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Respiratory quotient and the stoichiometric approach to investigating metabolic energy substrate use in aquatic ectotherms

Wang, S, Carter, CG ORCID: 0000-0001-5210-1282, Fitzgibbon, QP ORCID: 0000-0002-1104-3052 and Smith, GG ORCID: 0000-0002-8677-1230 2020 , 'Respiratory quotient and the stoichiometric approach to investigating metabolic energy substrate use in aquatic ectotherms' , Reviews in Aquaculture , pp. 1-30 , doi: 10.1111/raq.12522.

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The respiratory quotient (RQ) has been used extensively as an index to evaluate metabolic energy expenditure in terrestrial animals including humans. In contrast, RQ use in understanding physiology and nutrition of aquatic ectotherms has been restricted due to technical challenges in measuring total CO2 in water. With technical advances in measuring total CO2 in water, RQ in aquatic ectotherms can be accurately determined and is potentially available as a valuable method. Here, we provide a comprehensive review of studies on RQ and metabolic energy substrate use in aquatic ectotherms. Metabolic energy substrate use is evaluated by a reliable stoichiometric bioenergetic approach, based on measuring RQ and nitrogen quotient (NQ) simultaneously. Stoichiometry provides a non‐destructive and unequivocal way to quantify the instantaneous oxidation of each major energy substrate (protein, lipid or carbohydrate). This review aims to refine knowledge about bioenergetics of aquatic ectotherms under different conditions including nutritional aspects of sustainable aquaculture. Notably, stoichiometry provides a promising approach to optimize feeds and feeding regimes to realize sustainable aquaculture under differing conditions and with differing feed ingredients. It also provides an approach to consider climate change impacts and physiological adaptation mechanisms for survival and development in farmed environments and natural ecosystems. Stoichiometric bioenergetics knowledge in aquatic ectotherms has relevance to commercial impacts in the face of overfishing and food security, and ecological significance in the face of environmental change scenarios. We suggest expanding the use of stoichiometry in future bioenergetic research in emerging aquaculture species.

Item Type: Article
Authors/Creators:Wang, S and Carter, CG and Fitzgibbon, QP and Smith, GG
Keywords: metabolic energy substrate use, natural ecosystem, respiratory quotient, stoichiometric bioenergetic approach, sustainable aquaculture
Journal or Publication Title: Reviews in Aquaculture
Publisher: John Wiley & Sons Inc
ISSN: 1753-5131
DOI / ID Number: 10.1111/raq.12522
Copyright Information:

Copyright 2020 John Wiley & Sons Australia, Ltd

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