Aquaculture industry resilience against climate change : examining the effects of mild stress on heat tolerance in juvenile Chinook salmon (Oncorhynchus tshawytscha).

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Biological Sciences
Degree name
Master of Science
Publisher
Journal Title
Journal ISSN
Volume Title
Language
English
Date
2022
Authors
Gilbertson, Caroline
Abstract

Climate change is already affecting aquaculture around the world and impacts are projected to worsen in many areas. Both Australia and New Zealand (NZ) have experienced multiple record-breaking heatwaves that have resulted in disease and mortality events in various aquaculture sectors. This thesis aimed to investigate cross-tolerance as a potential mechanism for increasing tolerance to heat stress in Chinook salmon (Oncorhynchus tshawytscha), a significant aquaculture species in NZ that may be impacted by climate change induced warming and weather events. Cross-tolerance describes a phenomenon where organism exposure to one stressor triggers a physiological stress response which confers increased resilience to a second subsequent stressor. Cross-tolerance has been observed in multiple teleosts, but in Chinook salmon has only been investigated in a single study on pre-swim life stages. In order to investigate the potential for cross-tolerance, two priming stressors, crowding (Chapter 2) and hypoxia (Chapter 3), were investigated in separate experiments on Chinook salmon smolts.

Crowding (20-min at ~47.8 kg / m-3 density) had no effect on Chinook salmon heat tolerance, measured as critical thermal maximum (CTmax). The lack of effect was attributed to an insufficient crowding stressor severity. Moderate hypoxia stress priming (40% oxygen saturation for 2 h) resulted in cross- susceptibility to heat stress, which describes where stressor priming results in worsened tolerance to a second subsequent stressor. The physiological mechanisms by which cross-susceptibility occurs are largely unknown. Lastly, a survey investigating the climate change perceptions of Australian and NZ aquaculture industry members was completed to inform and support the cross-tolerance experiments and future research (Chapter 4). Industry members were asked which aspects of climate change were of most concern to their jobs and industry sectors, what they wanted from climate change research, and whether they would be willing to implement resilience tools, like cross-tolerance induction. Research investigating the perceptions of Australasian aquaculture industries on climate change threats has been lacking. Responses indicated that the Australian and NZ aquaculture industries are greatly concerned about the current and potential impacts of climate change. However, resilience tools with a growth trade-off had less likelihood of implementation. This thesis contributes novel insights into the potential for cross-tolerance solutions for increasing aquaculture species resilience to climate change threats.

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Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
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