Critical Swimming Speed Research Articles

Assessment of behavioural and physiological traits as indicators of suitability for European perch aquaculture

Domestication and selective breeding can mitigate current bottlenecks in European perch aquaculture. Monitoring the condition and stress tolerance of European perch stocks from different recirculating aquaculture systems is of general interest to set the baseline values of promising candidates for further breeding processes. We recorded morphometric, behavioural (critical swimming speed, activity, aggressiveness, propensity to approach a novel object), and physiological parameters (plasma cortisol, glucose, ion concentrations, enzyme activity levels) after stress induction across four European perch stocks obtained from different aquaculture facilities in France (I and II), Denmark, and Hungary. The European perch stock from Denmark revealed the population with the most pronounced activity pattern. This was reflected by the highest relative swimming speed and a high percentage of bold-exploratory behaviour, which coincides with increased aggressive interactions within this stock. Additionally, we detected a higher tolerance to adverse environmental challenges in the perch stock from Denmark compared with the stocks from France and Hungary. The observed characteristics suggest that the stock from Denmark has a higher potential in the future framework of selective-breeding assessment. Further in-depth research is required to elucidate which traits and genetic as well as epigenetic components accelerate the domestication processes of European perch aquaculture and promote selective breeding processes.

Exercise, programmed cell death and exhaustion of cardiomyocyte proliferation in aging zebrafish.

ABSTRACTExercise may ameliorate the eventual heart failure inherent in human aging. In this study, we use zebrafish to understand how aging and exercise affect cardiomyocyte turnover and myocardial remodelling. We show that cardiomyocyte proliferation remains constant throughout life but that onset of fibrosis is associated with a late increase in apoptosis. These findings correlate with decreases in voluntary swimming activity, critical swimming speed (Ucrit), and increases in biomarkers of cardiac insufficiency. The ability to respond to severe physiological stress is also impaired with age. Although young adult fish respond with robust cardiomyocyte proliferation in response to enforced swimming, this is dramatically impaired in older fish and served by a smaller proliferation-competent cardiomyocyte population. Finally, we show that these aging responses can be improved through increased activity throughout adulthood. However, despite improvement in Ucrit and the proliferative response to stress, the size of the proliferating cardiomyocyte population remained unchanged. The zebrafish heart models human aging and reveals the important trade-off between preserving cardiovascular fitness through exercise at the expense of accelerated fibrotic change.

Swimming capability of target fish from eight hydropower stations in China relative to fishway design

The four major Chinese carp (MC), Schizothorax fish species (SF), and Cobitidae fish species (CF) are the most important target fish species in China. The swimming behaviour study of three target fish groups is the key to Chinese fishway designs. The 20 min critical swimming speed (Ucrit-20 min) and endurance of the target fish species in relation to body length, swimming speed, and water temperature were estimated using multiple linear regression. The results indicated that both fish body length and water temperature had a significant effect on swimming capability. Performance comparisons indicated that SF were remarkably strong swimmer. CF possess slightly greater swimming capability than MC. The entrance velocity of the upstream fishway should be greater than Ucrit-20 min, but less than maximum swimming speed to make the flow out of the fishway noticeable. The maximum swimming distance could be estimated using endurance model at flow velocity of 1.2 m·s–1. For the downstream-migrating juvenile fish, it was suggested that the flow velocity of turbine intake should be less than maximum sustained speed avoiding entering turbine.

Heritable variation in swimming performance in Nile tilapia (Oreochromis niloticus) and negative genetic correlations with growth and harvest weight

Nile tilapia is predominantly produced in smallholder ponds without aeration. We hypothesize that Nile tilapia with high oxygen uptake efficiency (O2UE) may perform better under these conditions than Nile tilapia with low O2UE. Critical swimming speed (Ucrit, in cm s−1) is a potential indicator for O2UE. Our objectives were to estimate variance components for Ucrit and fish size at swim testing early in life, and genetic correlations (rg) between Ucrit with harvest weight (HW) and daily growth coefficient (DGC) later after grow-out in a non-aerated pond. Substantial heritability was found for absolute Ucrit (0.48). The estimated rg between absolute Ucrit and fish size at testing were all strong and positive (range 0.72–0.83). The estimated rg between absolute Ucrit and HW, and absolute Ucrit and DGC were − 0.21 and − 0.63 respectively, indicating that fish with higher absolute Ucrit had lower growth in the non-aerated pond as compared to fish with lower absolute Ucrit. These results suggest a juvenile trade-off between swimming and growth performance where fish with high Ucrit early in life show slower growth later under conditions of limited oxygen availability. We conclude that Ucrit in Nile tilapia is heritable and can be used to predict growth performance.

