Master's research
Influence of coastal-origin mesoscale eddies on ichthyoplankton assemblages in the Gulf of Alaska
Ocean conditions can potentially impact fish species with drifting early life history stages. Mesoscale eddies formed along the continental shelf of the Gulf of Alaska (GOA) during winter and spring are large and ubiquitous, facilitating cross-shelf water exchange. These mesoscale eddies may facilitate transport of early larval stages of fish from shelf to slope. I propose to examine the relationship between ichthyoplankton (eggs, larvae, juveniles) and mesoscale eddies propagating along the GOA shelf break. In a multi-faceted approach, I will first examine ichthyoplankton assemblages from three well-characterized eddies (Haida, Sitka, and Yakutat) that were sampled in 2005. I will compare ichthyoplankton indices from within eddy to shelf regions using data from spring 2003. These samples will be analyzed for relative indices of diversity and abundance of eggs, larvae, and juveniles of species within each eddy. Using historical altimetry data (1993 to present), I proposed to reconstruct a time series of eddy presence in the western GOA (particularly in the Kodiak Island to Shelikof Strait region) to characterize annual eddy seasonality, strength, frequency, and persistence in the western GOA. I will then look at correlations between eddy properties (timing, magnitude, frequency, propagation direction) and annual abundance estimates of ichthyoplankton collected over the continental shelf in the same region. Resulting patterns will be modeled to describe the relationship between life history of shelf-spawning species and mesoscale eddy dynamics. Results will help determine whether eddies are a source of larval exchange between the continental shelf and slope, and elucidate mechanisms that could be applicable to other, less well characterized areas such as the Bering Sea.
Previous research
Vertical distribution of Decapoda larvae in response to freshwater in a Chilean fjord
Investigation of vertical zoeal abundance in response to a constant strong pycnocline located between 2 and 4 m in a southern Chilean fjord. Salinity of a superficial water layer capping the fjord varied by 1 to 25 ppt, and temperature by 9 to 17 ºC. Zoeal abundance was compared from above and below this strong pycnocline. Zoeas were further sorted by family group (Anomura: Galatheidae, Porcellanidae, Lithodidae, Paguridae; Brachyura: Cancridae/ Xanthidae/ Majidae, Grapsidae, Pinnotheridae, Belliidae/ Atelecyclidae, Hymenosomidae; Caridea: Hippolytidae/ Campylonotidae/ Pandalidae; Dendrobrachiata: Sergestidae), and into early or late larval stages depending upon presence of pleopodal buds. Zoeal abundance was statistically found to be much higher below the cline (p=0.018). Separate testing of each family group also revealed higher abundance below the cline (p<0.0001). Analysis of early zoea and late zoea abundance below the cline was found to be higher for both larval stages (p<0.0001), while megalopa abundance was not found to be significantly different (p=0.2171). This suggests that the species of Decapoda zoeas sampled preferentially inhabit below this strong pynocline, though responses to physiological constraints or physical density barriers appear to differ between family groups.
Variation in breeding display behavior and evidence of laterality in male harbor seals (Phoca vitulina)
(Undergraduate thesis) During the breeding season male harbor seals (Phoca vitulina) perform complex visual and acoustic displays, such as snorting, flipper-slapping, underwater roars, and tossing objects. While variation in underwater acoustic behavior of this species have been extensively studied, above water behaviors that likely also play an important function in the reproductive success of individuals is poorly understood. In this study, we observed behaviors of male seals in Monterey Bay, California, during the 1994 and 2005 breeding seasons to determine whether individuals varied in their expression of above water breeding season behaviors. We filmed individual male seals, which are distinguished by pelt coloration, and later scored their behaviors using stop-frame video analysis. Individuals displayed a high degree of variation in (1) uniqueness in their choice of behaviors and (2) handedness. However, while males proved to exhibit individuality, we found a high degree of similarity in the behaviors used to initiate each behavioral sequence. Handedness in flipper usage was observed during reproductive displays with individuals consistently using either their right or left flipper (chi-square test: p<0.05). The usage of certain behaviors differed in frequency between individuals (one-sample t-test: p<0.1), and between individuals and the average of all males observed in this study (one-sample t-test: p<0.05) suggesting that there is much variation in courting behaviors. Furthermore, breeding displays were often begun with flipper slaps (64.4% of the time, as opposed to other behaviors which begun displays less than 10%). This provides evidence for a high degree of individuality of behaviors and lateralization in marine mammals. Laterality has implications to the origin and evolution of brain hemisphere specialization in mammals.