Ideas in this blog post are that of the author, and do not necessarily reflect those of other blog members or collaborating agencies.
I usually bite my tongue when I hear the phrase “wild trout.” In science, “wild” has a few different meanings. It can refer to a population that occurs in nature (as opposed to in a laboratory), or one that is, more or less, uninfluenced by human interaction. When we talk about trout, there’s generally little uncertainty that we are talking about a population that occurs outdoors. But, that later definition of “wild” can be a bit ambiguous. In reality, there are few truly wild populations of trout still present and so our use of the term has evolved with increasing human influence of fish populations. Is a heavily fished population wild? What about a population that was last stocked 50+ years ago? How about a completely remote population that has never been fished, but in an area that experiences acid rain? Science doesn’t have the answers to those questions.
But, what is more problematic than the ambiguity in the term “wild,” is that at some point it started being used in a way that made it difficult to distinguish from the term “native.” Likely because people wanted to distinguish between an actively stocked population, versus one that had established and was self-reproducing. I understand the desire to distinguish the two, but ultimately the choice of words has, to me, fueled one of the biggest challenges we have in native trout conservation.
Before I explain myself, let me define a few terms that are used to describe fish and wildlife populations:
Native: A species that naturally occurs in a particular location. That is, if we rewound the clock hundreds of years, this species would be there. On the east coast, brook trout are the only native trout species.
Nonnative: A species that does not naturally occur in a particular location, and historically would not be present. On the east coast, brown and rainbow trout are nonnative with the former being from Europe and the latter western North America.
Invasive: Definitions for this term vary, but the simplest is a nonnative species that causes harm to native populations. A nonnative species isn’t always invasive, and there is a lot of debate as to whether brown and rainbow trout are nonnative or invasive on the east coast (with the answer probably varying depending on the region).
Naturalized: A nonnative species that has existed in an area for long time (i.e., several generations) and is naturally reproducing.
Now, let me return to the phrase “wild trout.” Oddly enough, on the east coast it is rare to hear that phrase in reference to brook trout. It’s much more common for someone to say a “wild brown trout” or “wild rainbow trout” fishery. And, when they say it, they are generally trying to express to their audience that the population they are talking about is of high quality. But, should we reference large, nonnative trout populations as “wild?”
Before you answer that question, think about this. What if you replaced the term “wild” with “naturalized.” A naturalized brown trout fishery. That terminology conveys the same meaning but is less ambiguous and technically more accurate. However, I would guess that it doesn’t sit as easy with you and that, given the opportunity, you would value a “wild” fishery over a “naturalized” fishery. This makes sense- humans have a more instinctive connection to the word “wild”. We want to believe that what is wild is good and wonderful. “Naturalized” doesn’t evoke the same pleasant emotions as “wild.”
But, would you use the term “wild” to reference another nonnative species? A wild population of murder hornets. Or, a wild population of black rats? How about even a native species that is a nuisance? Wild poison ivy. Probably not, because you don’t want to associate those species with something pleasant and good.
The problem is that when we misuse the term “wild” in reference to trout, we run the risk of misinformation. If you are new to an area, or not quite up to speed on dynamics of all species in your local stream, then you might hear the phrase “wild” and assume a good, healthy, natural population. And, even if you later learn that that wild population is nonnative, it likely deemphasizes the significant negative effects that nonnative species can have on native populations.
I’m sure many readers of this blog already know that a “wild brown trout” is still nonnative. And, you may have read numerous times how brown trout often decrease the health and size of brook trout populations, and that studies have shown that nonnative trout do not fill the same ecological space as native trout populations, regardless of how morphologically similar. But, would your child? Your parents? What about your neighbor or the stranger you meet in the checkout line at the store? Probably not. Like it or not, anglers are environmental educators, and it is our responsibility to spread truth. Not opinion. Sometimes that means recognizing how something as simple as word choice influences the public perception of our natural resources.
Worse, using the term “wild” encourages you, and anyone you may speak to, to practice lazy stewardship. Ultimately, how we manage a fishery- including the species in it- comes down to what we value about that fishery. Should we value high population densities of large fish- regardless of whether the species is native or nonnative? Or should we sacrifice some fishing opportunity in order to maintain native-only populations? Does the answer vary by stream, or is it universal across an entire range?
It’s a difficult decision- but that’s just the point. It SHOULD be difficult. People should be given the opportunity to do the research, understand the costs and benefits to each scenario, and make informed decision about their own value system. But, intentional or unintentional, when we use “wild” to refer to nonnative species, we plant the seed that this species belongs here and that we should encourage future spread. If enough anglers are influenced by this terminology, wild trout will never win.
And, if you do decide that you enjoy that population of a nonnative species, what do you lose by using the term “naturalized?” Worse thing that could happen is that you spread valuable information.
Do you remember the scientific method from grade school? That discrete five(ish) step process that was engrained into your head as the way all great science is conducted. Make observations- develop hypotheses- form an experiment- collect data – generate conclusions.
Yea, it doesn’t always work that way.
Our recent manuscript on riverscape genetics (which you can download here) is a great example of just how messy science can be. I’d like to say that we started this project by announcing that we wanted to do a riverscape genetics study (I’ll explain that term in more detail below), or that we collected data with a very clear hypothesis in mind. But, those would both be lies. I started that project knowing nothing about basic genetic concepts, in a study system I had no intent to work in, and my only goal was to describe what I saw. Nonetheless, the result is a manuscript that I think (or, at least hope) makes a great contribution to science.
So, how did we get there? My PhD position came with no project funding or ideas, only a mutual interest between me and my advisor to study trout. Luckily, we quickly stumbled on a small grant opportunity, and we were pretty sure they would give us money if we 1) would work in the Loyalsock Creek watershed, and 2) study genetic diversity of brook trout. I was very happy to work on brook trout and being new to Pennsylvania I didn’t have any strong feelings about the location of research. But, genetics? I specifically avoided genetics courses in college and actively rolled my eyes at the research idea.
