Graduate student Max Moran, a master’s degree student in the labs of Drs. Tomas Höök and Peter Euclide,
received the Norman S. Baldwin Fishery Science Scholarship at the International Association for Great Lakes Research conference in early June.
The Baldwin scholarship, sponsored by the Great Lakes Fishery Commission (GLFC), is given to graduate students conducting research pertaining to Great Lakes fisheries. The award, which is named in honor of the first executive secretary of the GLFC, came with a monetary prize as well as the opportunity to present his research at the conference.
“Overall, the conference was a fantastic experience. I got to share my research and get lots of great feedback from amazing researchers, which was really incredible,” Moran said. “Some people gave me suggestions on potentially how to look at things I have been struggling with analyzing. Some other researchers reached out about potentially collaborating with myself, Tomas Höök and Peter Euclide in the future. I was really excited to see that people not only were interested in my work but wanted to potentially get involved themselves. That was really cool and getting selected for the scholarship was really exciting. When you’re in grad school, having those little ego boosts are always helpful in continuing the grind of grad school.”
Moran’s research topic “Ecomorphological Diversity in Lake Charr (Salvelinus namaycush) Morphology and Visual Sensory System at Klondike Reef, Lake Superior” is the culmination of his interest in all things aquatic as both a high school and undergraduate student as well as his work as a research technician at the University of Illinois’ Sam Parr Biological Field Station, which led him to study at Purdue.
The Backstory
The Richmond, Virginia, native studied environmental science and environmental thought and practice at the University of Virginia, since a true aquatic sciences major was not available. The environmental science major included more “hard sciences” and required a lot of ecology, hydrology, geology and atmospheric science courses. UVa then began offering the environmental thought and practice major, which was “designed to essentially give you a more anthropocentric view on the different issues we were working with.”
In order to truly focus on his interest in aquatic ecology, Moran turned his focus outside the classroom to research opportunities.
“I got involved with Dr. Mike Pace, one of the main aquatic ecologists that worked there, and was lucky enough to have him and his PhD student at the time Spencer Tassone take me under their wings,” Moran recalled. “They mentored me and helped me learn how to be a researcher. My advisor at the time, Dr. Karen McGlathery, who was primarily an estuarine ecologist, also really helped me to continue to develop my love for aquatic sciences.”
After earning his bachelor’s degree with the double major in 2022, Moran took a job as a research technician specializing in aquatic ecology and fisheries biology for the Illinois Natural History Survey based at Sam Parr Biological Field Station. While there, he conducted research on sportfish ecology in southern and central Illinois and also was part of behavioral assessments of the Lepomis genus (or true sunfish). That position proved to be pivotal in shaping Moran’s future research interests and in bringing him to Purdue.
“The cool thing about that job was that I got to be a part of a ton of different research projects at once,” Moran said. “The overall project was funded to look at the effect of different regulations on the management of different sport fish species, particularly crappie. But, what actually ended up pointing me in my current direction was a project I worked on with Dr. Mike Nannini. He is primarily a behavioral ecologist and he was doing really cool work on different behavior types in different sunfish species. Getting to see how these very closely related species differ greatly in terms of behavior got me really interested in that evolutionary biology route.
“What actually ended up being the most interesting for me in that research was seeing how even within the same species there was this crazy amount of diversity. Seeing how two Bluegill could be just as different as a Bluegill and a Redear (sunfish), that interspecific diversity, made me realize that I was interested in that type of research.”
An advertisement for a graduate student in Dr. Tomas Höök’s lab at Purdue caught Moran’s eye. And being
familiar with Höök and Dr. Peter Euclide’s previous publications, he applied. A couple interviews later, he was a member of the lab.
“It just seemed like a really cool opportunity to play a big part in a massive, overarching project,” Moran explained. “This research has numerous collaborators from different research institutions. Just in terms of co-authors, we have seven different institutions represented. It is really cool getting to work with all of those different groups.”
The Research
Moran’s research studies the ecomorphological diversity in Lake Charr (commonly known as lake trout) in the Klondike Reef area of Lake Superior.
Ecomorphs are a subgroup of individuals within a single species that differs from others ecologically and morphologically. They may utilize different habitat areas. They may differ in terms of their body shape or coloration, fin size or eye color. Physiologically, they may have different hormone levels or other biochemical traits. They also may have different dietary preferences and life spans.
In this research project, Moran and his collaborators are utilizing multiple methods to assess each ecomorph’s characteristics.
The first step is visually assigning ecomorphs between the four common varieties – leans, siscowets, humpers and redfins – based on photo evidence. Researchers take a standardized side profile image of the left side of each fish they capture to study. The picture includes a ruler inside the image that allows the scale to be standardized between images to allow accurate comparison. Photos are then marked with dots in specific areas along the fish’s body, which creates data to be used and compared through a mathematical technique called thin plate spline.
“With the morphology, we are basically trying to confirm what we see out in the field,” Moran shared. “Thin plate spline is a type of math that essentially summarizes how each of those points vary between the individuals. It then summarizes all of the different ways that the fishes vary.”
This summary then allows researchers to parse out which variables are the most important or to find patterns in the data.
Other techniques such as Bayesian clustering also help confirm the identities of each fish into ecomorph groups.