A Method for Estimating the Velocity at Which Anaerobic Metabolism Begins in Swimming Fish

Anaerobic metabolism begins before fish reach their critical swimming speed. Anaerobic metabolism affects the swimming ability of fish, which is not conducive to their upward tracking. The initiation of anaerobic metabolism therefore provides a better predictor of flow barriers than critical swimming speed. To estimate the anaerobic element of metabolism for swimming fish, the respiratory metabolism and swimming performance of adult crucian carp (Carassius auratus, mass = 260.10 ± 7.93, body length = 19.32 ± 0.24) were tested in a closed tank at 20 ± 1 °C. The swimming behavior and rate of oxygen consumption of these carp were recorded at various swimming speeds. Results indicate (1) The critical swimming speed of the crucian carp was 0.85 ± 0.032 m/s (4.40 ± 0.16 BL/s). (2) When a power function was fitted to the data, oxygen consumption, as a function of swimming speed, was determined to be AMR = 131.24 + 461.26Us1.27 (R2 = 0.948, p < 0.001) and the power value (1.27) of Us indicated high swimming efficiency. (3) Increased swimming speed led to increases in the tail beat frequency. (4) Swimming costs were calculated via rate of oxygen consumption and hydrodynamic modeling. Then, the drag coefficient of the crucian carp during swimming was calibrated (0.126–0.140), and the velocity at which anaerobic metabolism was initiated was estimated (0.52 m/s), via the new method described herein. This study adds to our understanding of the metabolic patterns of fish at different swimming speeds.

Long lasting effects of early temperature exposure on the swimming performance and skeleton development of metamorphosing Gilthead seabream (Sparus aurata L.) larvae

Temperatures experienced during early ontogeny significantly influence fish phenotypes, with clear consequences for the wild and reared stocks. We examined the effect of temperature (17, 20, or 23 °C) during the short embryonic and yolk-sac larval period, on the swimming performance and skeleton of metamorphosing Gilthead seabream larvae. In the following ontogenetic period, all fish were subjected to common temperature (20 °C). The critical swimming speed of metamorphosing larvae was significantly decreased from 9.7 ± 0.6 TL/s (total length per second) at 17 °C developmental temperature (DT) to 8.7 ± 0.6 and 8.8 ± 0.7 TL/s at 20 and 23 °C DT respectively (p < 0.05). Swimming performance was significantly correlated with fish body shape (p < 0.05). Compared with the rest groups, fish of 17 °C DT presented a slender body shape, longer caudal peduncle, terminal mouth and ventrally transposed pectoral fins. Moreover, DT significantly affected the relative depth of heart ventricle (VD/TL,p < 0.05), which was comparatively increased at 17 °C DT. Finally, the incidence of caudal-fin abnormalities significantly decreased (p < 0.05) with the increase of DT. To our knowledge, this is the first evidence for the significant effect of DT during the short embryonic and yolk-sac larval period on the swimming performance of the later stages.

What is the limit of sustained swimming in Atlantic salmon post smolts?

A trend in Atlantic salmon aquaculture is to establish new production sites that are susceptible to extreme weather conditions; however, strong and persistent water currents may compromise fish welfare. Defining acceptable current conditions necessitates an assessment of sustained swimming abilities that are fuelled solely by aerobic metabolism and do not result in fatigue. In this study, the limit of sustained swimming was quantified with regards to both speed and time in Atlantic salmon of ~700 g and ~39 cm at 12°C by testing fish in groups of 10 in a large swim tunnel respirometer. First, critical swimming speed (Ucrit) (107 cm s-1) and minimum cost of transport (66 cm s-1) were measured. Sustained swimming trials at constant speeds were then performed based on a percentage of the group mean Ucrit (80, 85, 90, 95, 100 or 105%). Fish were forced to swim until they fatigued or until 72 h had passed. Surprisingly, most fish were able to sustain 80 and 85% Ucrit for 72 consecutive hours. However, at the highest speeds, fatigue was reached within the first 2 h. By categorizing fatigue times of individual fish into &lt;2, 2-72 or &gt;72 h, significant differences in relative swimming speeds were found that corresponded to 2.7, 2.5 and 2.2 body lengths s-1, respectively. These results document impressive sustained swimming capacities in farmed Atlantic salmon and add important temporal insights about ambient current limits with regards to fish welfare at exposed aquaculture sites.

Does dietary Tenebrio molitor affect swimming capacity, energy use, and physiological responses of European perch Perca fluviatilis?

