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Cold waters and low productivity of the reservoir create energetically special conditions for the life of aquatic organisms, which are exacerbated by the current climate change. The temperature-dependent indicators of energy metabolism (active metabolic rate) have been studied for the representatives of different ecological–iogeographic groups of amphipods: arctic (Gammaracanthus loricatus), palearctic (Gammarus zaddachi), and holarctic (G.lacustris), from the coastal lake and the littoral of the White Sea basin. Interspecific differences in the standard energy metabolism rate and its 1.5–2.0-fold increase for predating amphipods are found. [ABSTRACT FROM AUTHOR]

Abstract Advances in experimental design and equipment have simplified the collection of maximum metabolic rate (MMR) data for a more diverse array of water‐breathing animals. However, little attention has been given to the consequences of analytical choices in the estimation of MMR. Using different analytical methods can reduce the comparability of MMR estimates across species and studies and has consequences for the burgeoning number of macroecological meta‐analyses using metabolic rate data. Two key analytical choices that require standardization are the time interval, or regression window width, over which MMR is estimated, and the method used to locate that regression window within the raw oxygen depletion trace. Here, we consider the effect of both choices by estimating MMR for two shark and two salmonid species of different activity levels using multiple regression window widths and three analytical methods: rolling regression, sequential regression, and segmented regression. Shorter regression windows yielded higher metabolic rate estimates, with a risk that the shortest windows (

Advances in experimental design and equipment have simplified the collection of maximum metabolic rate (MMR) data for a more diverse array of water‐breathing animals. However, little attention has been given to the consequences of analytical choices in the estimation of MMR. Using different analytical methods can reduce the comparability of MMR estimates across species and studies and has consequences for the burgeoning number of macroecological meta‐analyses using metabolic rate data. Two key analytical choices that require standardization are the time interval, or regression window width, over which MMR is estimated, and the method used to locate that regression window within the raw oxygen depletion trace. Here, we consider the effect of both choices by estimating MMR for two shark and two salmonid species of different activity levels using multiple regression window widths and three analytical methods: rolling regression, sequential regression, and segmented regression. Shorter regression windows yielded higher metabolic rate estimates, with a risk that the shortest windows (<1‐min) reflect more system noise than MMR signal. Rolling regression was the best candidate model and produced the highest MMR estimates. Sequential regression models consistently produced lower relative estimates than rolling regression models, while the segmented regression model was unable to produce consistent MMR estimates across individuals. The time‐point of the MMR regression window along the oxygen consumption trace varied considerably across individuals but not across models. We show that choice of analytical method, in addition to more widely understood experimental choices, profoundly affect the resultant estimates of MMR. We recommend that researchers (1) employ a rolling regression model with a reliable regression window tailored to their experimental system and (2) explicitly report their analytical methods, including publishing raw data and code. [ABSTRACT FROM AUTHOR]

Coral reef ecosystems are currently under unprecedented stress due to anthropogenic induced climate change. Such stress causes coral habitats to degrade, which has been found to negatively impact the behaviour of some reef fishes. However, it is unknown whether the same chemical stresses from degraded habitats that impacts fish behaviour also impacts energy supporting swimming performance traits of fishes during the pelagic-to-reef life-history bottleneck. Here, we exposed newly settled juvenile Ambon damselfishes (Pomacentrus amboinensis) to either water that had passed over healthy or degraded coral for 24 h. Fishes were then swum at an ecologically relevant swimming speed for 200 min, and oxygen uptake rates were measured periodically. In general, fish swimming in water from degraded coral depressed oxygen uptake rates by 21%, which suggests that degraded habitats can have strong effects on fish physiology during this ecologically-critical time window. [ABSTRACT FROM AUTHOR]

