ORCID ID

https://orcid.org/0000-0002-8180-3360

Date Awarded

2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

Eric J Hilton

Committee Member

Jan R McDowell

Committee Member

Michael Vecchione

Committee Member

Christopher D Jones

Abstract

The Antarctic fish fauna is unique, with approximately 88% of the ~375 known species endemic to the Southern Ocean. One group, the perciform suborder Notothenioidei, dominates fish richness and biomass. These fishes possess several traits that allow existence in frigid conditions, but also limit their ability to cope with temperature increases due to climate change. In the western Antarctic Peninsula (WAP) region, a combination of anthropogenic impacts, including climate change and fishing pressure, threaten these fishes. The WAP is one of the most rapidly warming regions globally (3.4 °C per century) and has the highest fishing pressure for Antarctic krill in the Southern Ocean, which can result in the bycatch of larval nototheniods. The goal of my dissertation is to utilize interdisciplinary techniques to better understand the diversity of these unique fishes, as well as more accurately predict how their early life stages will respond to future conditions. Data in my dissertation are sourced from the Palmer Antarctica Long-Term Ecological Research (Palmer LTER) program, established in 1990 to study the pelagic ecosystem of the WAP. Larval fishes are captured annually as bycatch in Palmer LTER zooplankton net tows and represent the longest running (30+ years), fisheries-independent time series of Antarctic fishes. In Chapter 2, I utilize this novel time series to model the impacts of environmental change on Pleuragramma antarctica (Nototheniidae) larvae. Adult P. antarctica use sea ice as spawning habitat and are important prey for penguins and other predators. I show that warmer sea surface temperature and decreased sea ice are associated with reduced larval abundance, indicating these keystone fish could disappear regionally in the near future. In Chapter 3, I employ a combination of morphological and genetic analyses to describe unknown early life stages of a rare notothenioid genus (Akarotaxis; Bathydraconidae), which led to the discovery of a new species, Akarotaxis n. sp., that is described in Chapter 4. These two Chapters provide information on the evolution of notothenioids and biology of Akarotaxis n. sp., which appears to be endemic to the WAP region. In Chapter 5, I model biotic and abiotic drivers of phenology and growth of the larval fish assemblage near Palmer Station on the WAP. Several fish species are positively correlated with copepod and diatom abundances, which are modulated by interannual changes in sea ice. In addition, I model dispersion pathways of nototheniid yolk-sac larvae to locate their potential spawning areas. In Chapter 6, I use thermal tolerance experiments to study the physiological vulnerability to warming of larvae from three notothenioid families (Nototheniidae, Channichthyidae, and Artedidraconidae). Thermal tolerance increases with body length in larval channichthyids, suggesting that younger, less motile larvae may be especially susceptible to rapid warming events such as marine heatwaves. Results also indicate that the artedidraconid species Neodraco skottsbergi possesses one of the highest thermal tolerances reported for endemic notothenioids of any life stage. I offer ecological and evolutionary hypotheses that may explain this remarkable tolerance. My research provides multifaceted information on the vulnerable early life stages of fishes in a rapidly changing ecosystem. These insights inform future research priorities and will significantly contribute to the ongoing development of Marine Protected Areas in the Southern Ocean.

DOI

https://dx.doi.org/10.25773/v5-nq6n-y836

Rights

© The Author

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