But, in the case of research, money does buy happiness and I needed research projects for my dissertation. So, the first project was set. We were going to describe how genetically related 20 populations of brook trout were throughout the watershed. No hypotheses, no experiments…just go out, collect data, and describe. And, honestly, I’m not sure how much difference the results would have made at the time. Brook trout populations often have low genetic diversity (which happens when fish don’t move between streams and populations become isolated from one another). But, how “bad” low genetic diversity is is debatable. Plus, solving it can be very difficult, not to mention expensive. Understanding population genetic diversity is good information to have, but rarely does it actually help change fish conservation and management.
It took about two weeks to sample fish from those 20 populations we initially agreed to study, but even less time to fall in love with Loyalsock Creek. So, after wrapping up the initial field work, I made plans to do a side project on fish behavior, and while doing it I decided to also collect genetic data at about 15 more sites. Those 15 extra sites were chosen with really little consideration for science, and the decision to collect genetic data at them was a leftover thought.
So, the summer flew past and I had samples from fish at 35 sites. “Samples” in this case refers to little clips from the caudal fin, which we can use to determine the genetic composition of each fish in that lab. That lab work takes a while, and I was about to leave to start research in West Virginia. But, before I left, I needed to provide a short update of our research and provide some preliminary results to the person funding the project. So, I determined the genetic composition of fish from a few sites and ran some basic analyses and found some surprising results. The trout had higher than expected genetic diversity, and didn’t seem to have clear patterns of isolation like we would expect if fish were not moving between streams. But, despite being interesting and unexpected, I was getting ready to start some new projects and didn’t have time to really think more about it.
At this point, I basically stopped working on the genetics project. I did about two more years of data collection in various other states and countries, eventually getting back to Loyalsock Creek to do a fish movement study. If you haven’t read about our telemetry study before, we tracked fish movement for eight months and found that basically no fish moved all summer. But, we found that about 20% of tagged fish have this interesting behavior where they seem to spawn in the small tributaries and then move into mainstem Loyalsock Creek. If you have never been to this area, don’t let the name “creek” fool you. Loyalsock Creek is actually a moderately sized river, and very atypical brook trout habitat.
Now things are getting interesting. My preliminary genetics data suggested that populations might be connected, and now I have telemetry data showing that some fish move to mainstem Loyalsock Creek. But, again, Loyalsock Creek is far from normal trout habitat, and it’s really not that many fish that seem to move. So, there’s two possible fates for fish that move to Loyalsock Creek. They could 1) just die, or 2) use Loyalsock Creek as a movement corridor to make effective migrations. Effective migrations refer to a very specific type of movement where an individual leaves one spot, moves to another, AND spawns there. We need those effective migrations to actually have populations connectivity and increased genetic diversity, otherwise movement does very little to population genetics.
So, how do we determine which of the two fates might be true? We conduct a riverscape genetics study. You can think of a riverscape as the aquatic version of a landscape- it’s comprised of all the habitat features that a fish might encounter as it moves throughout a watershed. In a riverscape genetics study, we determine which of those habitat features seems to be particularly important for increasing or decreasing genetic diversity. And, because genetic diversity is related to fish movement, it basically just tells us which habitats increase or decrease fish movement.
But, it turns out, there were no existing statistical methods that are specific to riverscape genetics, meaning we couldn’t really determine the effect of those habitat features on movement. Riverscape genetics studies have been conducted before, but they always borrowed methods from landscape genetics studies. Now, it’s quite obvious that water and land are very different thing. But, statistical methods in landscape genetics can’t fully capture the unique properties of rivers that influence fish movement.
To visualize this, think about a deer moving across land. That deer is basically free to move in any direction it wants. It probably moves most in forests, and might avoid roads (though, the amount of roadkill argues otherwise), but it technically can move in any direction. And, there’s nothing forcing it to move one more or less than the way or the other.
Now, think about a fish. Unlike that deer, it can only move where there is water. So, it’s forced to use the river network which, compared to land, is a very linear environment. The fish also has to fight against the flow of water, and so movement might be biased in either the upstream or downstream directions. So, to conduct a riverscape genetics study, we needed to use a statistical method that can account for the linear network and can handle the possible bias in movement in one direction (which we call bidirectional gene flow).
And, this is where we got very lucky. A member of my PhD committee was a statistician, who had been thinking of these exact ideas for a few years. So, we had data. He knew how to create the statistical model that would take care of the problems above. And, together, we created the bidirectional geneflow in riverscapes (BGR) model to account for the problems above. The BGR model is designed to be used in any riverine environment, and we tested it first on the data that we collected in Loyalsock help understand how fish were moving throughout the watershed. We used the model to see if a whole suite of habitat variables were important – anything from elevation to stream crossings to stream size. Ultimately, we found that four habitat variables seemed to influence fish movement Loyalsock most:
A useful part of this model is that, once we know which habitat features influence movement, we can create maps of relatively migration rates (relative here doesn’t mean number of fish, just that higher numbers mean higher migration). These maps can help highlight movement corridors throughout the watershed (like the mainstem), but also easily identify areas in the watershed where management and conservation might improve connectivity.
So, what does all of this mean? That “atypical” brook trout habitat might actually be some of the most important habitat there is for population connectivity. Mainstem Loyalsock is only inhabitable by brook trout for about half of the year, but during that time it is being used as a significant movement corridor to increase population connectivity. Anything that threatens habitat in the mainstem- be it climate change, reduced stream flow, water withdrawals, sedimentation, deforestation, barriers, etc- even at very small, local scales, could have very significant effects of brook trout populations across the entire watershed. It also means that conservation of brook trout habitat means more than just habitat enhancements to small streams.
More globally, if you’re conducting riverscape genetics studies of any species, check out our BGR model. It’s easy to run (even if the manuscript doesn’t make it sound like it is) and provides more informative results than other methods that you may be thinking about. The results we provide here are likely to change depending on where you are working and the behavior of the fish you are studying.
And, what I find funny about all of this is that we probably wouldn’t have discovered these patterns had I not randomly gone out to study 15 extra sites that first summer of data collection. It turned out that some of those sites had the highest genetic connectivity, which is what initially tipped us off that fish might be using the mainstem as a movement corridor. So, if I had to revise the scientific method for this project, it would look more like collect data- forget about results for three years- get lucky- communicate findings. And, honestly, I think that’s probably the more likely sequence of events for most scientific professionals.
