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.
Ben Kline, undergrad extraordinaire, graciously offered to pick up my slack and do a few blog posts over the next few weeks. Ben has been working in the lab for almost a year now, and taken leadership on a project looking at individual variation to heat stress. Results of the project are still pending, but we’re introducing him to a whole new side of science- professional conferences. In this post, Ben talks about his first impressions of an American Fisheries Society (AFS) meeting, which he presented at in February. He did so well that he's packing his bags for the National AFS meeting in August in Atlantic City.
A couple of weeks ago I was lucky enough to give my first oral presentation at a professional conference on fisheries science. It wasn’t my first ever presentation, as last fall I attended the Susquehanna River Symposium at Bucknell University. If you follow The Troutlook on Twitter, then there is a good chance you saw my first crack at a research poster that I attempted to pull together for the conference (or perhaps you were able to pick out the glaring typo instead). The event was quite memorable, and I was pleased with how everything turned out. The poster presentation was a great way to get my feet wet in the fisheries scene, and I thoroughly enjoyed meeting and talking with other people that were interested in the same realm of science as me.
Making the poster and hearing feedback was something that also helped me to reflect on my current and potential future research experiences. As people began to talk to me about my project and ask questions, it became evident that, although I had already spent months working on my project, I still had significant knowledge gaps about all of the moving parts behind our experiment. This experience was somewhat disappointing, as I felt that I had not learned very much in my time working on the project, but also simultaneously quite motivating in a sense that there was a bit of urgency for me to get back to the lab and keep working on the project.
I left the symposium with some thoughtful critique and some questions in need of answering. Upon returning to the lab after some time for the winter holiday, another opportunity presented itself to me. A few weeks prior I had submitted my first abstract to give an oral presentation at a local conference. When I logged into my email I had discovered that my abstract was accepted and I would get a chance to speak at the annual meeting of the Pennsylvania Chapter of the American Fisheries Society. Upon sharing the news with Shannon, we immediately got to work. I had never before given a professional talk about my research and I knew that there would be a lot for me to learn. I prepped my talk and meticulously edited my PowerPoint until I was pleased. When it finally came time to give my practice talk to our lab I knew that there would be plenty of comments, but I was eager to learn and improve in any way that I could. To my surprise, my talk was received warmly by the other members of the lab. With the meeting coming up in just a few short days, I continued to refine my work until the story came out exactly how I wanted it to.
The morning of the conference was a big groggy. Getting up at 4:30am and then taking a 2 hour drive in subfreezing temperatures is not the most glamorous way to start the day, but I was excited nonetheless. We arrived at the conference center and got things set up. I had the chance to chat with a few of my classmates from Penn State that were in attendance while we waited for the show to begin. There were about 100 people in attendance, a healthy mix of managers and academics with few students- and even fewer undergrads. I was a bit nervous to give my talk, and being the first person to go wasn’t very inspirational. But a curt nod from Shannon was enough to motivate me towards the podium and the rest was downhill from there. The talk went quite well, and only one person was asleep, so I would consider it a success. With a major weight lifted from my shoulders I had the opportunity to sit back and enjoy the rest of the conference for what it truly was. I had plenty of opportunities to listen to other talks about research that is going on in the fisheries world. As a future graduate student, it was really helpful to hear what kind of projects other people are working on so that I could better define my interests. I was also pleased to have the chance to meet a number of other scientists and managers and hear about their experiences firsthand.
Through it all I was certainly able to learn a number of valuable lessons. From my first attempt at a research poster to my second attempt with the oral presentation, I was able to identify that I maybe didn’t fully understand my project to the best of my ability, and that was okay for the time being. Having a hard time putting your work into words was a great way of identifying what parts of my research I should spend some time becoming more familiar with. After all, it is one thing to try to understand something yourself. However, being able to not only explain, but also really convey the essence of your research to someone else is something that is truly difficult to do, which brings me to my second lesson. Being a good presenter is about being a good story-teller. The more clear and vivid of a picture you paint for your audience, the better your talk will be as a whole. I spent countless hours thinking about the story that I was trying to tell with my presentation and as a result, the final product was much different than the original. It isn’t about having perfect transitions or the most articulate vocabulary in every instance, but instead about finding common ground that is relevant and meaningful to your audience and using that as a way to leverage the most important parts of your research into what you are trying to say.
