Past Research Projects
Hormones in Yelloweye Rockfish Opercula
Teleostei is a subset of bony ray-finned fish that make up the majority of fish species found throughout the world today. Teleost species contain a bony plate structure called an operculum, which covers and protects their gills. Opercula continuously grow in size throughout certain teleost’s lifecycles by laying down incremental bands, or growth increments (GIs), on a yearly basis (1 light + 1 dark band/year). In the past, these banding patterns (Figure 1) have helped biologists age these fish by counting the number of GIs in the operculum. However, my research focused on extracting vital reproductive and stress-related hormone data from these GIs to help determine lifetime trends in reproductive and stress physiology.
Figure 2 showcases a simplified version of the sampling process of a female yelloweye rockfish (Sebastes ruberrimus) operculum. First, we clipped each GI (1 light + 1 dark layer, (a, b)). Second, we cut individual GIs into smaller pieces for steroid hormone extraction (c). Finally, we have the end result of sampling all GIs of a yelloweye rockfish operculum (d).
I had three main goals in my dissertation relating to the analysis of hormone deposition in GIs of a female teleost operculum that I wanted to address. First, I wanted to determine if reproductive and stress-related hormones were deposited in the individual GIs of the long-lived (>100 years old!) and human-targeted species, the yelloweye rockfish. Second, I wanted to develop female reproductive parameters (e.g., age of sexual maturity and spawning frequency) from these lifetime hormone profiles to improve models for catch limits. Finally, I wanted to construct models with multiple environmental variables (e.g., sea surface temperature) to determine how environmental changes affect the reproductive (including reproductive parameters) and stress physiology of these fish.
My dissertation research resulted in two publications relating to hormones in yelloweye rockfish opercula, which can be found in my Publications page!
Trace Element Concentrations in Leopard Seal Whiskers
Leopard seals (Hydrurga leptonyx) are apex predators and have been identified by scientists as a sentinel species of Antarctica. As a result of their predator status, leopard seal health can be a proxy for the overall health of the Antarctic ecosystem.
I measured mercury and other physiologically relevant trace elements along the length of leopard seal whiskers for my final dissertation chapter. Leopard seal whiskers grow continuously for up to one year, at which time their whiskers are shed during an annual molting season. As a result, their whiskers serve as an important time capsule by providing important biomarkers of health from the past year of the animal’s life. I also measured paired bulk carbon and nitrogen stable isotope ratios in whisker segments to understand general trends in trophic level and foraging location, as it relates to trace element concentrations. These data will help determine contaminant loads of a sentinel species over multiple years and give insight into the health of the leopard seal and the Antarctic ecosystem.
This final chapter on measuring trace elements and stable isotopes in leopard seal whiskers was published in a peer-reviewed journal and can be found on my Publications page!