After determining which habitat features influence trout movement, we can create these maps of relative migration rates in the downstream (top) and upstream (bottom) directions. Zooming in, you can see the effects of barriers (circles) and temporarily dry stream segments (squares) on migration rates. These maps can be used to easily visualize where conservation efforts could be focused to increase movement.
We’re all guilty. Maybe you’ve just caught a huge fish, are fishing a new spot and catching a cool new species, or perhaps your son or daughter just caught the first fish of their life. Regardless the occasion, what’s one of the first things a lot of us do? We reach into our wader pockets and grab our phones to document the occasion with a few well-staged photos and share them to Facebook, Twitter, etc.
It seems innocent enough. Afterall, you probably used the best barbless tackle, took all the proper handling precautions, and snapped the photo as fast as possible. And, you watched as the fish swam off. No harm done, right?
Actually, you might be surprised to learn that a recent study found that up to a 1/3 of all fish photographed by anglers died within the next day.
I personally found that number a little startling but, let’s take a deep breath before we jump to conclusions. We have to recognize that the mortality rate is obviously going to depend a lot on angling method, photography method, time of year, etc. So, let me set the stage a little. The researchers were targeting a lake-dwelling population of bull trout, where water temperatures were about 56°F. So, not overly warm, and surely not as thermally stressful as a lot of trout streams we fish in summer. Tackle included barbless hooks, and fish were landed as soon as possible. In other words, the angling conditions were basically ideal.
On one day all fish that were caught and were of “memorable” size were photographed twice, measured for length, and then photographed twice again (more on what I mean by “memorable” below). This behavior sounds a bit bizarre, but other studies have shown it’s typical angler behavior after catching a big fish- they call their buddy over to snap a photo, measure the fish’s length, and then usually take photos of the fish being held by their fishing partner. All in all, the time from the fish being caught to released was less than two minutes. Two minutes sounds like a long time but, again, studies have shown that it’s generally about the length of time most people hold a fish before its released, and I guarantee you the clock ticks a little faster with your adrenaline rushing. And, if you really want to argue, other studies have shown negative effects of air exposure after only 10 seconds. Good luck fumbling to get your $800 phone in the middle of the stream in less than 10 seconds.
So, that was day one. On day two the researchers did the same procedure. Only this time any memorable-sized fish were immediately released. Importantly, in both instances fish were released into a holding pen. Then, 24 hours later, the number of dead fish in each pen was counted.
The result? In the group of photographed fish 10 of 30 (33%) died. In the fish that were immediately released, 3 of 20 (15%) died. What this tells us is that, even for the most experienced anglers working in some of the best fishing conditions, there is mortality associated with catch-and-release fishing. This is important because we assume that catch-and-release protects a fishery, and it does to a large extent. But, there is a category of mortality, known as cryptic mortality, that is difficult to account for and includes things like death from injury, illegal harvest, and prolonged handling. While mortality from harvest and injury is near 100%, it’s not a common outcome for most fish. However, many fish experience prolonged air exposure and, though mortality from air exposure is not 100%, it adds up to eventually account for a significant proportion of deaths in a fishery. And, access to more portable cameras (i.e., smartphones) and increased social medial influence may increase the likelihood that fish are exposed to air for longer durations.
Of course, we have to consider these numbers with a bit of caution. Fish weren’t released back into the lake, but rather into confined pens. This could have increased stress, and thus artificially increased mortality rates. But, the researchers noted that most deaths occurred almost immediately upon release. And, the pens had pretty nice accommodations. If anything the physiological responses to prolonged air exposure (reduced swimming ability, increased thermal stress, etc.) may actually have less effect for fish that are released into a protective pen, in which case the study may underestimate mortality associated with photography. In fact, after the study was over, the researchers released the fish back into the lake and found that two fish that were technically alive sat next to the pen for over four hours, appearing to be weak and near death. So, arguably, you could say that 40% of photographed fish died during this study.
Another important point is that this study was conducted on a fairly remote lake, and so the fish had only been caught the one time. In reality, fish that survive one landing are likely to be repetitively caught in a catch-and-release fishery. Every time that fish is caught and handled there, the probability of it later dying is going to increase. And, potentially, the effect of previous handling could make a fish more susceptible to prolonged air exposure in a later catch.
Now, I want to return to the fact that this study also focused only on memorable-sized fish. In fisheries science, “memorable” is a technical definition that means exactly what you would think- a fish that is large enough to be remembered. But, for the purposes of this study, memorable also means a fish that is larger than you would normally catch, and so the chances of dropping the fish or awkwardly handling it are higher. Subsequent review of the photographs showed that most fish were covered in mud, indicating they were either dropped in the process of taking the photo or there was increased struggle trying to land the fish. The focus on large fish may seem a bit biased but, think about it, do you bother taking a photo of many of the smaller fish you catch? Probably not. Plus, understanding delayed mortality of larger fish is potentially more important as the larger fish are likely those that will produce the most offspring, may have different movement behavior than smaller individuals, or may have unique genetic diversity.
So, how do we possibly prevent photograph-induced mortality. Some states, such as Washington, have made it illegal to totally remove some species from the water if you are going to release it back into the stream/lake. So, basically, the only way to take a photograph with a salmon, steelhead, or bull trout in Washington is if you are also taking it home to fry. Is this a reasonable practice? Maybe, but it’s difficult to enforce. Ultimately the best way to decrease mortality from prolonged air exposure is by influencing individual angler conduct. In other words, we need to self-enforce best angling practices that minimize fish air exposure. This is particularly critical in summer, and in streams/rivers with flow, as these conditions are going to maximize post-release mortality.
So, maybe think twice before you click the “Like” button on a picture of your friend standing on a boat or streamside with their prized catch.
This post was inspired by recent research published by Brian Joubert and colleagues. I would encourage all to read the original manuscript found here.
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.