I’m happy to report that after months of studying (and neglect of this blog), I successfully passed my comprehensive exams this week. Over the course of a 40-hour written and 3-hour oral exam, I delved into everything ranging from statistical models, population genetics, adaptive management, and the history of ecology. My brain is mush.
But, in the middle of my exam, I took one day to attend the Pennsylvania Chapter of the American Fisheries Society to present the results of our study on hatchery and wild brook trout interbreeding. I know I’ve been holding those results hostage for a few months, but now that I’ve started spreading the word and our manuscript is nearly published, I think it’s about time I let you all in our secret. Drum roll please…..
In Loyalsock Creek, hatchery brook trout don’t seem to breed much with wild brook trout.
Are we sure? About as sure as we can be.
How can this be? We don’t know exactly, but we have guesses.
Let’s step back a little and digest this study. Throughout their native range, hatchery brook trout are commonly stocked in streams frequented by anglers to increase the probability of catching a keeper trout. Stocking programs are largely successful in accomplishing that goal, but yet often remain controversial because of the possibility that hatchery trout might breed with wild trout. The process of wild and hatchery interbreeding is more formally known as introgression.
Why do we care about introgression? In short, introgression can decrease wild population reproductive success and increase the likelihood that a wild population will be extirpated. The mechanisms behind this response are a bit complicated, and have been covered in another blog post. But, it largely centers on the fact that fish used in the hatchery system are so genetically different than wild fish (especially when the focus of the hatchery is in recreational stocking…more on that in other blogs). The last time a wild fish was brought into many hatcheries was 50-100 years ago. In that time, humans have bred hatchery fish to grow really fast, really large, and produce a lot of offspring. While these traits produce a great hatchery fish, it often makes hatchery fish very unsuccessful at life in the wild. So, when a wild and hatchery trout introgress, their offspring often have low survival and low reproduction. To put another way- think of offspring as the average of their parents. The average of two wild fish is usually going to be far superior than the average of a wild and hatchery mating.
It only takes a few generations of introgression for there to be a noticeable decline in population size, and for the risk of extirpation to rapidly increase. However, much of our understanding about introgression in brook trout is borrowed from studies of salmon, and in situations where there was a large-scale accidental release from a captive facility and/or where a stocking program was terminated 10-20 years ago. There is very little information about introgression in a ‘typical’ stocking reach- where stocking is still ongoing, and has been occurring for 10-20 years. So, prior to this study, we didn’t really have a great idea on how active stocking might influence introgression in wild brook trout streams.
And, we are just as surprised as you when our results showed very low rates of introgression. We surveyed 30 sites across the Loyalsock Creek watershed and analyzed genetics for 1742 fish. Only 97 of those fish (<6%) had evidence of introgression. And, it’s worth noting, our methods were very sensitive, so if anything we overestimated the number of introgressed fish.
Now, this isn’t a call to go out and stock freely and openly. One troubling find was that we did find introgression at sites several miles away from the closest stocking location. Often times, stocking is justified because it doesn’t occur directly on top of a wild brook trout stream. However, our results suggest that the impact of stocking can extend far beyond the spatial scale of direct stocking efforts. How stocking could influence wild trout populations needs to consider not only the status of the stocked stream, but also streams nearby.
Second, it’s important to keep in mind that we did not account for how stocking could influence wild trout reproductive success. Does competition for food and space with hatchery trout decrease wild trout reproduction? Do wild trout readily attempt to breed with hatchery trout, but offspring die before we are able to sample them? We’re not sure, but both of those scenarios are plausible non-genetic effects of stocking that our study cannot address, and that would still result in declines in wild population survival.
Why introgression seems to be substantially lower in our study relative to other studies of trout and salmon is a bit of a mystery. It’s possible that stocked brook trout die (either through harvest or natural mortality) quickly after stocking. We know there is some truth in this, as stream surveys rarely find stocked fish even a few months after stocking. It’s also plausible that there is an environmental gradient over which stocking is more or less possible. Because we did not find much introgression to begin with, we can’t really test hypothesis about how the environment may influence introgression. However, we did find some patterns where introgression did seem marginally higher at sites with higher densities of wild adult brook trout, and where pH was higher and temperature low. In short, it seems (though very preliminary and without high certainty) that robust wild trout populations may be a little more resistant to introgression.
