UC Santa Cruz

The biodiversity of terrestrial and aquatic communities is driven by the ability of species to successfully disperse to and persist in different habitats. For many marine fishes, dispersal occurs via a planktonic larval form that resides in the surface layer of the ocean for a period of days to months before moving to juvenile habitats and metamorphosing. The period from hatching to soon after settlement is a critical period for fish, as it features high mortality rates. In this dissertation, I investigate selective factors that influence larval dispersal, biogeography, and population persistence in the Eastern Pacific. In Chapter 1, I examined whether morphology of larval eels (order Anguilliformes) can predict larval geographic range, and found that morphological traits of intermediate-stage larvae predicted larval latitudinal range, as leptocephali with larger relative predorsal lengths and snout-to-anus lengths exhibited larger larval ranges. In Chapter 2, I used RAD sequencing to examine genetic structure of California morays (Gymnothorax mordax) and found that California morays exhibit local adaptation in the face of high gene flow, with selection likely taking place primarily during the late larval or early juvenile period. In Chapter 3, I used highly quantitative methods to test if skin coloration of California morays around Catalina Island, CA were correlated with their habitats. I found that eels were yellower and lighter in sandy habitats and that countershading (surprising for a benthic, crevice-dwelling fish) was present on the head and tail. We hypothesize that selection on coloration is also occurring during the first few years after settlement. In Chapter 1, I used a long-term west coast ichthyoplankton dataset to examine what environmental factors are influencing larval distributions of five commercially-important taxa of fishes, as well as larval fish overall: Pacific sanddab (Citharichthys sordidus), California sheephead (Semicossyphus pulcher), cabezon (Scorpaenichthys marmoratus), rockfishes (Sebastes spp.) and sablefish (Anoplopoma fimbria). I found that Bayesian hierarchical modeling is an effect method to model larval fish abundance, and that sea surface height was the strongest environmental covariate.