Pcrit - generally defined as the PO2 below which the animal can no longer maintain a stable rate of O2 consumption (MO2), such that MO2 becomes dependent upon PO2 - provides a single number into which a vast amount of experimental effort has been invested. Here, with specific reference to water-breathers, I argue that this focus on the Pcrit is not useful for six reasons: (1) calculation of Pcrit usually involves selective data editing; (2) the value of Pcrit depends greatly on theway it is determined; (3) there is no good theoretical justification for the concept; (4) Pcrit is not the transition point from aerobic to anaerobic metabolism, and it disguises what is really going on; (5) Pcrit is not a reliable index of hypoxia tolerance; and (6) Pcrit carries minimal information content. Preferable alternatives are loss of equilibrium (LOE) tests for hypoxia tolerance, and experimental description of full MO2 versus PO2 profiles accompanied by measurements of ventilation, lactate appearance and metabolic rate by calorimetry. If the goal is to assess the ability of the animal to regulate MO2 from this profile in a mathematical fashion, promising, more informative alternatives to Pcrit are the regulation index and Michaelis-Menten or sigmoidal allosteric analyses. [ABSTRACT FROM AUTHOR]

Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance. It also suggests that, in general, the buoyancy must increase with size, and therefore, there must be ontogenetic changes within a species, with individuals getting more buoyant as they grow. Pelagic species seem to have near optimally sized fins (which minimize the cost of transport), but the majority of reef sharks could have reduced the cost of transport by increasing the size of their fins. The fact that they do not implies negative selection, probably owing to decreased manoeuvrability in confined spaces (e.g. foraging on a reef).

Metabolic rate is one of the most widely measured physiological traits in animals and may be influenced by both endogenous ( e.g. body mass) and exogenous factors ( e.g. oxygen availability and temperature). Standard metabolic rate ( SMR) and maximum metabolic rate ( MMR) are two fundamental physiological variables providing the floor and ceiling in aerobic energy metabolism. The total amount of energy available between these two variables constitutes the aerobic metabolic scope ( AMS). A laboratory exercise aimed at an undergraduate level physiology class, which details the appropriate data acquisition methods and calculations to measure oxygen consumption rates in rainbow trout Oncorhynchus mykiss, is presented here. Specifically, the teaching exercise employs intermittent flow respirometry to measure SMR and MMR, derives AMS from the measurements and demonstrates how AMS is affected by environmental oxygen. Students' results typically reveal a decline in AMS in response to environmental hypoxia. The same techniques can be applied to investigate the influence of other key factors on metabolic rate ( e.g. temperature and body mass). Discussion of the results develops students' understanding of the mechanisms underlying these fundamental physiological traits and the influence of exogenous factors. More generally, the teaching exercise outlines essential laboratory concepts in addition to metabolic rate calculations, data acquisition and unit conversions that enhance competency in quantitative analysis and reasoning. Finally, the described procedures are generally applicable to other fish species or aquatic breathers such as crustaceans ( e.g. crayfish) and provide an alternative to using higher (or more derived) animals to investigate questions related to metabolic physiology. [ABSTRACT FROM AUTHOR]

The relationship between body mass ( M) and metabolic rate was investigated through the assessment of active ( RA) and standard ( RS) metabolic rate at different life stages in zebrafish Danio rerio (5 day-old larvae, 2 month-old juveniles and 6 month-old adults). Scaling exponents and constants were assessed for standard ( RS = 0·273 M0·965 in mgO2 g−1 h−1) and active metabolic rate ( RA = 0·799 M0·926 in mgO2 g−1 h−1). These data provide the basis for further experiments regarding the effects of environmental factors on aerobic metabolism throughout the life cycle of this species. [ABSTRACT FROM AUTHOR]