Overall, our study suggests that until a better understanding of the factors that influence hatchery and wild trout introgression are known, a cautious prescription of hatchery stocking may still be warranted.
I have, and will continue to be, sparse with my updates. I’m in one of the most dreaded times of a Ph.D. student’s tenure- the preparation for, and eventual taking of, my comprehensive exams (colloquially known as comps).
For those unfamiliar- comps are arguably the biggest hurdle that stand between a Ph.D. student and graduation. No two people have the same comps, but for me it will entail a 40-hour written test taken over the course of four days and a three-hour oral exam. But, it’s not the length that’s daunting. It’s the topic. Science. Know anything and everything about science (and statistics, because good ecologists need to know what to do with their data after it’s collected). Just about the only way to prepare is to read as many textbooks, articles, and online guides as possible. So, read I must. Every day, all day, for the next month. Panic hasn’t quite set it, but I can tell it’s getting close.
While comps definitely add a bit of pressure, I can’t say the experience has been entirely miserable so far. It’s easy to get hyper-focused on one project and lose focus of how your work fits into broader ecological contexts. So, it’s been fun stepping back and thinking more broadly outside of hatchery introgression, which has been the object of all of my attention lately (but which we did finally submit for publication). And, I’ll write about all of that after comps. Promise.
For now, in all my readings I stumbled across one very short article that seemed perfectly fit for this blog. No long explanation required, but a research finding I suspect many of you will be interested in. The topic is one of my favorites: nonnative fish invasion on native populations. So often I hear people argue something to the effect of ‘nonnative fish are not causing declines in native populations, but simply taking over as native populations are dying off due to climate change, habitat loss, etc.’ To put another one, people often think that nonnatives are REPLACING, not DISPLACING native fish.
If this were true, if nonnative fish were simply replacing natives, then there wouldn’t be a lot we could (or probably should) do about it. When a population of a species starts declining, it opens space in the ecological niche that usually needs to be filled in order to maintain ecosystem functioning. It’s like a job opening- if Debbie was going to quit, it’s better that someone fills the position rather than just leaving it vacant and hoping Debbie returns. Replacing Debbie would be like filling the empty ecological niche.
But, what if Debbie had no intentions of leaving and is being forced out? In this case, Debbie would be displaced. The intruder will likely fill some of the same roles Debbie left behind, but may also neglect certain tasks. As we all know, two employees with the same job description rarely have comparable work effort and quality. The intruder is going to leave some of the niche open.
Bringing this back to fish, it’s really difficult to determine if a nonnative species are replacing or displacing a native species. If we were to track the number of fish of each species over time, we’d likely see that one species (usually the native) was increasing and one (usually the nonnative) was decreasing. But, that is not evidence for either replacement or displacement. If the nonnative species was absent, the native species may still decline due to habitat loss, genetic collapse, or overharvest. Or, it may thrive despite all the aforementioned stressors. The only way to know for sure would be to do several very controlled experiments where we artificially added or removed fish from streams and then monitored their populations for several generations. But there are time constraints, and largescale changes to species communities are generally frowned upon in conservation.
So…enter statistics, where we can model the relationship between the abundance of each species, time, and environmental variables to determine how each species effects one another. If that sounds vague, it is. But, the details aren’t worth describing here. It’s just worth noting that a researcher from Japan recently used these models to investigate how invasion of nonnative brown and rainbow trout influenced the abundance of native white-spotted char (a close cousin to brook trout) using data collected over 15 years.
And his findings? Nonnative trout clearly DISPLACE native trout. Moreover, rainbow trout also displace brown trout, so not all nonnatives are created equal. If you think about Pennsylvania, right now brown trout are outcompeting (whether it is replacement of displacement, we don’t know) brook trout. In the future, could we see displacement of brown trout by rainbow trout? Certainty possible.
Perhaps more noteworthy, there was a significant time lag (8-13 years) between the initial invasion of nonnative trout and displacement of white-spotted charr. But, once displacement started, it was achieved rapidly (just a couple years). This suggests that monitoring efforts following invasion may have to extend for several decades before the effect of invasion are realized. It’s not enough to make conclusions about invasion based on only a few years of data, and certainly not enough to make inferences on the cause (be in replacement or displacement) with such limited information.
*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