We assessed swimming capacity, energy expenditure, and physiological responses of European perch (Perca fluviatilis) fed four isonitrogenous and isoenergetic diets containing yellow mealworm (Tenebrio molitor) larvae meal at 0, 25, 50, and 75% substitution for fishmeal (abbreviated diets, TM0, TM25, TM50, and TM75). Each diet was fed to quadruplicate group of perch (initial biometrics, body weight 20.81 ± 3.36 g, total length 11.77 ± 0.72 cm) for 119 days. At the terminal of feeding trial following 24 h starvation, eighty fish (20 fish/diet group) were individually selected for swimming performance tests, which were conducted in a 10 L enclosed swimming tunnel with velocity increased from 5 cm/s in 2 cm/s increments every 60 s. Exercised fish, fish experienced swimming tests, and non-exercised fish, fish not involved in swimming tests were, at the same time, sampled for serum biochemistry, muscle traits. Whole-body of non-exercised fish were also analyzed for proximate composition and fatty acid profile.Critical swimming speed (Ucrit, cm/s and body length/s), oxygen consumption (MO2, mg/kg/h), and energy cost of transport (COT, J/kg/m) of perch did not differ among diet treatments. Exercised perch significantly increased serum glucose and cortisol compared to non-exercised fish. Substitution of fishmeal by T. molitor larvae meal induced significant changes in aspartate aminotransferase across treatment groups, lactate dehydrogenase in TM0 and TM75, K+ concentration in fish fed TM75, and muscle water content in TM50 of exercised compared to non-exercised perch. Oleic acid of whole-body fish had a significant linear correlation with the critical swimming speed of European perch. Since fish swimming behavior is an indicator of animal welfare, our findings suggest that dietary insect meals could ensure the welfare of farmed fish.

From 95 to 59 millimetres: a new active acoustic tag size guideline for salmon

Two laboratory studies evaluated small Chinook salmon (Oncorhynchus tshawytscha) (36–99 mm fork length (FL), 0.7%–26.7% tag burden) survival, tag retention, and growth (n = 539) and critical swimming speed (Ucrit; n = 241). Fish were implanted with a new active acoustic tag and compared with untagged controls at 12 and 17 °C. Across studies, no temperature differences were detected. All control fish survived. All tagged fish ≥58 mm FL survived and retained their tags. Regression models predicted ≥98.6% survival and retention for tagged fish ≥58.6 mm FL or ≥1.9 g (4.2% tag burden). No growth differences among treatments were identified. Spline regression analysis indicated Ucrit was similar for control and tagged fish that measured ≥57.3 mm FL. We recommend tagging salmon ≥59 mm FL or ≥1.9 g (≤4.2% tag burden), although the guideline should be confirmed in a field setting. Study results represent an important step towards using the new active tag in acoustic telemetry field studies that estimate short-term (30-day) survival of small salmonids.

Oxygen stress and reproduction do not impede aerobic performance in adult eastern mosquitofish (Gambusia holbrooki)

Physiological traits are key determinants of species success in any given environment. Competing metabolic demands can influence success by limiting the available scope for aerobically-demanding activities, including reproduction and dispersal. The present study investigated whether the aerobic performance of Gambusia holbrooki, one of the most invasive species in the world, was affected by the embryonic demands of pregnancy and whether these demands were compounded in a hypoxic environment. To quantify these effects, we measured the resting metabolic rate (RMR) and critical swimming speed (Ucrit) of wild-caught adult mosquitofish in saturated oxygen conditions, and following chronic exposure to hypoxic or hyperoxic water. Contrary to expectations, the RMR and Ucrit of gravid females was equal to that of non-gravid females and males, once the significant effects of body mass on these traits was accounted for. Whilst the exposure studies demonstrated that RMR changes subject to oxygen availability, overall aerobic performance does not. These findings suggest that mosquitofish metabolism is adapted for continued reproductive function and dispersal in low oxygen environments, which are essential for establishing and replenishment of populations. The ability of this species to tolerate hypoxia may confer a competitive advantage relative to native species, especially in disturbed lentic environments where prolonged periods of hypoxia are more common. Given their live-bearing mode of reproduction and resilience to the metabolic demands of reproduction, even in low oxygen conditions, we suggest that the physiology of female mosquitofish is a significant contributor to the invasion success and persistence of the species.

The effect of fasting period on swimming performance, blood parameters and stress recovery in Atlantic salmon post smolts

In this study, Atlantic salmon post smolts (~250 g, ~29 cm) were fasted for four weeks at 12 °C in full strength seawater. During this period, the critical swimming speed (Ucrit) was measured after 1, 2 and 4 weeks of fasting, as well as in a fed control group. Furthermore, blood samples were taken in each treatment group prior to the swim test, at fatigue, and following 3 h and 24 h of subsequent recovery. Four weeks of fasting gradually reduced the condition factor from 1.03 to 0.89. However, the Ucrit remained statistically unaffected at 3.5 body lengths s−1. Exhaustive exercise stress caused large increases in plasma osmolality, [Cl−], [Na+], [Ca2+], [lactate] and [cortisol], while haematocrit and [haemoglobin] also increased. Plasma ions and lactate had increased further after 3 h recovery, and osmolality, [Cl−] and [Na+] were still elevated above control levels after 24 h while other blood parameters were fully recovered. Osmotic disturbances may therefore be considered the most challenging stressor during strenuous exercise in seawater. Only minor effects of fasting period on blood parameters in response to exhaustive exercise were detected, which included slightly higher osmotic disturbances and a repressed response in red blood cell recruitment at fatigue in fasted fish. Furthermore, the 4-week fasting group had a reduced cortisol response following fatigue compared to the other treatment groups. In conclusion, these results show that Atlantic salmon maintain their full swimming capacity as well as their ability to respond and recover from acute stress during an extended period of food deprivation.