Abstract: Metabolic competitive modes between digestion and locomotion are classified into three categories, termed the additive, digestion- and locomotion-priority modes. In nature, the caudal fin is frequently observed to sustain damage as a result of social rank, predation or disease. To test whether the metabolic mode changed differently for fish with different metabolic mode after caudal fin amputation as a consequence of intensified energy competition, we investigated the swimming performance of fasting and fed fish with and without the caudal fin in juveniles of three cyprinid fish species: qingbo (Spinibarbus sinensis, locomotion-priority mode), common carp (Cyprinus carpio, additive mode) and goldfish (Carassius auratus, digestion-priority mode). The critical swimming speed (Ucrit ) of fasting qingbo, common carp and goldfish decreased significantly by 49%, 32% and 35% after caudal fin amputation. The maximum tail beat amplitude (TBAmax ) (all three fishes), maximum tail beat frequency (TBFmax ) (only common carp and goldfish) and (or) active metabolic rate () (only common carp) increased significantly after caudal fin amputation. In the control fish, digestion let to a significantly lower Ucrit in goldfish but not in qingbo and common carp, and the of digesting common carp was higher than that of fasting fish, suggesting locomotion-priority, additive and digestion-priority metabolic modes in qingbo, common carp and goldfish, respectively. However, after fin amputation, digestion showed no effect on Ucrit in any of the three fishes, and only the digesting common carp showed a higher than their fasting counterparts. This result suggested that the metabolic mode of the goldfish changed from the digestion- to the locomotion-priority mode, whereas the metabolic mode of the other two fishes remained the same after fin amputation. The metabolic mode of the common carp showed no change after fin amputation likely due to the high flexibility of the cardio-respiratory capacity of this fish, as indicated by the increased . Although the metabolic mode remained the same, the feeding metabolism in the fin-amputated qingbo was down-regulated at a lower swimming speed than that of the control group due to the intensified competition between digestion and locomotion. The underlying mechanism for the metabolic mode change in the goldfish is not clear and needs further investigation. However, we speculated that in caudal-fin-intact goldfish, the decreased swimming efficiency, rather than irreducible digestive loading, caused a decreased Ucrit in digesting fish (i.e. false digestion-priority mode), and the metabolic mode should not be judged simply by the relative magnitude of the metabolic rates of fasting and digesting fish. [Copyright &y& Elsevier]

Standard metabolic rate (SMR) and active metabolic rate (AMR) are two fundamental physiological parameters providing the floor and ceiling in aerobic energy metabolism. The total amount of energy available within these two parameters confines constitutes the absolute aerobic scope (AAS). Previous studies on fish have found SMR to closely correlate with dominance and position in the social hierarchy, and to be highly repeatable over time when fish were provided an ad libitum diet. In this study we tested the temporal repeatability of individual SMR, AMR and AAS, as well as repeatability of body mass, in young brown trout (Salmo trutta L.) fed a moderately restricted diet (0.5-0.7% fish mass day-1). Metabolism was estimated from measurements of oxygen consumption rate (Mo2) and repeatability was evaluated four times across a 15-week period, Individual body mass was highly repeatable across the entire 15 week experimental period whereas residual body-mass-corrected SMR, AMA and AAS showed a gradual loss of repeatability over time. Individual residual SMR, AMA and AAS were significantly repeatable in the short term (5 weeks), gradually declined across the medium term (10 weeks) and completely disappeared in the long term (15 weeks). We suggest that this gradual decline in repeatability was due to the slightly restricted feeding regime. This is discussed in the context of phenotypic plasticity, natural selection and ecology. [ABSTRACT FROM AUTHOR]

Abstract: The culture of the mulloway (Argyrosomus japonicus), like many other Sciaenidae fishes, is rapidly growing. However there is no information on their metabolic physiology. In this study, the effects of various hypoxia levels on the swimming performance and metabolic scope of juvenile mulloway (0.34±0.01 kg, mean±SE, n =30) was investigated (water temperature=22 °C). In normoxic conditions (dissolved oxygen=6.85 mg l−1), mulloway oxygen consumption rate (M·o 2) increased exponentially with swimming speed to a maximum velocity (U crit) of 1.7±<0.1 body lengths s−1 (BL s−1) (n =6). Mulloway standard metabolic rate (SMR) was typical for non-tuna fishes (73±8 mg kg−1 h−1) and they had a moderate scope for aerobic metabolism (5 times the SMR). Mulloway minimum gross cost of transport (GCOTmin, 0.14±0.01 mg kg−1 m−1) and optimum swimming velocity (U opt, 1.3±0.2 BL s−1) were comparable to many other body and caudal fin swimming fish species. Energy expenditure was minimum when swimming between 0.3 and 0.5 BL s−1. The critical dissolved oxygen level was 1.80 mg l−1 for mulloway swimming at 0.9 BL s−1. This reveals that mulloway are well adapted to hypoxia, which is probably adaptive from their natural early life history within estuaries. In all levels of hypoxia (75% saturation=5.23, 50%=3.64, and 25%=1 .86 mg l−1), M·o 2 increased linearly with swimming speed and active metabolic rate (AMR) was reduced (218±17, 202±14 and 175±10 mg kg−1 h−1 for 75%, 50% and 25% saturation respectively). However, U crit was only reduced at 50% and 25% saturation (1.4±<0.1 and 1.4±<0.1 BL s−1 respectively). This demonstrates that although the metabolic capacity of mulloway is reduced in mild hypoxia (75% saturation) they are able to compensate to maintain swimming performance. GCOTmin (0.09±0.01 mg kg−1 m−1) and U opt (0.8±0.1 BL s−1) were significantly reduced at 25% dissolved oxygen saturation. As mulloway metabolic scope was significantly reduced at all hypoxia levels, it suggests that even mild hypoxia may reduce growth productivity. [Copyright &y& Elsevier]

