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
Time flies when you’re working on a dissertation. I turn around and it’s suddenly the end of the semester and I haven’t posted any updates in over a month. Oops.
Truth be told, there hasn’t been a lot to update on recently. Preparing for outreach events had me spending more time photo shopping in Microsoft Paint than running data analysis in R. But, Ben and I put together some impressive posters, so I consider that time well spent. And, we showed them off this past week at an Earth Day event at the local elementary school.
I’ve also taken the show on the road, and have been visiting several chapters of Trout Unlimited to present the hatchery-wild brook trout interbreeding (or introgression) results that I discussed in a previous blog. At first I felt a little guilty about making introgression the main topic of my talk because I thought most everyone in attendance had already read my blog post. But, as science turns, after we submitted the manuscript for publication- and after we thought for sure we had covered all of our basis with analyses- reviewers unanimously wanted to see another analysis. Of course.
Truth be told, we were actually happy to do the requested analysis. Simply put- they wanted us to quantify how introgression varies across different habitats. Is introgression higher in sites with higher temperatures? Lower pH? What about introgression rates in small vs. big streams? Does distance to a stocking location influence introgression? These are all great questions because they can help us understand if there are site-level characteristics that make a site more likely to have higher rates of introgression. And, if fish are more likely to introgression in certain habitats, then we can use that information to potentially adjust our stocking protocols.
Unfortunately, while there was no doubt this analysis was worthwhile, we knew before we started crunching numbers that none of the results would be statistically significant. If you remember, less than 6% of all fish we tested showed signs of being introgressed. And, most fish at any of our 30 sample sites assigned to pure wild origin. Without the presence of introgressed fish in our study, we weren’t going to be able to find strong relationships between habitat and introgression. It’s like trying to quantify elephant habitat in Pennsylvania- if the elephants aren’t here, we can’t really quantify their habitat.
But, because there are so few studies of introgression on stream trout, we knew that we could still use the results of the analysis to start building hypotheses about habitat variables that could matter. So, that’s what we did. We analyzed whether the probability of an individual being introgressed was related to eight “site-level” and three “watershed-level” habitat measures. The site-level variables includes measures of water quality and physical habitat that you would see if you were standing in the stream like pH, dissolved oxygen, and stream width (and we got lucky here, because all of that data was collected by Susquehanna University and the analysis would not have been possible without their willingness to share data). The watershed-level variables were those I measured back at the computer and were things like watershed area and landuse.
Like we expected, none of our models implicated any of our habitat variables as a smoking gun that increases introgression- all models showed a statistically insignificant relationship between introgression and the 11 habitat variables. But, a bit to our surprise, we did have a few variables that approached significance. Again, this was surprising because we had so little introgression in our data, and so even a variable that trends towards significance is worth a second look.
Probably not ironically, the variables that trended towards significant were also variables that have been suggested in other studies of lake-dwelling brook trout and stream brown trout as being modulators of introgression. It seems there is a consensus among studies that introgression rates are lower in larger streams, and at sites with low pH and higher adult brook trout densities. This makes some sense as higher wild trout densities increase competition (which likely decreases reproductive success of stocked fish) and larger streams have more stable flows that can help promote a large, healthy wild population. It’s suggested that pH might also be an important predictor of healthy wild trout populations, as macroinvertebrates densities are often higher in streams with higher pH.
So, at this point, these results can’t yet be used to really direct stocking efforts. They really just point to a need for more directed studies of introgression in stream trout. But, it does make you think. Most of the time we only stock streams without brook trout, or in streams with “marginal” wild populations. Those “marginal” populations, which tend to be smaller in size but existing in decent habitat, may be the populations that are most vulnerable to introgression. So, by trying to avoid wild-hatchery interactions and stocking in marginal populations, could we actually be increasing the probability of introgression? Again, we just need more data to tell.
