Climate-related stressors and their effects on sablefish (Anoplopoma fimbria) cardiorespiratory physiology and immunology

Leeuwis, Robine Helena Jannigje (2023) Climate-related stressors and their effects on sablefish (Anoplopoma fimbria) cardiorespiratory physiology and immunology. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Fish in aquatic environments worldwide are increasingly experiencing extreme abiotic conditions, including high temperatures and hypoxia, due to global warming and eutrophication related to anthropogenic activities. However, our understanding of how these climate-related stressors impact fish physiology is often limited, and many critical questions in this area of ecophysiology research remain unanswered. In this dissertation, I have addressed several knowledge gaps related to fish (teleost) cardiorespiratory physiology and immunology, using the sablefish (Anoplopoma fimbria) as a model species. The sablefish is an economically and ecologically important species in the North Pacific, and an emerging aquaculture species, and it has a unique life history as it encounters a wide range of temperatures and O₂ levels in the wild. My research shows that sablefish, as compared to Atlantic salmon (Salmo salar), are only slightly less tolerant of acute exposure to high temperatures (critical thermal maximum ~25°C), but much more tolerant of acute hypoxia (O₂ level at loss of equilibrium ~5% air sat.). However, I also discovered that acute hypoxia can substantially constrain the cardiorespiratory response and tolerance of sablefish when subsequently exposed to elevated temperatures. This finding has major ecological implications for fishes given that high temperatures and hypoxia often co-occur in the environment. Finally, I found that chronic hypoxia can impair the sablefish’s adaptive immune response (as measured by total IgM antibody titers) to antigens of the pathogen Aeromonas salmonicida, a bacteria that frequently causes disease (furunculosis) in various aquaculture fish species. On the other hand, chronic hypoxia only had a limited effect on the innate immune response. Thus, this research highlights that distinct branches of the fish immune system can respond differently to hypoxia. Overall, this thesis provides key ecophysiological data on the sablefish, and greatly improves our fundamental knowledge of the impact of environmental stressors on fishes. In addition, these results help us to understand, and predict, the consequences of climate change on fish species with importance to fisheries, aquaculture, and conservation efforts.

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