I recently read a post on the Eco-Evo Evo-Eco blog by Steven Cooke on how a prolific ecologist can achieve work-life balance. Steven offers great advice, some of which I’ll echo below. However, his guidance comes from the perspective of a successful professor managing a very productive lab, not that of a graduate student who’s constantly staving away impostor syndrome while living away from family and friends and questioning their career/life choices (not to say ‘adult’ scientists don’t do this too, but these are hallmarks of graduate studies). The mindsets, time commitments, and confidence levels are very different at those two stages of one’s career. So, I responded to a Twitter post by one of the blog’s moderators, Andrew Hendry, suggesting that it would be interesting to hear the perspective of a graduate student. So, here we are…
Before I start, a little background for those who don’t usually read this blog. I’m a few months from finishing my Ph.D. at Penn State, where I’ve spent the last few years studying behavior and adaptive capacity of coldwater fish. I’m not sure graduate students can be described as ‘prolific’, but my peers frequently use words like insane or intense to describe my productivity, perhaps suggesting unrealistic levels of commitment to my research (okay, maybe not ‘perhaps’). In some respects, they aren’t wrong. As a graduate student, I recognize I am still trying to figure out the best way for me to achieve work-life balance because, as Steven suggests, there’s no secret recipe for success. Everyone has to figure out what works best for them. But, I’ve made a few realizations over the years that have made it easier to balance the scale.
My biggest realization was learning that the reward for working more now was simply more work later. As a graduate student (and anyone in academia) there will literally never be a time when I couldn’t be working on something. It might be something tangible, like a manuscript draft or a presentation deadline. Or, it could be that folder of journal articles on my computer that I “should” be reading (and that never seems to quit growing). But, if I do that work today, then it just clears my schedule to do a different task tomorrow. It would literally. never. end. Learning to accept that my to-do list will never be cleared was a big challenge- so big that to break the cycle I had to start leaving my laptop at the office a few days a week. What I quickly realized was that there was no email, analysis, or manuscript that couldn’t wait until morning. I also realized that with my newfound freedom came the ability to enjoy my home life and hobbies without nearly as much guilt and doubt about how I should be spending my time.
But, this only works when my to-do list is manageable and I stay a little ahead. If I overcommit, slack off, or schedule meetings poorly, then I usually do have to bring my work home with me to keep putting out the fires. A couple weeks of this and it does feel like I’m managing an inferno. I’ve learned to minimize these times by simply saying ‘no.’ No to some seminars, working groups, classes, meetings, and yes, I even say no to happy hours. In a large university it is easy to spread yourself too thin by trying to attend everything. But, the return on investment for many of those events simply isn’t worth it. At first I felt guilty for dropping some things off my schedule, but it quickly wore off.
It also just made sense to set boundaries on evening commitments. I choose to get to the office everyday by 5am. I am a morning person, but I also have a tendency to get distracted by discussions with friends or collaborators in the hall and by my undergraduate advisees. I love these interactions, but they can derail my entire day. However, by the time the hallways start getting busy, I usually have a good four hours of productive, undisturbed work that’s much easier to return to when I do start chatting. Now, do I leave by 1pm feeling proud of a full 8-hour work day? Sometimes. And sometimes I stay until 6pm (I told you I’m working on it…). Regardless, I found a time of day, location, and schedule that works for me. And, I respect that schedule as if it came from my boss. It’s a double-edged sword that no one is forcing me to be anywhere at any time to complete my workday, and I find that if I don’t hold myself to some regular schedule my productivity declines.
If you're going to have work "win," I would suggest exploring some incredible places of the world to work in.
Now, here’s where I really think there is some departure between the work-life balance of a professor and a graduate student. I’m not managing a lab, which comes with its own stressors, expectations, and deadlines that I can’t speak to. But, I am often collecting all of my own data, running analyses, and trying to learn a completely new skill. This takes a lot of time on top of my regular commitments. Sometimes a lot of consecutive time spent away from home on nights and weekends. I basically spent my first two years at Penn State working 80-hours a week in the field in a different country, a different state, or deep in the mountains of Pennsylvania. Work won. But, importantly, not only was I okay with that, but I knew when I started at Penn State I would likely be doing that. Not everyone will be in a position to live away from their family for days to months at a time, and that’s okay. But, whether they admit it or not, almost every advisor will expect you to sacrifice your home life to some degree. It could involve long periods of time spent away from home, or just simply putting a little extra time in when you have a tight deadline. Communicate with your advisor, ideally before accepting a position, what your home life can afford. If they don’t respect that, then you probably don’t want to work with that advisor anyway.
Now, there’s really no way to avoid long periods of time in the field. But, what I realized is that I was somehow treating office work in the same light- that it simply wasn’t possible to finish a task unless I was working very long, uninterrupted, hours on it. It was very productive, but every time I undertook a new project I found I was generally unhappy. The time management skills I discussed above helped, but I was also dissatisfied that when I enforced some resemblance of work-life balance I stopped feeling productive. So, I had a decision to make- either put in more time or get better at using my time. Forcing myself to choose the later has resulted in a huge change in my happiness and productivity. As the saying goes, ‘work smarter, not harder.’
For example, writing. I enjoy writing, but found the time involved was simply not sustainable. After a little self-reflection, I identified the time bottleneck in my process- I was treating Microsoft Word like a stone tablet. I was agonizing over every word that I would get nowhere for days, sometimes weeks. Finally it hit me. Just type. I can get an entire manuscript draft in an hour. It’s absolutely terrible, at times nonsensical. But, after one hour I’m no longer staring at a blank page. And, instead of writing a manuscript, I’m editing a draft. It’s a subtle difference, but editing can happen in much shorter, discrete time intervals than writing, which was important for me given my propensity for distraction. Do I claim this writing style can work for everyone? Absolutely not. But, finding ways to be more productive in the tasks that notoriously take the longest has made me a better graduate student, but also a more productive, respected collaborator.
