This summer I was part of an international-interdisciplinary team studying a social-ecological system in the Selenge River Valley of northern Mongolia. I know: that’s two hyphens too many, but hang in there, there were also the largest salmon in the world, sheep as far as the eye could see, and crispy yogurt chips. There were also a lot of people –a huge team that included conservation biologists, professors, graduate students, and undergraduates (and even some researchers’ babies who, I might add, are the finest morale boosters!). As part of the Mongolian American Aquatic Ecology Initiative (MAERI), we were trying to understand how the upcoming building of a hydroelectric dam would affect the local ecosystem, and thus the people and animals that use the river on a daily basis. That’s a huge undertaking. My research, which focused how a dam might affect the behavior of native fish, was one tiny slice. That being said, I could not have done my research without help from every single person on our team.
Dams bring change. They alter river flow and change the physical landscape around them, flooding lands and displacing people living near them. Even before they modify water patterns, their production brings people and the building of roads to transport materials to the construction site. Last but not least, a dam is a pretty big structure in the middle of a stream. That’s certainly new, especially to the animals that have been living in these rivers all their lives.
So how might this affect fish? Well, changing how water flows affects where fish are able to live and swim. Construction often brings noise disruption and chemical pollution to the river. Lastly, the dam itself presents a potentially uncrossable barrier, which could prevent fish from accessing their full range. Many dams include passageways for fish to swim through, but little is known about which species are able to use these passages. In fact, many fish might not use passages at all .
Previous research coming out of the MAERI team focused on whether certain salmon species in these rivers are able to swim at the speeds necessary to use these passages . As a behavioral ecologist, I had a simple corollary question. Even if the fish were able to swim in these passages, would they even try? If a giant alien spaceship landed in the middle of your street, right in front of your driveway, would you try to drive through it? How about if there was a tunnel with bright red arrows pointing toward it, like some cartoon carnival ride indicating “fun underpass ahead”?
If you said yes, than you are bolder than I! And I’d expect that some people would be with me, hiding in our homes while clutching our dogs and waiting to see what happens. Others might hop in their cars and try to go to work the next day. Some might wait just a few days, while others may never venture out. This variation in responses is because of our diverse personalities: different levels of boldness or willingness to take risks. Similar phenomena might be happening with the fish in these rivers, and really all fish species around the world. Scientists are repeatedly finding that some fish are bold, willing to take great risks for rewards, and this has consequences for many aspects of their lives (e.g., [3,4]). Other fish are shy and others are in between. So my research question became not only would fish try, but which fish would try? Which proportion of the fish population might try to cross a dam and what kind of personalities would they have? Would they be big fish or small fish? Perhaps hungry fish might be more likely to take a risk and cross the dam compared to well-fed ones. I, for example, might be willing to brave the alien space ship for another one of the wild strawberries I ate while hiking in Mongolia.
Unfortunately, to answer these questions I could not send out a survey asking fish their feelings on the matter. Instead, I went to the field to make observations about their behavior. I built large arenas out of collapsible kiddie pools (not kidding, I had to lug those suckers halfway around the world) and created a fake “dam” within my areas with a small hole in the middle. We set those arenas right next to the river and filled them with river water. In fact, we initially set one pool a little too close to the river, such that the river flooded it after a large storm. I will chalk that up to a learning experience, albeit an extremely humbling one. We soon perfected our skills in swiftly moving kiddie pools and water. Extra hands and water pumps made all the difference.
After properly placing my kiddie pool arenas, my amazing teammates went fishing for our study participants, who we placed in these arenas. We then video recorded each fish, seeing how it responded to the barrier. We also collected other information on these fish: how bold they were in an open arena, the fishing equipment use to catch them, and their length and weight. We hoped by taking these measurements in semi-natural conditions (same climate, same water, 24 hours after they were caught), we would be able to get an accurate snap shot of who these fish were and how they might respond to a barrier.
I have no answers as of yet. My incredibly hard-working undergraduate collaborators and I are still watching the videos from this summer, extracting the relevant information about each fish’s behavior (such as how long it took for them to cross the barrier, how many times they crossed). It will take months to properly watch all the videos and run the analysis. Scoring videos is not nearly as glamorous as actually being in Mongolia, placing fish in large kiddie pools with a cartoon pirate theme on the outside. But, every time I watch a video I am reminded of the beauty of these rivers and what a privilege it was to have done research there.
Lea Pollack is a fourth year graduate student in the Graduate Group in Ecology at UC Davis. You can learn more about her research at her website. Her research in Mongolia was funded by an NSF International Research Experiences for Students grant. For more information about the research done by the MAERI team, visit their website.
 Brown, J. J., Limburg, K. E., Waldman, J. R., Stephenson, K., Glenn, E. P., Juanes, F., & Jordaan, A. (2013). Fish and hydropower on the U.S. Atlantic coast: failed fisheries policies from half-way technologies. Conservation Letters, 6(4), 280-286. doi:10.1111/conl.12000
 Hartman, K.J., & Jensen, O. (2016). Anticipating climate change impacts on Mongolian salmonids: Bioenergetics models for lenok and Baikal grayling. Ecology of Freshwater Fish, 26(3), 383-396.
 Biro, P. A., & Post, J. R. (2008). Rapid depletion of genotypes with fast growth and bold personality traits from harvested fish populations. Proceedings of the National Academy of Sciences, 105(8), 2919-2922.
 Cooke, S. J., Suski, C. D., Ostrand, K. G., Wahl, D. H., & Philipp, D. P. (2007). Physiological and behavioral consequences of long-term artificial selection for vulnerability to recreational angling in a teleost fish. Physiol Biochem Zool, 80(5), 480-490. doi:10.1086/520618