Lahontan Trout
From the time I was a little girl, I was always different. While other parents were successfully dressing their daughters for school in adorable ruffles and smocked dresses, my parents were wrestling me out of Dad’s fishing waders and rubber boots just long enough to go to school. I was a girl acting in a uniquely creative, vehemently independent, and bracingly inquisitive manner. I regularly challenged my parents as I wandered the creeks behind our home in search of exciting adventures and new investigations. To my benefit, my parents always embraced this curiosity and creativity, encouraging me to explore my favorite environment.
I always wanted to be a fish, living and breathing underwater, shooting the rapids to feast on a morning hatch, and exploring the mysteries that remain so elusive to us land dwellers. My journey began in the mountains of North Georgia where Dad taught me to cast a fly rod in the front yard, trying to “catch” our playful black labs and grey tabbies using small toys tied to the end of fly line. I practiced on the lakes and streams of the Blue Ridge Mountains and the ever-changing tides of St. Simons Island. At age 8, my Mom nervously put this “I can do it” girl on a plane to fly solo across the country to join my Dad and his brothers on their annual fly fishing trip to Montana, (an experience I prized as my first real fishing trip). I was always a fish at heart, wishing I could swim amongst the bull and redband trout we caught.
And here I am, an adult, with my personality and drive essentially unchanged. Still the inquisitive investigator, I am lucky enough to have embraced my passion, working toward a career that seems too good to be true, all in a location I consider heaven on earth. I am a doctoral student at the University of Nevada, Reno, working alongside my influential and encouraging mentors, Tom Parchman and Mary Peacock, in the Ecology, Evolution, and Conservation Biology program as I investigate conservation genetics and genomics of trout of the Lake Tahoe Basin.
The Washoe Tribe originally inhabited the Lake Tahoe Basin, prizing the only native salmonid, the Lahontan cutthroat trout, as a staple in both their heritage and their diets. In the mid 1800s, settlers explored the area, eventually introducing a slew of non-native salmonids including Mackinaws, rainbows, brooks, browns, and kokanees. Due to water diversions, overharvesting, and the introduction of non-native salmonids, Lahontan cutthroat populations severely declined, and the species eventually disappeared from the basin in the 1940s.
Since that time, researchers have been working cooperatively with private, state and federal agencies to reintroduce Lahontan cutthroats to a large portion of their native habitat. A significant threat to Lahontan cutthroat survival, however, lurks in the streams leading into Lake Tahoe. Rainbow trout are a close congener of cutthroat trout and readily hybridize with them. The hybrid dynamic is such that over multiple generations, the cutthroat trout genome is completely lost. In other words; rainbows and cutthroats are capable of interbreeding, resulting in cutbow offspring, or “mutts” in which genetically pure individuals are lost. Over time and through several generations, the hybrids of the Tahoe Basin outnumbered pure Lahontan cutthroats, resulting in the local extinction of the subspecies.
Reintroduction efforts of Lahontan cutthroats in Fallen Leaf Lake, (an upstream source of water) have been largely unsuccessful due to the thriving, naturalized population of rainbows. My research aims to characterize population demographic and genetic structure of rainbow trout found in tributaries leading into Lake Tahoe in an effort to understand movement within and among subpopulations. The Lake Tahoe Basin is the site of an intensive research effort by state and federal game and fish agencies to develop strategies for the reintroduction of the, (Endangered Species Act listed) native Lahontan cutthroat trout into its historical lake habitat. I hope to inform management agencies on the most effective strategies for reintroducing the basin’s only native salmonid.
This past summer, with the help my invaluable field crew, I traversed the Tahoe Basin, successfully collecting several hundred tiny, 2 mm fin clips from naturalized rainbows which we then released. I have extracted DNA, and I am using a state of the art genotype-by-sequencing approach to quantify the genetic structure of these naturalized rainbows at a very fine scale, (far more resolved than traditional conservation genetics approaches allow). Sequencing random sections of the genome allows us to identify single nucleotide polymorphisms, or SNPs, (“snips”) in individuals of different subpopulations.
As the name suggests, these polymorphisms represent a difference of a single base pair in otherwise identical strands of DNA from different individuals. Using this method, we are capable of identifying hundreds of thousands of SNPs, allowing us to characterize individuals of geographically different regions and potentially isolated subpopulations. In this way, for example, we can determine genetic differences between trout of the North Shore versus those of the West Shore.
Estimates of gene flow will provide information on the extent of movement among tributaries and inform mitigation efforts to prevent re-colonization of streams by non-native salmonids. We will be able to infer movement between and among subpopulations, identifying subpopulations that live a resident lifestyle versus a migratory one. These analyses will then be used to develop a management strategy to reduce or eliminate the threat of hybridization as reintroduction of the native Lahontan cutthroat trout in this basin progresses.
This research represents a significant step in understanding the success of naturalized non-native salmonids in the Lake Tahoe Basin, informing conservation efforts for the reintroduction and preservation of our native species. In this way, I am working to restore, protect, and preserve our native fishes while increasing community awareness of the beautiful natural ecosystems in which we live.