Another time saver was that I stopped aiming for perfection. A manuscript draft at 90% is going to get perceived by my coauthors the same way as a manuscript draft I feel is 100% final. That last 10% has far more to do with my personal preference on writing style, which I’m in a better position to fix after I’ve divorced myself from the manuscript for a bit. I also got really comfortable with admitting my own stupidity. I’m surrounded by brilliant scientists who are all skilled in very diverse aspects of ecology. I love being a self-learner, but at some point it’s insanely faster to phone a friend than it is for me to continue beating my head against the wall.
I’ve also learned to give up. I’ve spent entire days in the office doing nothing but trolling YouTube, talking to my friends, and occasionally going to the bar at 11am. Sometimes I’m just not feeling what I’m working on, and it’s not worth the mental energy to force it. On a good day I can refocus my energy to another task, but I’ve accepted that sometimes that ‘task’ is to just take a break. Nothing productive is going to get achieved if I’m burnt out. And, productivity that sacrifices happiness isn’t a long-term recipe for success. So, I minimize burn out where possibly by protecting time for sleep, exercise, good food, and good friends, and just give in to it when I see the fuse starting to burn. And importantly, I just don’t care about the competitive arena that feeds into graduate school. I don’t care if someone worked longer hours, published more papers, or got more awards. My advisor hasn’t (yet) complained about my status, and my version of work-life keeps me happy. That’s enough.
Finally, I’d like to echo Steven’s post and talk about what I feel like I’ve sacrificed to achieve everything I have. The short story is not much. But, I think this is only possible if you truly love what you do every day. It sounds cheesy, but I am very fortunate to have figured out very quickly exactly the research questions that I am passionate about, and I love pursuing them (most days) under the guidance of an incredible advisor. I unapologetically take a lot of time off during the holidays, though summer field seasons have left very little room for family vacation. I think the biggest sacrifice I have made is essentially putting my life on hold while getting two graduate degrees. There are definitely times I would love to be settled in a permanent city with a permanent job and be adding to my retirement account. The reality is that I have no idea where I’ll be living in a couple months as I search for a postdoc, nor where I’ll be 1-2 years after that.
This one goes out to all my readers down south.
Northeast brook trout populations are what I would call “typical.” Fish move around some, but not a lot. Populations are not too genetically diverse, but there’s enough there for evolution to work with. No one stream contains a ton of fish, but we aren’t typically concerned that a population could be extirpated next year.
Drive a few hundred miles south and we’re telling a different story. There, brook trout populations are living life on the edge- literally and metaphorically. Southern-edge populations often live in streams that are hot, lack abundant food sources, and are threatened by barriers and an abundance of nonnative species. Compared with populations in the northeast, southern populations are also must older because they were never frozen out by the glaciers. But, with age comes genetic wear and tear- the older a population gets the more likely it is to have lost some genetic diversity due to random chance and catastrophic events that cause large population declines (floods, disease, etc.). Put all this together- the lack of connectivity, the low population sizes, and the limited genetic diversity- and southern-edge brook trout seem destined for population collapse.
When populations get isolated, and when genetic diversity starts to drop, biologists often start questioning whether we should intervene. It wouldn’t be hard- we can simply do what brook trout used to be able to do themselves and move individuals between populations. We call this physical movement of individuals among populations translocating. With a little luck and a lot of research and planning, the translocated fish will spawn with the resident fish, and their offspring will have increased genetic diversity that contributes to the population for many generations after. This is exactly what we want because, as genetic diversity increases, we often see an increase in number and size of individuals in a population. Perhaps more importantly, we also see that genetically diverse populations are better able to survive disturbance events. Translocations must be a no brainer, right?
But, here’s the catch. The populations down south have been isolated for so long that many of them have evolved their own identity, and potentially might be on their own evolutionary trajectory. Translocations are only successful if the fish moving into a population have genetics that are similar to the resident population. Otherwise, the offspring may be genetically more diverse, but those genes may make fish poorly adapted for life in that environment. This is tough, because it can take many generations to realize that the translocated fish are having a negative effect, and by then it could be impossible to turn back the clock.
The genetic risks associated with translocations have been known for a long time. But, the south brings up another, more philosophical, dilemma. If we start translocating fish across multiple watersheds, we potentially erase all of those genetically unique populations. Do we really want to do that?
Seriously. That is my question to you. What is more important? A genetically distinct population that could collapse within the next 50 years? Or, a population that loses some of its uniqueness, but perhaps has more long-term stability?
Here’s the fun part- scientist haven’t decided the right answer. On the one hand, you have to balance the risks of translocation with the potential for population collapse due to low genetic diversity and isolation. But, who’s to say that the isolated, distinct population wouldn’t survive just fine on their own? Populations above waterfalls have existed for hundreds of years and they are doing just fine. On the other hand, what is the value of these genetically distinct populations? Are they locally adapted to those streams, and therefor possess unique genes that are worth conserving? Or, are they just one in the same with the neighboring populations?
We’ve definitely got some important decisions to make, and the right answer will surely vary across watersheds. But, perhaps the decision doesn’t need to be so black and white, either. For example, we probably don’t want to move fish with strong hatchery influence to watersheds that are comprised of completely wild genetics. This is particularly true given that fish stocked in the southeast are often descendent of the northeast (turns out…southeastern brook trout are hard to reproduce in captivity). But, what if we look at the watershed as a whole, identify the populations that have completely wild genetics, and only translocate to/from wild-only populations that are somewhat similar? Maybe this is a good compromise that would lead to moderate increases in genetic diversity while still maintaining some unique genes in the population.
Now is the time to be having these discussions. I recently sat down with the Trout Unlimited Southeastern Volunteer Coordinator and we chatted about how some states have very restrictive translocation policies making it difficult to do reintroductions or translocations. Good for those states, because they are probably also limiting the spread of hatchery genes into wild populations. There are still so many uncertainties that I think conservative approaches are probably the best choice right now for most streams. After all, most brook trout populations will be fine for the next few years while we take the time to do our due diligence and research needed to make the right decision.
But, pretty soon we do need to start having these discussions. Will you be ready to contribute?
This post was inspired by recent research published by Kasey Pregler and colleagues. I would encourage all to read the original manuscript found here.
