research

Graduate research

My current research focuses on the salmonid species Oncorhynchus mykiss, also known as steelhead and rainbow trout. Rainbow trout and steelhead can hatch from the same clutches of eggs in freshwater streams, but only steelhead grow up to migrate to the ocean and back. Rainbow trout remain in freshwater for the entire lives. The offspring of both steelhead and rainbow trout can either remain resident rainbow trout, or undergo the physiological and morphological changes known as “smoltification” to become migrant steelhead trout. Smoltification allows steelhead to transition from inhabiting a freshwater habitat, to surviving in a marine habitat. What exactly determines if an individual smolts is difficult to discern because it results from a combination of many variables related to genetics, environmental factors, and an individual’s body condition. My research as a graduate student specifically explores neutral and adaptive genetic relationships of the O. mykiss populations and their influences on O. mykiss migration strategies. Adaptive genetic variation that I included in my graduate research was a specific chromosomal inversion on chromosome Omy05 that impacts migration strategy in O. mykiss (resident vs. migrant) and locus GREB1L which affects run timing, or when an individual initiates their return to their natal freshwater stream. My dissertation examined neutral and adaptive genetic relationships of the O. mykiss populations from the California’s Central Valley.

My first chapter investigated patterns of population genetics and distribution of adaptive genetic variation in the four Central Valley steelhead hatchery populations from 2011—2019. Hatcheries fin clip each returning steelhead to sample for genetics. Genotyping each returning steelhead over multiple years allows us to reconstruct a pedigree from each individual’s genetic information by identifying their parents. Additionally, we genotyped for Omy05 to consider adaptive genetic variation and predicted migratory strategy (resident vs. migrant). We found that the use of steelhead from a coastal population in one of these hatchery programs, not one from the Central Valley, imparted significant genetic and phenotypic differences from the other hatchery programs.

My second chapter presented a case study in a O. mykiss populations from the segmented Napa Valley watershed of Putah Creek, California, which is located between the central coastal and Central Valley. Putah Creek was segmented by the construction of dams and formation of large reservoir Lake Berryessa in the 1950s. Additionally, hatchery trout have been repeatedly stocked in Putah Creek throughout the years. To determine the genetic composition of the O. mykiss populations of Putah Creek, O. mykiss were caught via fly fishing in the streams above and below Monticello Dam, fin clipped, and genotyped with both neutral and adaptive genetic markers for comparison with 40 reference populations. We genotyped for both Omy05 to consider predicted resident and migrant strategies, and GREB1L for seasonal run timing. There were distinct genetic and phenotypic patterns above and below impassable Monticello Dam, with O. mykiss below this barrier resembling Central Valley and hatchery stocking populations and those above possessing coastal ancestry. We also found that populations below Monticello Dam had a different distribution of adaptive genetic variation compared to those above.

My third chapter analyzed the strength of association between GREB1L genotype and run timing phenotype in O. mykiss sampled from the Sacaramento River. Our results build on my previous chapters that find O. mykiss with Central Valley lineage have decreased association between adaptive genetic variation and genotype compared to O. mykiss from central coast populations.

undergraduate research

As an undergraduate, I was a research assistant for Dr. Bill Detrich at Northeastern University’s Marine Science Center. Our work focused on Antarctic fish, including the icefish family. Icefish have undergone a series of unique adaptations, including the loss of red blood cells. Icefish blood is instead a milky color. The Detrich lab uses Antarctic fish as a study system for understanding adaptation at the molecular scale. During my three years working for this lab, I was deployed to Palmer Station for the 2016 Winter (May – October) to rear embryos for developmental studies and to sample adult fish for different gene expression studies.