Exercise to exhaustion leads to severe metabolic, acid-base and ionic changes in fish. It has been shown that several abiotic and biotic factors can limit burst exercise performance and the recovery process in fish. This article reviews the importance of body size, temperature, fasting/starvation and training on the ability of fish to perform and recover from exhaustive exercise. It is concluded that the constraints placed on a fish prior to and following exercise reflects the large intra-specific variability in the physiological response to exercise in fish.

Limits to Exhaustive Exercise in Fish

Observations of climate impacts on ecosystems highlight the need for an understanding of organismal thermal ranges and their implications at the ecosystem level. Where changes in aquatic animal populations have been observed, the integrative concept of oxygen- and capacitylimited thermal tolerance (OCLTT) has successfully characterised the onset of thermal limits to performance and field abundance. The OCLTT concept addresses the molecular to whole-animal mechanisms that define thermal constraints on the capacity for oxygen supply to the organism in relation to oxygen demand. The resulting ‘total excess aerobic power budget’ supports an animal’s performance (e.g. comprising motor activity, reproduction and growth) within an individual’s thermal range. The aerobic power budget is often approximated through measurements of aerobic scope for activity (i.e. the maximumdifference between resting and the highest exerciseinduced rate of oxygen consumption), whereas most animals in the field rely on lower (i.e. routine) modes of activity. At thermal limits, OCLTT also integrates protective mechanisms that extend time-limited tolerance to temperature extremes – mechanisms such as chaperones, anaerobic metabolism and antioxidative defence. Here, we briefly summarise the OCLTT concept and update it by addressing the role of routine metabolism.We highlight potential pitfalls in applying the concept and discuss the variables measured that led to the development ofOCLTT.We propose that OCLTTexplains why thermal vulnerability is highest at the whole-animal level and lowest at the molecular level. We also discuss how OCLTT captures the thermal constraints on the evolution of aquatic animal life and supports an understanding of the benefits of transitioning from water to land.

Oxygen- and capacity-limited thermal tolerance: bridging ecology and physiology

The Effects of Exercise Training on Teleost Fish, a Review of Recent Literature

Most sources of stress in aquaculture, fish salvage, stocking programs, and commercial and sport fisheries may be unavoidable. Collecting, handling, sorting, holding, and transporting are routine practices that can have significant effects on fish physiology and survival. Nevertheless, an understanding of the stressors affecting fish holding can lead to practices that reduce stress and its detrimental effects. The stress-related effects of short-term holding are influenced by water quality, confinement density, holding container design, and agonistic and predation-associated behaviors. Physiological demands (e.g., resulting from confinement-related stresses) exceeding a threshold level where the fish can no longer compensate may lead to debilitating effects. These effects can be manifested as suppressed immune systems; decreased growth, swimming performance, or reproductive capacity; even death. Furthermore, holding tolerance may depend upon the species, life stage, previous exposure to stress, and behavior of the held fish. Water quality is one of the most important contributors to fish health and stress level. Fish may be able to tolerate adverse water quality conditions; however, when combined with other stressors, fish may be quickly overcome by the resulting physiological challenges. Temperature, dissolved oxygen, ammonia, nitrite, nitrate, salinity, pH, carbon dioxide, alkalinity, and hardness are the most common water quality parameters affecting physiological stress. Secondly, high fish densities in holding containers are the most common problem throughout aquaculture facilities, live-fish transfers, and fish salvage operations. Furthermore, the holding container design may also compromise the survival and immune function by affecting water quality, density and confinement, and aggressive interactions. Lastly, fishes held for relatively short durations are also influenced by negative interactions, associated with intraspecific and interspecific competition, cannibalism, predation, and determining nascent hierarchies. These interactions can be lethal (i.e., predation) or may act as a vector for pathogens to enter (i.e., bites and wounds). Predation may be a significant source of mortality for fisheries practices that do not sort by size or species while holding. Stress associated with short-term holding of fishes can have negative effects on overall health and well-being. These four aspects are major factors contributing to the physiology, behavior, and survival of fishes held for a relatively short time period.

Stress-associated impacts of short-term holding on fishes

This perspective takes a comparative view of cardiac physiology in fish to provide insights into cardiac control mechanisms and the degree of cardiac plasticity between species Between the extremes represented by tuna and hagfish, there is a 15-fold difference in cardiac output that is largely accounted for by species differences in heart rate rather than in stroke volume The relative importance of heart rate and stroke volume is reversed in many fish in terms of explaining the up to threefold increase in cardiac output observed during swimming A conspicuous and unexplained observation is that all fish studied so far, with the exception of tuna, have heart rates lower than 120 bpm In many fish, luminal O₂, in venous blood is the sole myocardial O₂, supply, and a venous PO₂ threshold may ultimately limit cardiac performance More active fish have bigger ventricles that generally beat faster and generate higher blood pressures and flows The bigger ventricle in active fish, while improving convection to 

https://www.jstor.org/stable/info/30156237

From Hagfish to Tuna: A Perspective on Cardiac Function in Fish

Rainbow trout, Oncorhynchus mykiss, were exercise trained for 28–52 days. Trained fish were 13% larger and swam 12% faster in an aerobic swimming test. Training induced cardiac growth that was isom...

T. G. West

Papers

Effects of exercise training and coronary ablation on swimming performance, heart size, and cardiac enzymes in rainbow trout, Oncorhynchus mykiss