There’s nothing like field work. Breathing in the fresh mountain air while hiking to a remote population of native trout. Watching the sunset over a stream after a long day’s work. And, getting back to the office sore and full of new research questions after seeing nature at play.
Unfortunately, not every research question I think of in the field, can actually be studied in the field. Nature if far too unpredictable and uncontrollable, and fish far too smart, for scientists to risk putting lots of equipment, time, and money into a field-based study. At least not without some careful pilot studies, often conducted in a laboratory. Before coming to Penn State, I used to dream of having a little indoor stream I could use to test some ideas I picked up along the way about fish behavior. Nothing too fancy- just a couple pools and riffles, and a nice population of brook trout. The possibilities would be endless.
Dreams came true within weeks of starting my Ph.D. and finding out that Than Hitt of the USGS Leetown Science Center in West Virginia had…you guessed it…an indoor stream. Complete with..you guessed it again…pools, riffles, and brook trout. We got to work quickly, setting our eyes on understanding how brook trout use thermal refugia- small areas of groundwater upwelling that, in the summer, have water temperatures that can be much lower than average stream temperature. When we started the research, we knew that studies had shown that trout that occupy areas of thermal refugia may be able to survive periods of thermal stress, which could mean that there might be some hope for trout populations facing future stream temperature rise.
But, observing how fish use a thermal refuge in the field had historically proven to be difficult and mostly led to a lot of confusion. For example, previous observations had shown that fish move really far to access a thermal refuge, but then frequently end up leaving the refuge shortly after. This made no sense. If the stream is too hot for the fish, and the thermal refuge is the perfect temperature for the fish, then shouldn’t the fish….you know…stay in the refuge? Welcome to science.
So, why? Why are fish leaving what seems like their own climate-controlled rooms for what surely seems like a death wish? We had two main thoughts. It could be because competition inside the refuge was so high, that fish that couldn’t hold their own got pushed out. Seems plausible, as brook trout are extremely territorial and aggressive. The second thought was maybe the refuge didn’t have other important resources. It might have thermal habitat, but maybe it doesn’t have food, cover, and good flow. So, fish might occupy the refuge for a while, but eventually they will have to leave to fulfill other requirements.
This is where the stream lab proved to be perfect. We could easily manipulate temperatures (thanks to the incredible team of USGS technicians and biologists at Leetown), monitor individual behavior, create some separation between thermal and forage habitats, and start teasing apart why fish were leaving their cushy thermal refugia. Frequent readers of this blog may have some déjà vu and realize that this isn’t the first time this study has been mentioned, as it’s been a topic that Ben Kline, the lab’s undergraduate research assistant, has been writing about for the last year. After we collected all the data in Leetown, Ben did some heavy lifting to analyze videos of fish aggression and millions of lines of data that documented fish resource use. And, I’m happy to say the data are finally in, and I’m confident to share some conclusions. Like….
Big fish really hate hot water. When stream temperatures were cool, big fish ruled the roost. Again, not surprising because brook trout are aggressive, and big fish are typically the most dominant. But, as stream temperatures increased, big fish stopped defending territories near a feeder in the warm part of the stream and spent most of their time in the thermal refuge. Surprisingly, once in the refuge, they basically stopped fighting. Huh. Now, it’s important to point out that fish don’t do anything “to be nice” to their neighbors. They are mostly selfish pricks. They didn’t stop fighting to let other fish into the refuge, but they probably stopped fighting because they didn’t have the energy to fight. The warm water was really sucking the life out of them.
So, the idea about competition influencing fish movement? Wrong. Fish were choosing to leave the refuge.
So, let’s consider the resource hypothesis. In our stream lab, the only area that fish could feed was outside of the thermal refuge. What we found was that, yes, fish did spend most of the time in the thermal refuge when stream temperatures were hot. But, all fish did occasionally make forays into hot water to feed. So, it would appear that our hypothesis about fish leaving the refuge in search of resources may hold some weight. It’s also interesting to note that smaller fish tended to leave the refuge more often, as well as stay outside of the refuge for longer, than bigger fish. So, this is another line of evidence to suggest that warm temperatures affected bigger fish more.
Why do these results matter? Well, we typically assume that the presence of thermal refugia alone is good enough to increase population survival when stream temperatures rise. However, what our results may suggest is that the location of refugia relative to other resources in the stream may also be important. If a stream is too fragmented, then fish will need to spend too much time outside of the refuge in search of resources, and so the presence of refugia may do little to conserve fish populations. Alternatively, if resources are nearby, fish can likely make quick trips back and forth among habitat patches, equivalently “charging their batteries” in the refuge before going in search of food. But, also keep in mind, smaller fish may be the most successful at making these jaunts into warm water, so fish size may also be influenced by refuge habitats.
Another important finding is that small refugia may have large benefits to populations. Because of reduced competition in the refuge, and the constant movement of fish in and out, a lot of fish may be able to take advantage of the thermal properties of refugia. So, the population-level benefits of a single refuge habitat may be larger than we currently believe.
Now, to take it to the field…..
I’m hopeful that if I asked readers of this blog to make a list of conservation priorities for brook trout, increasing connectivity would make everyone’s top five. It seems I circle back around to connectivity in most posts, with discussions of how movement of individuals among streams increases population resiliency, adaptive potential, and overall population health. Last week I even posted about how we should prioritize culvert replacement to increase population connectivity.
So, I’m here now to say…..maybe we should build some dams.
No, I haven’t changed my mind on the benefits of population connectivity. And, no, I haven’t lost my mind (at least not in this regard). Movement barriers may be a saving grace for some brook trout populations.
How? Well, if brook trout can’t move, then neither can our favorite foes, the nonnative trout. Neither can most other species that may be moving into small headwaters to find cooler waters during summer, such as creek chubs, pan fish, and bass. It’s essentially like clicking pause on the species composition upstream of a barrier. Kind of cool, uh?
The idea isn’t a terribly new concept. Out west, they’ve been installing barriers for a while to prevent nonnative brook trout from accessing native cutthroat trout populations, as brook trout cause rapid declines in cutthroat trout populations. When bait bucket biologists don’t interfere, installing barriers can be an extremely successful management practice that prevents nonnative fish invasions, but also stops the spread of invasive macroinvertebrates, diseases, and hatchery fish.