Lake Charr are one of the dominant offshore apex predators in the Great Lakes and they are primarily visual predators. So, in addition to the morphological analysis, Moran’s research team is taking their identification a step further and utilizing the individual fish’s visual sensory system, specifically, the photoreceptors within the retinas, to differ between morphs. In order to analyze the photoreceptors, Moran is using overall retinal immunohistology, performed through a collaboration with Dr. Patrick Kerstein and his lab in the Purdue School of Health Sciences.
“Basically, we are looking at the retinas and seeing how the photoreceptors differ between individuals of the same ecomorph category,” Moran said. “Eyes are typically highly conserved traits that don’t vary a lot between individuals. So, when we look at their eyes, any differences that we see are going to be really important and give us an idea of why these different individuals are different. One of the hypotheses is that these morphs are essentially in the early stages of speciation.
“In other systems, the divergence of the visual sensory system was one of the main drivers of speciation. In particular, in the African Rift Lakes when different cichlid species eyes started to diverge, that is believed to be one of the things that led to huge amount of species level diversity. We are using the eyes to understand why these Lake Charr morphs are different and then we can maybe compare it to those African Rift Lakes cichlids and see if potentially these morphs are along that evolutionary pathway to maybe, in hundreds of thousands of years, essentially being their own species.”
Eyes are analyzed in many different ways. Retinas are frozen into embedding molds, which are then sectioned into thin slices which allow them to be analyzed at the cellular level to see the different photoreceptors that exist there.
At this point in his research, Moran is awaiting the data on the retina analysis.
This project also includes genome sequencing from fin clips, which will allow the research team to analyze regions of the genome associated with eye development, specifically the opsin genes which help with the overall development of the eye. That data will offer genetic backing to confirm the phenotyping and ecomorph categorization.
For now, his presentation at the IAGLR conference focused on the morphological side of the work, but the overall project aims to analyze which Lake Charr ecomorphs exist at Klondike Reef and how they differ.
“Overall, we hope to understand the ecomorphological system that exists at Klondike Reef and see if it is the same as what has been observed elsewhere in the Great Lakes,” Moran explained. “If we can understand how these morphs differ, that will help us if we are planning on stocking them into the lower Great Lakes or other systems. We have an idea of what these different morphs are doing, but it is still unclear exactly the ways in which they differ. My side of the project is understanding the functional differences between these morphs.”
This information on the variations in ecomorphs could be important in helping develop a more natural and well-rounded portfolio of Lake Charr populations across the Great Lakes, which in turn could improve stability of the populations and their resilience to potential stressors. Restoring diversity may decrease the likelihood of collapse of Lake Charr populations, such as collapses those that occurred during the early to mid-twentieth century, which extirpated populations of Lake Trout throughout the Great Lakes system, except for in Lake Superior.
“The purpose of the overall grant is to describe and understand the diversity of lake trout on Klondike reef to
support potential eventual broodstock selection for hatcheries,” Euclide explained. “Klondike is offshore and has a different and not well studied population of lake trout and therefore may be a source of fish with different ecology than what is normally stocked into the Great Lakes. So as the U.S. Fish and Wildlife Service looks to continue to restore lake trout, they want to know where they can find fish of different “types” and how to tell them apart (which is hard), so that they can confidently develop brood stocks of the right kinds of lake trout. This is where morphology meets genetics. The ultimate hope is that we can find some genetic markers that match well with Max’s morphology so that we could run a genetic test to ID morphs.”
Thus far, Moran and the research team’s work shows promising results. While additional research still needs to be completed, there is compelling evidence to suggest the existence of a fifth ecomorph at Klondike Reef.
“When we went out sampling, we expected to see the four main previously-described morphs,” Moran shared. “Those are the only ones that studies have indicated exist, but there have always been anecdotal accounts of different morphs in other parts of the lake that haven’t been studied yet, including a fifth morph existing at Klondike Reef. We definitely didn’t expect this, but visually at least we saw that there is a very consistently different fifth group. The morphology has provided some support for that to this point, which has been exciting to see. The immunohistology and genetics will help confirm if this group is really a different ecomorph.”
More excitement could be on the horizon when Moran is finally able to delve into the data from the retinal immunohistology he is performing. His research differs from past work, which typically has been the analysis of zebrafish in a lab setting. Immunohistology is typically not performed in a wild or freshwater setting.
“I think this is a really useful tool to be able to differentiate between populations, different subspecies, different ecomorphs,” Moran said. “It is something that just hasn’t been done yet. It could very well not work
or not tell us anything, but if it does work and tell us something, it could be an important finding in the field and provide a really useful way to differentiate groups.”
But, for now, Moran waits for data to confirm his hypotheses, while other members of the research team look at other traits of Lake Charr, analyzing otoliths for aging to stable isotopes in muscle tissue and livers, fatty acids and even gonadal histology.
This research is funded by the Great Lakes Fish and Wildlife Restoration Act. It is a collaborative effort involving researchers from the U.S. Fish and Wildlife Service, the Michigan Department of Natural Resources, the University of Wisconsin-Milwaukee and Indiana School of Public and Environmental Affairs, all working together to better understand this fish, which is important to individuals ranging from indigenous groups to recreational fishermen.