Abstract: The Barents Sea capelin, a schooling species, undertakes extensive migrations against the predominating current north of Norway to its spawning grounds along the Norwegian and Russian coasts. Low swimming costs (i.e. high efficiency) at cruising speeds would be advantageous for capelin, enabling allocation of more energy to reproduction. A high oxygen uptake capacity may however also be beneficial, considering the difficulty of strenuous swimming against the predominant current, and to avoid predators. To investigate the swimming energetics of the Barents Sea capelin, the relationship between rate of oxygen uptake, MO2 (mg O2 kg−1 h−1), and swimming speed was investigated at 5 °C. A power and an exponential function described the correlation between MO2 and swimming speed almost equally well as determined by the correlation coefficient. The power function described the relationship as MO2 =101.624+43.5U 2.042, where U was the swimming speed in body lengths per second (bl s−1) and 101.6 an estimate of the standard metabolic rate (SMR, mg O2 kg−1 h−1). The exponential function gave MO2 =85.747e0.591U with U being the swimming speed (bl s−1) and 85.7 an estimate of the SMR (mg O2 kg−1 h−1). The active metabolic rate (AMR, mg O2 kg−1 h−1), the oxygen uptake measured at the critical swimming speed (U crit), was 532 mg O2 kg−1 h−1, hence resulting in a scope for activity (SFA) of 5.2 or 6.2, depending on the model for SMR estimation. The capelin was able to sustain U crit of 3 bl s−1, or ∼51 cm s−1. The relationship between cost of transport (COT) and swimming speed was characteristically U-shaped, with minimum cost of transport (COTmin) between 218 and 225 mg O2 kg−1 km-1, at an optimal swimming speed (U opt) within the range of 1.5 to 1.7 bl s−1. The swimming energetics of capelin was related to its migratory behaviour and the results compared to other pelagic species. Finally, the limitations involved with working with a schooling species were discussed, in addition to how choice of model for description of costs associated with swimming generally may influence parameter estimation. [Copyright &y& Elsevier]

Hypoxia and petrogenic hydrocarbon contamination are two anthropogenic stressors that coexist in coastal environments. Although studies have estimated the impact of each stressor separately, few investigations have assessed the effects of these stressors in interaction. We therefore investigated the impact of these combined stressors on sea bass, (Dicentrarchus labrax) physiology. After experimental contamination with physically dispersed oil, fish were exposed to hypoxia or normoxia, and active/standard metabolic rates (AMR and SMR, respectively), and metabolic scope (MS) were estimated. At the protocol's end, the uptake of polycyclic aromatic hydrocarbons (PAHs) was estimated by evaluating relative concentrations of bile metabolites. In terms of bile metabolites, our results validated the uptake of PAHs by contaminated fish in our experimental settings, and further suggest that the hypoxic period after contamination does not reduce or increase compound metabolization processes. Our data showed significant effects of hypoxia on all metabolic rates: a significant drastic AMR reduction and significant SMR diminution led to decreased MS. We also found that oil contamination significantly impacted AMR and MS, but not SMR. These results suggested that when evaluated separately, hypoxia or oil affect the metabolic rate of sea bass. On the other hand, when evaluated in combination, no cumulative effects were observed, since fish exposed to both stressors did not show a stronger impact on metabolism than fish exposed to hypoxia alone. This suggests that oil impacts fish metabolism when fish occupy normoxic waters, and that oil does not magnify hypoxia-induced effects on fish metabolism. • This study investigates the effects of oil and hypoxia on fish metabolism. • Variables measured were active, standard metabolic rates as well as metabolic scope. • Results revealed an effect of hypoxia on all metabolic variables. • Dispersed oil affected active metabolic rate and metabolic scope. • Combination of both stressors did not induce synergistic nor additive effects [ABSTRACT FROM AUTHOR]