But, connectivity is still key to fish population health. So, it comes down to determining which is the lesser of two evils- nonnative species invasion or population isolation. As you can probably imagine, there is no single solution for every stream. But, before we can even start discussing whether purposeful isolation is a viable management strategy, we need to answer two main questions. First, does isolation actually achieve the intended results; namely a stream composed of only brook trout and other native fish? If it doesn’t, then we are just wasting our time and money by installing barriers, and potentially doing a lot of harm by restricting movement. Second, is isolation just delaying the inevitable and eventually cause populations to collapse from inbreeding and environmental disturbance. If so, again, we may just be wasting our time and money.
Unfortunately, we don’t have a great feel for the long-term repercussions of purposeful isolation. All ecological theories would predict that an isolated population should eventually become extirpated through the effects of inbreeding, random loss of important genes in the population, and the inability for recolonization following a disturbance event that wipes out an entire population (which, as we’ve learned in rainy Pennsylvania the last few years, is a common phenomena in small trout streams). Nonetheless, for reasons really talented scientists don’t entirely understand, brook trout seem incredibly resilient to isolation. We are all well aware of thriving brook trout populations above waterfalls that seem to be completely fine despite hundreds of years of isolation. So, even if purposeful isolation only buys us a couple hundred years, I think most people would agree it’s worth the investment.
But, it is fairly easy to address the first question, which is exactly what researchers from Allegheny College recently did in a new publication. After assessing the species composition of 78 brook trout streams in Pennsylvania, they determined that brook trout-only streams were significantly more likely to occur above barriers, and that over 90% of streams with brown trout had no barrier present. This isn’t terribly shocking (again, barriers block fish). But, fish get into odd places all the time. This is especially true for species that are as beloved as trout, and for which there is no end in the number of people willing to invest their own time and money in moving them around watersheds to ensure their own angling opportunities. Sadly, it happens all the time.
So, with evidence that barriers do seem to be successful at blocking nonnative fish invasions, the weight might be shifting in favor or installing barriers. But, just keep repeating to yourself: ‘connectivity over isolation, connectivity over isolation…..’. Always prioritize connectivity where possible. Maybe not all streams are equally as vulnerable to invasion, and so maybe don’t need a barrier.
The research crew from Allegheny College also looked to determine which streams may be particularly vulnerable to trout invasion. Their findings suggested that brown trout have the highest invasion potential in streams that obviously don’t have barriers, but also streams that are larger, with lower slopes and a few degrees warmer. So, in short, brown trout are most likely to invade streams that are a little lower in the watershed and, thus, those sites might be the most reasonable locations to consider barrier installation.
Though not discussed in the research study, it’s also possible that barriers could be particularly beneficial if trying to remove nonnative species from a stream reach. Once a species invades and establishes, it is difficult, if not impossible, to remove them from a system because there will likely be a constant influx of individuals from elsewhere in the watershed. But, if a barrier is installed, and then there is a couple years of manual removal, then it might restore a stream back to native-only.
But, remember….connectivity over isolation, connectivity over isolation. We still don’t have a great handle for the long-term consequences of artificial isolation. Until then, we can think of this as another useful tool in the management toolbox. But, think of it like a highly specialized, expensive tool that we should only use for very special occasions.
*Note: Content in this post is my own and may not reflect the opinion of the manuscripts' authors or the agencies they represent. I encourage you to read the manuscript, found here, so you can contribute to the discussion.
We all know one. An ugly, impractical beast that you just can’t imagine was purposefully constructed. At the same time, you know Mother Nature would never do one of her streams that dirty.
That’s right, today we’re talking culverts. The pipes, concrete boxes, and rebar that tunnel streams under roadways and railroads. The idea behind a culvert is simple: it needs to be strong enough to support the road above ground, and big enough to pass the water below ground. But, turns out, after 150 years in the business, humans are still trying to figure out the right balance between the two.
Some of the earliest design criteria for a culvert were published in 1853 in the 6th Edition of A Manual of the Principles and Practices of Roadmaking. Simply put, they recommended that culvert “size must be proportional to the greatest quantity of water which can ever be required to pass, and should be large enough to admit a boy to enter to clean them out.”
Really, we’re using “boy” as the unit of measure?
Today we might scoff at the inadequacy of those basic requirements for culvert design. But, for 1853, that simple recommendation was revolutionary. It also spurred rapid advancement of basic hydrologic theory because, at the time, there was no way to measure the “greatest quantity of water” that would pass through a culvert. We could guess, but flows are tricky- there’s drought and wet years, hurricanes, and heavy snows. So, some brilliant mathematicians worked out the numbers, and by the 1900s they found fairly simple equations that could estimate flood recurrence intervals and peak discharge. Crazy enough, these equations were so good that they still form the foundation of those calculations today.
But, something was still missing. We might know how much water passes past a point (otherwise known as stream discharge), but what’s the most efficient structure for facilitating that stream flow? It wasn’t really until the 1920-1950s where scientists started considering the position of the culvert in the stream. Should the culvert be completely submerged? Mostly out of water? What if the inlet is completely submerged, but the outlet not? Vice versa? Things get complicated fast. And, while we’re now better at designing culverts, we still aren’t 100% sure the answer to some of those questions.
Complicating matters is that oftentimes the most efficient way to transport water isn’t the most fish-friendly design. It turns out, fish are really finicky when it comes to culverts. They like a very set amount of flow, substrate sizes, and shade. If the culvert is too long they won’t pass completely through. If the water depth on either side is too deep or shallow, they won’t pass. Some species are more divas than others, but all have a very narrow window of conditions they are willing to tolerate.
