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Lonthair JK, Wegner NC, Cheng BS, Fangue NA, O'Donnell MJ, Regish AM, Swenson JD, Argueta E, McCormick SD, Letcher BH, Komoroske LM. The gill oxygen limitation hypothesis remains unsupported by experimental evidence. Response to 'Testing mechanistic theories must be based on correct interpretations'. J Exp Biol 2024; 227:jeb248173. [PMID: 39193665 DOI: 10.1242/jeb.248173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Accepted: 07/18/2024] [Indexed: 08/29/2024]
Affiliation(s)
- Joshua K Lonthair
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- National Research Council under contract to Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037-1508, USA
| | - Nicholas C Wegner
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla 92037-1508, CA, USA
| | - Brian S Cheng
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Nann A Fangue
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA 95616, USA
| | - Matthew J O'Donnell
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Amy M Regish
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - John D Swenson
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Estefany Argueta
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Stephen D McCormick
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Benjamin H Letcher
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Lisa M Komoroske
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
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Waller MJ, Humphries NE, Womersley FC, Loveridge A, Jeffries AL, Watanabe Y, Payne N, Semmens J, Queiroz N, Southall EJ, Sims DW. The vulnerability of sharks, skates, and rays to ocean deoxygenation: Physiological mechanisms, behavioral responses, and ecological impacts. JOURNAL OF FISH BIOLOGY 2024; 105:482-511. [PMID: 38852616 DOI: 10.1111/jfb.15830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 05/08/2024] [Accepted: 05/20/2024] [Indexed: 06/11/2024]
Abstract
Levels of dissolved oxygen in open ocean and coastal waters are decreasing (ocean deoxygenation), with poorly understood effects on marine megafauna. All of the more than 1000 species of elasmobranchs (sharks, skates, and rays) are obligate water breathers, with a variety of life-history strategies and oxygen requirements. This review demonstrates that although many elasmobranchs typically avoid hypoxic water, they also appear capable of withstanding mild to moderate hypoxia with changes in activity, ventilatory responses, alterations to circulatory and hematological parameters, and morphological alterations to gill structures. However, such strategies may be insufficient to withstand severe, progressive, or prolonged hypoxia or anoxia where anaerobic metabolic pathways may be used for limited periods. As water temperatures increase with climate warming, ectothermic elasmobranchs will exhibit elevated metabolic rates and are likely to be less able to tolerate the effects of even mild hypoxia associated with deoxygenation. As a result, sustained hypoxic conditions in warmer coastal or surface-pelagic waters are likely to lead to shifts in elasmobranch distributions. Mass mortalities of elasmobranchs linked directly to deoxygenation have only rarely been observed but are likely underreported. One key concern is how reductions in habitat volume as a result of expanding hypoxia resulting from deoxygenation will influence interactions between elasmobranchs and industrial fisheries. Catch per unit of effort of threatened pelagic sharks by longline fisheries, for instance, has been shown to be higher above oxygen minimum zones compared to adjacent, normoxic regions, and attributed to vertical habitat compression of sharks overlapping with increased fishing effort. How a compound stressor such as marine heatwaves alters vulnerability to deoxygenation remains an open question. With over a third of elasmobranch species listed as endangered, a priority for conservation and management now lies in understanding and mitigating ocean deoxygenation effects in addition to population declines already occurring from overfishing.
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Affiliation(s)
- Matt J Waller
- Marine Biological Association, The Laboratory, Plymouth, UK
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
| | | | | | | | - Amy L Jeffries
- Marine Biological Association, The Laboratory, Plymouth, UK
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
| | - Yuuki Watanabe
- Research Center for Integrative Evolutionary Science, The Graduate University for Advanced Studies, SOKENDAI, Kanagawa, Japan
| | - Nicholas Payne
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Jayson Semmens
- Institue for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
| | - Nuno Queiroz
- CIBIO/InBIO, Universidade do Porto, Vairão, Portugal
- BIOPOLIS, Program in Genomics, Biodiversity and Land Planning, CIBIO, Vairão, Portugal
| | | | - David W Sims
- Marine Biological Association, The Laboratory, Plymouth, UK
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
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Lonthair JK, Wegner NC, Cheng BS, Fangue NA, O'Donnell MJ, Regish AM, Swenson JD, Argueta E, McCormick SD, Letcher BH, Komoroske LM. Smaller body size under warming is not due to gill-oxygen limitation in a cold-water salmonid. J Exp Biol 2024; 227:jeb246477. [PMID: 38380449 PMCID: PMC11093110 DOI: 10.1242/jeb.246477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 01/10/2024] [Indexed: 02/22/2024]
Abstract
Declining body size in fishes and other aquatic ectotherms associated with anthropogenic climate warming has significant implications for future fisheries yields, stock assessments and aquatic ecosystem stability. One proposed mechanism seeking to explain such body-size reductions, known as the gill oxygen limitation (GOL) hypothesis, has recently been used to model future impacts of climate warming on fisheries but has not been robustly empirically tested. We used brook trout (Salvelinus fontinalis), a fast-growing, cold-water salmonid species of broad economic, conservation and ecological value, to examine the GOL hypothesis in a long-term experiment quantifying effects of temperature on growth, resting metabolic rate (RMR), maximum metabolic rate (MMR) and gill surface area (GSA). Despite significantly reduced growth and body size at an elevated temperature, allometric slopes of GSA were not significantly different than 1.0 and were above those for RMR and MMR at both temperature treatments (15°C and 20°C), contrary to GOL expectations. We also found that the effect of temperature on RMR was time-dependent, contradicting the prediction that heightened temperatures increase metabolic rates and reinforcing the importance of longer-term exposures (e.g. >6 months) to fully understand the influence of acclimation on temperature-metabolic rate relationships. Our results indicate that although oxygen limitation may be important in some aspects of temperature-body size relationships and constraints on metabolic supply may contribute to reduced growth in some cases, it is unlikely that GOL is a universal mechanism explaining temperature-body size relationships in aquatic ectotherms. We suggest future research focus on alternative mechanisms underlying temperature-body size relationships, and that projections of climate change impacts on fisheries yields using models based on GOL assumptions be interpreted with caution.
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Affiliation(s)
- Joshua K. Lonthair
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- National Research Council under contract to Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037-1508, USA
| | - Nicholas C. Wegner
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla 92037-1508, CA, USA
| | - Brian S. Cheng
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Nann A. Fangue
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA 95616, USA
| | - Matthew J. O'Donnell
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Amy M. Regish
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - John D. Swenson
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Estefany Argueta
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Stephen D. McCormick
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Benjamin H. Letcher
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Lisa M. Komoroske
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
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