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Earhart ML, Blanchard TS, Morrison PR, Strowbridge N, Penman RJ, Brauner CJ, Schulte PM, Baker DW. Identification of upper thermal thresholds during development in the endangered Nechako white sturgeon with management implications for a regulated river. CONSERVATION PHYSIOLOGY 2023; 11:coad032. [PMID: 37228298 PMCID: PMC10205467 DOI: 10.1093/conphys/coad032] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/20/2023] [Accepted: 04/27/2023] [Indexed: 05/27/2023]
Abstract
Climate change-induced warming effects are already evident in river ecosystems, and projected increases in temperature will continue to amplify stress on fish communities. In addition, many rivers globally are impacted by dams, which have many negative effects on fishes by altering flow, blocking fish passage, and changing sediment composition. However, in some systems, dams present an opportunity to manage river temperature through regulated releases of cooler water. For example, there is a government mandate for Kenney dam operators in the Nechako river, British Columbia, Canada, to maintain river temperature <20°C in July and August to protect migrating sockeye salmon (Oncorhynchus nerka). However, there is another endangered fish species inhabiting the same river, Nechako white sturgeon (Acipenser transmontanus), and it is unclear if these current temperature regulations, or timing of the regulations, are suitable for spawning and developing sturgeon. In this study, we aimed to identify upper thermal thresholds in white sturgeon embryos and larvae to investigate if exposure to current river temperatures are playing a role in recruitment failure. We incubated embryos and yolk-sac larvae in three environmentally relevant temperatures (14, 18 and 21°C) throughout development to identify thermal thresholds across different levels of biological organization. Our results demonstrate upper thermal thresholds at 21°C across physiological measurements in embryo and yolk-sac larvae white sturgeon. Before hatch, both embryo survival and metabolic rate were reduced at 21°C. After hatch, sublethal consequences continued at 21°C because larval sturgeon had decreased thermal plasticity and a dampened transcriptional response during development. In recent years, the Nechako river has reached 21°C by the end of June, and at this temperature, a decrease in sturgeon performance is evident in most of the traits measured. As such, the thermal thresholds identified here suggest current temperature regulations may not be suitable for developing white sturgeon and future recruitment.
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Affiliation(s)
- Madison L Earhart
- Corresponding author: Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada. . Tel.: 204-799-9338
| | - Tessa S Blanchard
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada
| | - Phillip R Morrison
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada
- Department of Resource Management and Protection, and Biology Department, Vancouver Island University, 900 Fifth Street Nanaimo, BC V9R 5S5, Canada
| | - Nicholas Strowbridge
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada
- School of Biodiversity, One Health, & Veterinary Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, 464 Bearsden Rd, Bearsden, Glasgow G61 1QH, UK
| | - Rachael J Penman
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada
- Instreams fisheries research, 2323 Boundary Rd Unit 115, Vancouver, BC V5M 4V8, Canada
| | - Colin J Brauner
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada
| | - Patricia M Schulte
- Department of Zoology, University of British Columbia, 6270 University Blvd. Vancouver, BC V6T 1Z4, Canada
| | - Daniel W Baker
- Department of Fisheries and Aquaculture, Vancouver Island University, 900 Fifth Street, Nanaimo, BC V9R 5S5, Canada
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O’Sullivan AM, Corey EM, Collet EN, Helminen J, Curry RA, MacIntyre C, Linnansaari T. Timing and frequency of high temperature events bend the onset of behavioural thermoregulation in Atlantic salmon ( Salmo salar). CONSERVATION PHYSIOLOGY 2023; 11:coac079. [PMID: 36685329 PMCID: PMC9845963 DOI: 10.1093/conphys/coac079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 11/25/2022] [Accepted: 12/22/2022] [Indexed: 06/17/2023]
Abstract
The role of temperature on biological activities and the correspondent exponential relationship with temperature has been known for over a century. However, lacking to date is knowledge relating to (a) the recovery of ectotherms subjected to extreme temperatures in the wild, and (b) the effects repeated extreme temperatures have on the temperatures that induce behavioural thermoregulation (aggregations). We examined these questions by testing the hypothesis that thermal thresholds which initiate aggregations in juvenile Atlantic salmon (AS) (Salmo salar) are not static, but are temporally dynamic across a summer and follow a hysteresis loop. To test our hypothesis, we deployed custom-made underwater camera (UWC) systems in known AS thermal refuges to observe the timing of aggregation events in a natural system and used these data to develop and test models that predict the temperatures that induce thermal aggregations. Consistent with our hypothesis our UWC observations revealed a range of aggregation onset temperatures (AOT) ranging from 24.2°C to 27.1°C, thus confirming our hypothesis that AOTs are dynamic across summer. Our models suggest it take ~ 11 days of non-thermally taxing temperatures for the AOT to rebound in the study river. Conversely, we found that as the frequency of events increased, the AOT declined, from 27.1°C to 24.2°C. Integrating both model components led to more robust model performance. Further, when these models were tested against an independent data set from the same river, the results remained robust. Our findings illustrate the complexity underlying behavioural thermoregulation in AS-a complexity that most likely extends to other salmonids. The frequency of extreme heat events is predicted to increase, and this has the capacity to decrease AOT thresholds in AS, ultimately reducing their resilience to extreme temperature events.
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Affiliation(s)
- Antóin M O’Sullivan
- Corresponding author: FOREM, University of New Brunswick, Fredericton, Fredericton, New Brunswick, NB E3B 5A3, Canada
| | - Emily M Corey
- Canadian Rivers Institute, University of New Brunswick, New Brunswick, NB E3B 5A3, Canada
- Biology, University of New Brunswick, Fredericton, Canada
| | - Elise N Collet
- FOREM, University of New Brunswick, Fredericton, Fredericton, New Brunswick, NB E3B 5A3, Canada
- Canadian Rivers Institute, University of New Brunswick, New Brunswick, NB E3B 5A3, Canada
| | - Jani Helminen
- Natural Resources InstituteFinland, Helsinki, Uusimaa, 00790, Finland
| | - R Allen Curry
- FOREM, University of New Brunswick, Fredericton, Fredericton, New Brunswick, NB E3B 5A3, Canada
- Canadian Rivers Institute, University of New Brunswick, New Brunswick, NB E3B 5A3, Canada
- Biology, University of New Brunswick, Fredericton, Canada
| | - Chris MacIntyre
- FOREM, University of New Brunswick, Fredericton, Fredericton, New Brunswick, NB E3B 5A3, Canada
| | - Tommi Linnansaari
- FOREM, University of New Brunswick, Fredericton, Fredericton, New Brunswick, NB E3B 5A3, Canada
- Canadian Rivers Institute, University of New Brunswick, New Brunswick, NB E3B 5A3, Canada
- Biology, University of New Brunswick, Fredericton, Canada
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