Do you know how scientists found out that fish weren’t passing through culverts? The hard way. After decades of data collected on millions of culverts and hundreds of studies on fish swimming and jumping abilities, we have refined our understanding of what makes a culvert “passable” or not by fish. Unfortunately, when we started looking at culverts with a critical eye, we started realizing that many need to be replaced in order to achieve adequate fish passage. Replacing a culvert is no easy feat. It’s expensive, requires a lot of work hours, can be a huge hassle with traffic, and could also endanger fish populations in the stream. Making matters worse, a lot of culverts that need replacing aren’t even that old. The really poorly designed culverts- the ones that dangle feet off the stream bed, or are crumpling- may be a few decades old. But, many culverts that score low on the fish passage test are less than 10 years old. Before we start tearing down was is essentially brand new infrastructure, we better be sure that the end result will be restored fish passage, increased population connectivity, and overall increase to stream health.
That was part of the motivation behind a study that researchers from West Virginia University recently undertook. Simply put, they sought to determine whether culvert restoration will restore brook trout connectivity. Using genetics, they found that before culvert replacement populations below and above two culverts in West Virginia were structurally dissimilar. Otherwise, very few, if any, brook trout were swimming through the culvert and the populations above the culvert were genetically isolated (to read more on why genetic isolation can spell bad things for brook trout populations, click here). After culvert replacement, they found immediate evidence that fish were swimming upstream and that population connectivity had been restored. Success!
But, let’s not go tearing out all the culverts just yet. This was an obvious case where skilled engineers and biologists worked together and installed a culvert that was designed better than the one that was previously in place. But, sometimes it’s not that easy. Sometimes, what should be a great culvert still doesn’t result in great fish passage. And, a culvert that doesn’t seem so great by design is biologically functioning just fine. Biology is oftentimes more than a numbers game, and it’s worth reiterating that there’s no one solution to every problem. That’s what is making the science of culvert design frustrating and at times slow. There’s so many variables, and nature can be so unpredictable.
Further, even if we did know the perfect culvert design for every stream, there is also the question of whether populations really should be reconnected. If the isolated population has great genetic diversity, large size, and is seemingly healthy, then maybe it’s okay to place that stream low on the priority list for culvert replacement. Or, if downstream of an impassable culvert there is a thriving population of a nonnative species, maybe we should start considering whether we want to purposefully prevent fish passage.
That’s right, I said it. Go against everything I, and science, have ever told you and PURPOSEFULLY keep populations isolated. But, that’s a story for the next blog…
*Note: Content in this post is my own and may not reflect the opinion of the manuscripts' authors or the agencies they represent. I encourage you to read the manuscript, found here, so you can contribute to the discussion.
That’s one of those fancy words scientist love to throw around to make our sentences more sophisticated. And, for some reason, journals are more likely to publish “freshwater ecosystems are among the most imperiled worldwide”’ than “kiss ‘em goodbye, freshwater streams are tanking.” Beats me.
But, think about that (using whichever sentence you prefer). Freshwater streams are among the most threatened ecosystems on this planet and, on average, freshwater fish are going extinct far faster than marine animals and all the air breathers. That’s no joke. We hype up the polar bears (for good reason….), while in plain sight is an ecosystem that is crashing before us. To put this into perspective, if we consider local extinctions, otherwise known as population extirpation, from climate change alone, the frequency of local extinctions in freshwater ecosystems is about 20% higher than marine or terrestrial environments.
But, let’s play devil’s advocate. A local extinction simply means a species is lost from a specific ecosystem. For example, brook trout might go extinct from a specific stream reach. When a species goes missing, it leaves a hole in the ecosystem that usually gets filled by another species that, in many ways, operates in the same way. The new species will usually eat the same stuff, have the same population sizes, and seem to be a 1:1 replacement. But, is it really the same?
Think about it from a business perspective. If all the burger restaurants leave town, it opens up the market for another burger restaurant to move in. But, not all burgers are the same. Will the new place have the same menu? Will the food taste as good? Will they generate as many jobs as the old?
Will new species function just like their locally extinct predecessors? A study recently found that the answer is probably not. And, a species doesn’t necessarily have to go extinct for the ecosystem to fundamentally change after a new fish species move into down. Invasion fundamentally changes how an ecosystem operates.
Looking across continents, a group of researchers aimed to answer the question “how much does functional diversity change when a species invades a freshwater ecosystem.” You can think of functional diversity as the “menu” of the new burger restaurant. It’s basically how a species operates within an ecosystem- how far does it move, how much does it reproduce, what does it eat, how does it interact with other species, etc. Big changes in functional diversity can mean big changes to other fish species present in a stream, as well as the insect community, plant community, and the flow of nutrients through the environment.
What the study found was that species invasions increased average functional diversity by 150%. If you want to continue with the burger analogy- the menu of the new place is 150% larger. But, bigger is not always better. A pristine ecosystem evolved with a certain amount of functional diversity, and an increase by 150% means that the ecosystem is probably getting stressed in new ways. For example, they found a general pattern that invading species having larger, deeper body shapes. Species with this body patterns tend to live in slow-moving waters, and really excel in life in deep pools and impoundments. If streams and rivers are dominated by those species, and there are fewer fish living in swifter currents, then it could reduce predation on certain insect species which, big picture, will disrupt the food web.
And, 150% just represents the AVERAGE change in functional diversity. They also found that changes were higher than average when the invading species was truly nonnative (like, maybe from a different country, as opposed to from a neighboring watershed), and when the original ecosystem only contained a few species.
So, why bring this study up on a trout blog? I frequently like to imagine what stream ecosystems are going to look like in 200 years. Right now, we are already seeing rapid changes in the species diversity in stream ecosystems. We’ve stocked a lot of nonnative fish, to the point that it is sometimes difficult to know when a species is truly native anymore. Of course we know the history with brown trout. But, smallmouth bass? Nonnative. Channel catfish? Mostly nonnative. Bluegill? Guess what- mostly nonnative. A lot of these species mix with native species in cool and warmwater rivers and, as climate change advances, we continue to see these species creep further into the headwaters in search of cooler water. It’s now not that uncommon to find bluegill and brook trout together. These two species aren’t direct competitors, but how are those invasions going to change the stream ecosystem as a whole?
I guess only time will tell….
*Note: Content in this post is my own and may not reflect the opinion of the manuscripts' authors or the agencies they represent. I encourage you to read the manuscript, found here, so you can contribute to the discussion