He's back. While I work to meet a few deadlines, Ben is filling in again and providing some more perspective on his experience as an undergraduate. Hopefully this is just a start, and he'll be providing more details in future posts as he navigates many "firsts" in his career as a fisheries biologist. Notably absent from his description is any mention of full his calendar became after he started working in the lab, and how much sass he receives from me daily. I'm giving him the true fisheries experience.
Getting involved in research as an undergrad can certainly feel like a daunting task. When you first arrive at college, no matter what school or major, it is undoubtedly going to be a lot different than anything you have ever experienced before. In the midst of trying to make friends, adjusting to college classes, and trying your best to get involved, thinking about your future is something that often gets thrown on the backburner. Nonetheless, when the time comes to take on a new challenge, it can be difficult to know where to start. Luckily, I am here to share my struggles and triumphs in finding an undergrad research position so all of you can live vicariously through me.
When I first decided that I wanted to get involved in undergrad research, the first person I went to was my academic advisor. At a regular advising meeting one day we were just discussing my courses for the upcoming semester and I brought up the possibility of starting to get some volunteer hours in a biology lab. Her recommendation to me was to go online to faculty webpages and start looking for professors doing research that might interest me. I took her advice and began searching for what I hoped would be my future home. While this was pretty interesting at the beginning, freshman me had no clue about half the research I was reading about. And with riveting topics such as “atypical heterotrimeric G protein Y sub-unit and guard cell K channel regulation in morphological development” and ”chronic unpredictable stress causes long-term anxiety”, I think I was starting to develop some long-term anxiety of my own. Not to mention the nightmare that is trying to meet with faculty that have schedules that are equally or more busy than your own class schedule.
There is nothing more awkward than walking into the office of a professor you have never met before and trying to simultaneously impress them while also trying to pretend like you know more about a research topic than you actually do. After my fair share of uncomfortable meetings with professors that were studying nothing close to what I was interested in, I decided to talk to an instructor that was teaching a class that I was taking in my major about research opportunities. Meeting with her was a great way to become exposed to researchers that were doing work that was more relevant to what we were studying in class. While I was disappointed that she was not able to offer me a research position in a lab of her own, I left her office a bit more interested in continuing my search. I sent out another round of emails to some of the people that she suggested to me and eventually heard back from two of them. This time when I met with the each of the professors I did my best to be straightforward about what my skills were and what I was hoping to get out of my experience.
Within the next few weeks I had heard back from both of them with two very different offers. The first of which was the potential for a full-time position, 40 hours a week, for the entire summer sampling in local state parks. The second offer was to work part time in the summer on a brook trout project. I think by now it is obvious which choice I made, but there were a few other considerations that I had to make when choosing a position. I knew that there was no way that I would be able to afford to spend the summer at school without another part time job. I did what I thought at the time was “biting the bullet” and declined what seemed like it would be a really amazing opportunity and opted for the part time position so that I could work part time at the university advising center in order to save a little bit of money. I could not have been happier about my choice.
Finding an opportunity to work in research as an undergrad forced me to make a lot of difficult decisions and really reflect more seriously about what I wanted to do in the future. It is extremely difficult to make choices for reasons based on things other than simply academics, but as is the nature of life that we often have to choose between what we think is best for us and what is actually feasible. In this case, everything ended up working out quite well for me. After I took some time to get oriented to the undergrad research life, I was able to find a fair amount of success with the help of my mentor and other lab-mates. Through undergrad research I got to experience my first taste of field research. It was really engaging to see that skills that are so often talked about in the classroom coalesce into a real-world application used by scientists every day. As you heard in my last post, my research experiences have been invaluable when it comes to networking and developing effective science communication skills. I am also so grateful for all of the opportunities that have been made available to individuals like me through funding offered by a number of locations on campus that support undergraduates in research. It is thanks to these generous contributions that I am able to continue to perform research and better define my interests as I learn more and more about the world of fisheries science. I hope that one day in the future I can reflect again on my undergraduate research experience and how it has shaped me into the person that I am, but for now I will just sit back and hope for the best.