Chabot 2016 J Fish Biol.pdf (original) (raw)

EDITORIAL Metabolic rate in fishes: definitions, methods and significance for conservation physiology There is a growing interest in the potential for physiological tools and know-how to be applied in conservation research, the emerging field of conservation physiology. For fishes, there is a long-standing hypothesis whereby their bioenergetics and respiratory physiology should be of particular significance for their ecological performance (Fry, 1971). Water can be challenging as a respiratory medium, because it only contains a few milligrams of oxygen per litre (Schmidt-Nielsen, 1990). The physiology and oxygen demands of ectothermic fishes can be profoundly affected by environmental temperature. Oxygen can also easily become depleted in aquatic habitats, and such episodes of hypoxia are becoming more prevalent because of human effects (Diaz & Rosenberg, 1995; Breitburg et al., 2009). It has been argued, therefore, that the capacity of fishes to provide oxygen for vital processes and important activities, such as swimming or digesting and assimilating food, may define the habitats they can colonize successfully (Fry, 1971). As such, there is interest in how traits of metabolism and energetics may be applied in conservation physiology. Such applications can be direct, in experimental contexts, and also indirect, to parameterize models to project the potential effects of environmental changes, such as eutrophication, contamination and ongoing climate change. A core element of energetics is, of course, the metabolic rate that, in fishes, is typically measured as rate of oxygen uptake. There has been a surge in interest for measuring oxygen uptake in fishes but newcomers to the field may well find the terminology and definitions for major metabolic traits confusing. Further, methods and protocols are dispersed throughout the literature, without much integration and comparison. This special issue (SI) arose to respond to these issues, following conversations among fish ecophysiologists at conferences organized within the context of the European Cooperation in Science and Technology (COST) Action Conservation Physiology of Marine Fishes (COST FA1004). The first objective of this SI was to provide literature reviews for the major metabolic traits and recommend appropriate techniques to measure and calculate different metabolic rates. This includes instructions to construct appropriate experimental setups and software to analyse the data. That is, the aim was to make this SI the essential guide that ecophysiologists can consult before planning experiments to measure the metabolic rate of fishes. To this effect, the SI provides 13 papers that explain why the metabolic rate of fishes can be estimated by measuring oxygen uptake, and discuss the different levels of metabolic rate that are of interest, and terminology to deal with metabolic capacity and shortages of dissolved oxygen (hypoxia). These papers provide detailed instructions for proper design of equipment and protocols to measure these metabolic traits accurately and reliably in fishes in the laboratory, 1