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
Fish don’t usually make the list of charismatic species. They’re slimy and brown. They don’t have any immediate characteristics that are akin to humans. And, they’re hidden below the water, where you may never see them without a visit to the aquarium.
I think that’s what makes fish conservation challenging. On a Sunday drive to the supermarket, you could pass right next to a stream containing an endangered species and never even know it. It’s fairly easy to find images and videos of polar bears searching for food, panda populations declining, and stories on elephant poaching. But, when it comes to fish, even professional cinematographers often shy away from the challenge. It makes my job tough, because it’s hard to “sell” people on conservation of an animal they can’t appreciate outside of recreational angling.
Truth be told, as a biologist it’s also easy to forget the species you work on is more than just numbers on the computer. I got into this profession after years of conducting behavior observations on trout, and becoming fascinated by the social dynamics and personalities of fish. They may not be cuddly and furry, but fish have all the same social dynamics as the other charismatic megafauna that are the poster children for wildlife conservation.
This week, Ty and I travelled to Loyalsock with the mission of getting some pictures of fish. We’re always giving presentations to kids, adults, scientists, and non-scientists, but we take few pictures of us working, and even fewer of the fish in water. And, as the adage says, ‘a picture is worth a thousands words.’
A picture is also worth thousands of dollars. Trying to capture photos in dark, coldwater means you need wetsuits, snorkeling gear, and fancy cameras. Thankfully, Ty was able to use some grant money to fund this excursion, and we hit the water in search of brook trout. Unfortunately, flows were pretty high that day, making it difficult to hold yourself in place, and to see fish more than a few feet in front of you. And, only one camera was operational that day, so I just crawled around the stream while Ty took photos.
But, what I saw reminded me of why I love my job. Having sampled this stream many times, I had a good guess on which pools would be good for snorkeling, which was key because the stakes for snorkeling an empty pool are a little high. It takes trout 10-20 minutes after you arrive to come out and resume normal activity, and the water is cold. While the wetsuit helps, it’s the kind of cold you never really get used to, but that ironically you’d rather stay submerged in rather than get out, heat back up, and then get back in.
The day started slow, and I was a little nervous I might not find fish with the high flows. But, I eventually found a nice pool and just settled on staying there until I saw something that moved. I nestled into an area of lower flows, gripped onto two rocks and waited. And waited. And waited. My hands were starting to go numb from the position I had then in, and right as I went to reposition I saw what looked like a tail right at the end of sight. I slowly inched forward enough to see not one, but two 6-inch brook trout. I stayed there for about minutes watching them feed before moving up to a new pool to start the process all over again. That next pool had even more fish, some swimming right next to my face, attempt to eat my glove, and fighting each other from their territories.
We ended the day by going out to mainstem Loyalsock, where we were rewarded with warmer temperatures, large brown trout, huge largemouth bass, and a few smallmouth bass that were happy to follow us around as we were overturning rocks.
Here’s a few photos of the day.
This week is a guest post from Megan Schall, a long-time Wagner lab member who is soon to fledge and join the ranks of the gainfully employed. The Wagner lab has been stable for the last four years with few coming or going. I have to admit it's a little weird for everyone as some doors close for some (like Megan) and others open (I'm getting two new labmates this summer!).
For those of you who don’t know me, my name is Megan Schall and I have been a member of Ty Wagner’s lab with Shannon for several years now. My post today is not a technical one, but more of a feel good post. I recently finished my dissertation and am preparing to transition from a graduate student to a professor (Wow, that sounds a little scary!). I spent the past five years or so of my graduate career pouring my heart and soul into my research studying smallmouth bass in the Susquehanna River Basin. If you would ever like to talk anything smallmouth bass from movement, disease, genetics, population trends or anything related to fish health/ecology I am always happy to talk. Yet today’s post is not about that either. It is about reconnecting with one’s inner self and at the same time passing the baton to the next generation. I will give a small disclaimer that this post may be a bit sappy for some readers.
I recently sat on the bank of one of my prized smallmouth bass sampling sites on Pine Creek reminiscing. I had spent many hours, days, and what sometimes felt like years hiking up and down the banks of this creek. I tracked fish as they swam in and out of the creek from the larger connected river and was fascinated by what I had learned from this system. I went back to Pine Creek recently for what I believe to be one of my very last smallmouth bass surveys of my academic career. I did not go alone, but with a great research team (small army) that has been involved in the research for many years. I also brought Ben Kline (our resident undergraduate researcher) with me to offer him a change of scenery. I have sampled and been a part of dozens of smallmouth bass surveys, but this was a brand new experience for Ben. My goal on one of my very last surveys was to get Ben involved. As a result, I found myself with ample free time on my hands allowing me to reconnect with nature.
