stream feeding. For humans, this would be the equivalent of taking half a sleeping pill before getting a lung biopsy, having a 30-lb weight stitched into your abdomen, and then being expected to run a marathon.
Lesson learned: Humans are wimps. And, don’t expect your telemetry season will be cut short by sampling mortality.
Finally, and most importantly, brook trout are gorgeous creatures with complex and diverse ecologies. There remain so many unanswered questions.
Lesson learned: I picked the right career.
I have few field horror stories this week-probably because I was only out for one day. After sampling, we like to give fish a few days to calm down before tracking so that we aren’t documenting any movements that are from handling stress. My office to-do list has also been growing since May with deadlines now becoming more eminent and I think some no longer believe my “I’m in the field” excuse for not answering emails. So, I spent the majority of the week clearing my desk and staring at the data we’ve gotten so far.
We did go out once this week to track all fish locations. And, it was arguably the most interesting week for movement. As we started tracking one stream, we quickly noticed that a pool that normally contains five fish was down to one. It was irritating at first because we assumed they were lost to predation or post-handling stress mortality. But, as we walked upstream we started hearing the receiver “chirping” at odd locations indicating the location of a fish. They’re finally moving!
In total, several fish from one stream moved over half a mile with one fish approaching the one mile mark. A mile! That fish just moved >8000x it’s body length in a week.
What trigged the movements? It’s hard to tell because right now I don’t have a lot of movement data. But, a leading suspect is an increase in stream flow. A few days before we tracked there were several storms that dropped about four inches of rain. By the time we got out, stream flows had already gone back down to their near-drought conditions, but I think for a few days in there they increased just enough to trigger take off.
I’m always curious why fish decide to start moving after, in this case, two months of hunkering down. But, I’m probably more interested in why they decide to stop moving. Sometimes they stop in really bad habitat, and so maybe they just get tired or there is a resource (like food) there that I don’t immediately see. But, in this case, a more interesting first impression is that some fish seemingly made the decision to pass through some really great pools, swim up small falls, traverse through very shallow runs and find the exact same pool some other migrants chose to stop in. Did they know that habitat was there? Were they following each other? And, why is that pool better than all the others?
If fish could talk my job would be so much easier.
Fish Phlebotomy 101
he name of the game is the same: It’s hot, dry, and the fish are disappearing from predation. On Monday there was a panic when we showed up to track and there were several new tags gone. From here, the short-term plans I was brewing for the study went up in a gigantic ball of fire, and the lighter fuel looked something like this:
11:30am: A thunderstorm rolls through the area. I find spotty cell service to check the radar and I email my advisor a quick update (mostly to occupy my boredom). After an hour the storm clears, I’ve heard nothing from my advisor, so I carry on with my day none the wiser.
8:00 pm: I get back to the house after tracking and check email before going to bed. I find it odd that my email is taking a while to load, until I realize there are 67 new messages. I scroll down and see the names of my advisor and other collaborators popping up a few more times than they should. This can’t be good.
9:00 pm: After talking to my advisor, we decide to start sampling ASAP. This is why you don’t check email before bed.
1:00 am: Sampling crew contacted, weekend trip to Virginia pushed back, sampling supplies inventoried, mini panic attack that I just moved up a major aspect of my project by over a month.
So, why the sudden change? I’ve mentioned before that we take a gill and blood sample from every fish that we tag. One of the reasons we do this so that we can determine how fish are responding to temperature stress at a molecular level. In the spring we collected tissue from fish that were loving life at stream temperatures near 50°F. This is the equivalent to a relaxing spa day for us, and so it serves as a baseline for what tissues look like when fish are not stressed.
Fast forward and now trout are trapped in water that is 15° warmer and some of the molecular markers have changed in response to the heat stress. But, just like when you come inside to air conditioning after a hot day in the sun, as soon as the water cools down fish will return to baseline. Not knowing how long we have before the heat streak snaps, and because we have already lost so many tagged fish, we had to pull the trigger and push the sampling up.
We are still trying to decide exactly what we will look for in the tissue samples, but one focus right now is heat shock proteins, or HSPs. HSPs are produced by cells in response to heat stress to prevent cell death and are easily detected in the gills of fish. We know we should find a difference in HSPs from spring to summer to fall, but that’s not all that exciting (it will basically just tell us that HSPs are more prevalent when it’s hot).
But, more interestingly, we are curious whether some populations show an adaptation to chronic heat stress. While HSPs are necessary to prevent cell death, they are produced at the cost of reduced growth and reproduction. So, fish can’t just produce a bunch of HSPs because then they won’t have any energy to survive. We are curious whether populations that are exposed to more heat are more efficient producers of HSPs, are acclimated to heat and don’t produce as many HSPs, or if heat is stress that can’t be overcome.
We lucked out and accidently picked one site that is not only warmer than the others, but also more variable in temperature. So, we are curious to see how HSP production differs in that stream in comparison to the others. Regardless of the result, this is one of the first studies of HSPs in natural trout populations, so the results will help us forecast trout response to future warming or at least design follow-up studies to address the question.