My interest in ecology has always been a part of who I am as a person. I would describe myself as a naturalist at heart who has always intrigued by the natural world while trying to understand ecological relationships. In the hustle and bustle of life and working to complete my graduate degrees, I often find myself far removed from that. I spend much more time at a computer these days than outside enjoying nature. So as I sat on the bank of my favorite stream, I felt in that moment, I was able to truly appreciate it for what it was worth. While watching Ben help collect fish, I began to rediscover myself. For a while, I stared around just taking in the view and listened to the chorus of birds in the background. But then I started to dig a little deeper. I took pictures of water droplets hitting off of the water’s surface and noticed how glass-like the water appeared with each ripple. Then I went beneath the surface and flipped over a rock to find a small water penny. The water penny moved across the surface and I was intrigued to think of all we miss without digging a little deeper. In that moment, I was able to reconnect with why I became an ecologist in the first place. I was curious and excited all over again. I think in our busy lives, we can all get a little caught up in our daily routines and forget why and who we are underneath everything. On this day, I was able to pause just for a short amount of time and reminisce. It was exactly what I needed.
I also was able to think about the future, both my own future and that of our future scientists. It was more important for me to get Ben experience and to pass that baton then for me to be involved in every moment of my last survey. I even ended up recording fish health data which is usually passed off to the new unexperienced member of the crew. I did not want that experience for Ben, but rather for him to learn how to perform all parts of a fish health survey. Don’t get me wrong, it is a good skill to learn how to record data, but if you only have one day to get an experience, it definitely is not the best way to maximize what you can learn. Good thing for Ben, they were successful collecting the fish today and our survey went according to plan. While I recorded notes, Ben was able to jump in and hopefully he can tell you a little more about what he learned in a future post. I think we all need to be aware of the future and realize that it is not always about what we can individually do, but the mark we can leave on others as well. If I can inspire a few others to want to inquire more about the natural world, then I have done a much better job than just doing the work myself and in turn, my impact will be much larger. I hope that like the ripples on the water’s surface today, I can have ripples that reach far from all of those I am able to teach and inspire. As I sign off on my time here at Penn State, I am thankful for all of those who have inspired me including my family and coworkers. We have had such a great time over the years working together and laughing our way through the day.
Well, I think that is enough of the feel good stuff for one post. I hope Ben will share more personal details about his experience and what he learned while out with us. To end this post, I want to encourage all of you to take a moment to get lost in nature and enjoy the beautiful streams throughout the state of Pennsylvania and across the country. I want to share with you some of the best spots in my favorite stream (Pine Creek) in case you ever find yourself in northcentral Pennsylvania.
My top spots/activities in Pine Creek include:
1.) visit the Pennsylvania Grand Canyon- http://pacanyon.com/ ,
2.) walk or bike on a portion of the rail trail- https://visitpottertioga.com/explore/attractions/pine-creek-rail-trail/ (I am particularly fond of the Ramsey, Bonnell Flats area of the trail),
3.) visit Little Pine State Park- http://www.dcnr.pa.gov/StateParks/FindAPark/LittlePineStatePark/Pages/default.aspx ,
4.) visit the DCNR Tiadaghton State Forest Office in Waterville, PA for a great view and resources- http://www.dcnr.pa.gov/StateForests/FindAForest/Tiadaghton/Pages/default.aspx ,
5.) fish for a variety of fish species including smallies and trout in the creek and tributaries -(Slate Run is a nice tributary for trout fishing and while you are there be sure to stop in at the Slate Run Tackle Shop for some good fishing intel- http://slaterun.com/default.php ,
6.) try kayaking –there are quite a few spots to get in and out - http://www.pinecreekvalley.com/PineCreekValleyCanoeAccess/CanoeAccess.asp,
7.) if you get hungry, the Waterville Tavern is a great spot to grab a bite to eat- http://watervilletavern.com/menu/.
There are many other areas throughout the state and country with exciting opportunities waiting for you. I challenge you to find your own favorite places and don’t forget to enjoy nature in its beauty every now and then. Capture that memory and keep it close, especially when the hustle and bustle gets in the way as we all know it will once again.
Whether you love them or hate them, once a nonnative fish species invades a stream or river, it is often impossible to get them out. Sometimes these colonization events are entirely accidental, like the Eurasian-native round goby that is thought to have been released in ship ballast waters sometime in the 1980s. Other times, nonnative introductions are deliberate, like the stocking of nonnative trout throughout the United States.
While present-day stocking efforts reflect the desire to have fish in certain locations, the distribution of nonnative trout largely represents the ghosts of managements past. Today, it is unlikely (I hope) that we would stock nonnative brook trout in the Rocky Mountains where they readily outcompete native cutthroats. Likewise, we might think twice about the extent of brown trout stocking on the east coast if we knew how readily they displace native brook trout populations. However, at the turn of the 20th century, we didn’t know better. Nonnative trout stocking became the status quo and, to a large degree, it set the precedence for modern-day fish management.
But, as science evolves, and as managers, anglers, and conservationists seek to find a balance between native fish conservation and recreational fishing, we’re often find ourselves in a position of regret. We now know the threat nonnative trout can have on native species; however, there is very little we can do about it. Manual removal of nonnative trout is often ineffective because it is labor intensive (read: expensive), and requires managers to electrofish large stretches of stream and pick out natives from nonnatives. It’s also possible to chemically remove undesired fish, but this method of removal also kills native fish and can have other ecosystem-wide impacts. And, in the end, neither manual or chemical removal prevents a nonnative trout from outside the study reach moving into a managed stream and undoing all the efforts. With our hands seemingly tied, a lot of people now argue for management and conservation of nonnatives, quoting that “nonnatives are the future of the fishery”, that “something is better than nothing,” or “let’s do the best with what we’ve got.”
But, what if we could rewind the clock? What if we could actually eradicate nonnatives? Manual and chemical removal are unlikely to be effective eradication measures but, ironically, stocking might just be a saving grace for some native trout populations.
The trick? Stock “supermales”- male fish that are only capable of producing male offspring, In theory, over several generations of reproduction with supermales in the population, the sex ratio of a population would become so far skewed towards males that the population would not be self-sustaining and would collapse.
So, how do supermales work? Recall from basic biology that all females have two X chromosomes, and all males have one X and one Y chromosome. During reproduction, females contribute an egg with an X chromosome, and then offspring sex determination is decided by whether the egg is fertilized with sperm that has an X or a Y chromosome. In supermales, all sperm have Y chromosomes, and so all offspring from supermales are males. So, stocking supermales is basically an effort to remove X chromosomes (and thus females) from a population.
It sounds difficult, but the production of supermales is actually relatively easy and has been used in aquaculture for decades. Producing a supermale requires feeding normal fish estrogen-infused food, which causes males to produce eggs rather than sperm. When hormone-treated males (with eggs) mate with untreated males (with sperm), about 1/3 of the offspring will only have Y chromosomes (the other 2/3 will have at least one X chromosome). If you mate the Y-only feminized males with Y-only supermales together, 100% of the offspring with be supermales that only have Y-chromosomes and, when stocked, will only produce male offspring. And, because supermales themselves were never exposed to hormones, there is no concern about consumption of stocked fish or introduction of chemicals into the environment.
Seems like a win, right? Now that hatchery production methods for supermale trout have been ironed out, it seems like the possibilities could be endless. However, now there is another problem. Survival and reproduction of stocked trout is often very poor compared to wild counterparts. And, for supermale stocking to result in complete eradication of a nonnative trout population, supermales have to comprise a relatively large proportion of the spawning population.
Fisheries managers in Idaho are now in the process of evaluating survival and reproduction of supermales, and the potential efficacy of supermale stocking for nonnative species control. Simulating possible scenarios, they determined that stocking juvenile supermales could result in complete eradication of nonnative brook trout populations in less then ten years, with faster eradication rates occurring when stocking is combined with manual removal of wild fish. This was a promising result; however, another study of actual fish populations showed that stocked adult supermales had low survival and reproduction compared to wild counterparts. So, while the supermales did reproduce (which is encouraging), only about 4% of wild offspring had a supermale father.
For supermale stocking to be an effective method of population eradication, managers will have to find a way to increase reproduction of stocked supermales. How to achieve this goal remains a little uncertain. It can’t be achieved by simply stocking a higher density of supermales. Higher stocking densities are known to increase mortality of stocked fish, and mortality of stocked supermales has already been shown to be high. However, it may be that a combination of stocking and manual removal could increase survival and reproduction of supermales, which could increase the probability of eventual eradication. Or, survival and reproduction may be higher if juveniles are stocked rather than adults, or vice versa. All of these hypotheses are currently being tested to improve supermale reproduction in Idaho streams.
I think it’s also important to note that so far the end goal of supermale stocking has been complete eradication. However, even if eradication is not possible, supermales may still be effective for suppression of nonnative populations. This could help preserve native fish populations while still allowing for nonnative fish persistence. However, regardless of whether the goal becomes eradication or suppression of nonnatives, the success of supermale stocking is also going to depend on management of adjacent tributaries. If stocking continues in nearby tributaries, then movement of nonnative fish back into managed waterways will ultimately make supermale stocking efforts futile.
So, are supermales too good to be true? For now, 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 and here, so you can contribute to the discussion