For now, we have sampled a little less than half of the study sites. When we sample we are only targeting fish that are currently tagged, so in theory it should be easy. Wrong. These fish are incredible at finding little crevices to hide in, and despite knowing a tag is within 5 feet of you we are still averaging about 30 minutes or more per tag. The dilemma is deciding when to keep trying to recover the tag because you think it’s a hiding fish vs. when to give up because it’s a dropped tag in a deep hole. So, we’ve been throwing rocks, wanding heavy magnets to pick up tags, and pumping voltage (special thanks to Steve and Linda Szoke, who volunteered the first day and taught me a little patience in this task!). Slowly but surely, we’ll get there.
Loyalsock sampling resumes next week, but for now I’m in Virginia for a few days to catch up on non-field life and to help sample an urban stream I’ve been working on since 2006. Why do I volunteer to sample a tiny stream in July when it’s at least 100°F and the bulk of the work is counting juvenile minnows? You’ll have to stay hooked to find out….
How Low Can They Go?
It takes years to coordinate, design, and execute a telemetry study. When the wheels started spinning on this project I wasn’t even a graduate student at Penn State. So, needless to say, there is no way to plan around unpredictable things like weather. Coming off a relatively mild summer last year, all we could do was cross our fingers and hope that this summer would have the hot and dry conditions that are predicted to become more common in future years.
In this game of field work Russian roulette, we won. Loyalsock Creek is barely trickling. The pools that were once too deep to wade through barely touch my knees. Between Tuesday and Thursday we saw stream temperature rise as much as 7°F. The ground is now so dry that stream flows are still decreasing even after heavy overnight rains.
I’m not sure how much lower the streams can go, but we’ll soon find out. The forecast predicts even hotter and dryer weather for the next week. For the fish, this means several things. First, rising stream temperatures are going to create stressful conditions that put fish at a high risk of mortality. So, if you’re reading this and considering going fishing, it may be better to hold off until stream temperatures decrease a bit (which may be awhile). It’s a well-known fact that angling mortality dramatically increases at high temperatures because fish have a harder time recovering from hooking stress.
Second, fish are becoming sitting ducks for predators. With lower flows pools are shallower and many undercut banks and rock crevices that are good for hiding are no longer under water. Further, fish have a higher metabolism at higher temperatures. This means they are willing to put themselves in riskier situations and spend more time trying to forage at the risk of being nabbed by a bird or opossum. The last two weeks we’ve found many more tags in banks or dangling from trees. Unfortunately (but also interestingly) many of the predated fish have histories as being some of the more mobile fish in the study. This observation fits in with a lot of ecological theories of animal behavior, but it’s too soon to tell if we have enough data to definitively say that the “mover” fish are more prone to predation.
This past week we also surpassed 1000 detections, biopsy samples were delivered to the USGS Leetown Science Center in WV to start analysis, and plans are inching forward for August tagging. I continued to be overwhelmed by the support and interest that everyone has shown for this project. This week we started a conversation with a local news station about doing a segment about my project. So, stay tuned, literally, as The Troutlook may wind up on a television near you.
One last thing, on Tuesday I electrofished some trout to practice new suture techniques and accidentally caught a fish that was tagged in May. As you can see from the photos below, the fish was looking great with a completely healed incision and no infection from the antenna exit site.
What about friday?
Another week, another 200 detections. And, better yet, few dropped tags. We found three tags that seemed to be the victim of predation (most likely of the human variety this time), which was a huge relief after the struggles we had with dropped tags the last two weeks. Leaving Loyalsock Thursday night I was breathing a little easier thinking about the fate of this project.
But, wait…Thursday? What about Friday?
No, I haven’t forgotten that the work week is five days. But, by Thursday deep soreness sets into every major muscle group (who knew fingers could get sore?) and we are toting around a significant amount of data. I personally get a little nervous when a week’s worth of hard-earned data are stored on a single device that is prone to randomly turning off and gets temperamental when surrounded by too much nature (rain, for example, is an instant death sentence to the GPS).
So, it’s back to State College every Thursday night and Fridays are my day to play catch-up in the office. This “behind the scenes” work isn’t nearly as glamorous as the field. It starts well before sunrise (at least we have to wait until daylight to track!) with several hours of me pleading to the GPS to connect to the computer (I swear it plays games with me). Once I win that war, it takes a while to download the data, so I pass time repairing equipment, ordering supplies (August tagging begins soon!), and looking over the hundreds of emails I turned my eye away from during the week.
Sometime around mid-afternoon I finally circle back around to the data which appear as little non-descript dots on a map. Anti-climactic is an understatement. But adjust a few settings, work a little magic, look back through field notes, (make another pot of coffee), and suddenly there’s a twinge of excitement.
Like when you see that one 6-inch fish has moved over 7 football fields away. That may not seem like too far, but it’s over 4200x it’s body length.
Or you notice that some fish are moving between streams
And that there are some fish that consistently occupy habitats that are 2-3 degrees colder than other fish.
At that time you close the file, pack it in, and leave because if you look too closely you’ll spoil any chance of enjoying a little bit of the holiday weekend.
Happy and safe July 4th from The Troutlook! Don’t forget to look at the research tab for new information about the current project.