Climate change and anadromous fish: How does thermal acclimation affect the mechanics of themyotomal muscle of theAtlantic salmon, Salmo salar?

In response to accelerated temperature shifts due to climate change, the survival of many species will require forms of thermal acclimation to their changing environment. We were interested in how climate change will impact a commercially and recreationally important species of fish, Atlantic salmon (Salmo salar). As climate change alters the thermal environment of their natal streams, we asked how their muscle function will be altered by extended exposure to both warm and cold temperatures. We performed a thermal acclimation study of S. salar muscle mechanics of both fast-twitch, or white, and slow-twitch, or red, myotomal muscle bundles to investigate how temperature acclimated Atlantic salmon would respond across a range of different temperatures. Isometric contraction properties, maximum shortening velocity, and oscillatory power output were measured and compared amongst three groups of salmon-warm acclimated (20°C), cold-acclimated (2°C), and those at their rearing temperature (12°C). The Atlantic salmon showed limited thermal acclimation in their contraction kinetics, and some of the shifts in contractile properties that were observed would not be predicted to mitigate the impact of a warming environment. For instance, the maximum shortening velocity at a common test temperature was higher in the warm acclimated group and lower in the cold-acclimated group. In addition, critical swimming speed did not vary with temperature of acclimation when tested at a common temperature (12°C). Our results suggest that Atlantic salmon populations will continue to struggle in response to a warming environment.

温度对中华倒刺鲃不同生理生态性能的影响:驯化有益假说的验证

驯化有益假说（Beneficial acclimation hypothesis）认为生物表型的适应性变化会增强其在诱导这些变化产生的环境中的生理机能或适合度。然而，由于动物不同生理生态性能对环境驯化的响应可能不一致，那么，测试表型性状的选择对驯化有益假说的验证就尤为关键。为此，整合表征动物生存适合度的不同生理生态性能并探究其对环境驯化的响应模式就十分必要。以我国长江中上游广泛分布的中华倒刺鲃（Spinibarbus sinensis）为对象，考察了驯化温度（18℃、28℃）和测试温度（18℃、28℃）及其交互作用对该物种有氧运动能力和无氧运动能力的影响，为驯化有益假说等相关假说的验证提供参考。研究发现，中华倒刺鲃不同生理生态性能对温度驯化的响应存在差异：（1）驯化温度对表征中华倒刺鲃无氧运动能力的快速启动游泳无显著影响（除最大加速度外）（P>0.05），研究数据倾向于支持无益假说（No-advantage hypothesis）；（2）驯化温度对表征中华倒刺鲃有氧运动能力的临界游泳速度（Critical swimming speed，U_crit）和最大代谢率（Maximum metabolic rate，MMR）影响显著（P<0.05），18℃驯化-18℃测试下的U_crit和MMR均优于28℃驯化-18℃测试下的U_crit和MMR，结果部分支持驯化有益假说和冷有益假说（Cooler is better hypothesis）；（3）驯化温度、测试温度、游泳速度对中华倒刺鲃的运动代谢率（Active metabolic rate，MO₂）和单位距离能量消耗（The energetic cost of transport，COT）影响显著（P<0.05）。值得关注的是，当游泳速度小于30 cm/s时，驯化温度对MO₂和COT无影响，结果支持无益假说；而当游泳速度大于30 cm/s时，在特定的流速下经过28℃驯化的中华倒刺鲃无论在28℃还是18℃的测试环境下MO₂和COT均较低，结果倾向于支持热有益假说（Warmer is better hypothesis）。研究结果提示：驯化有益假说并不具有普遍性，热驯化相关假说的验证不仅受表型性状选择的影响，而且还与测试的环境选择压力有关。;Traditionally, it has been assumed that all acclimation changes to the phenotype enhanced the performance of an individual organism in the environment in which those changes were induced (beneficial acclimation hypothesis, BAH). However, since the responses of different eco-physiological properties of animals to acclimation may be inconsistent, the phenotypes selected for testing are particularly critical for the verification of BAH. Thus, it is necessary to integrate different eco-physiological properties that characterize the fitness of the organism and to explore their response mode to acclimation. To verify the hypotheses (e.g. BAH) related to thermal acclimation, Spinibarbus sinensis, which is widely distributed in the middle and upper reaches of the Yangtze river in China, was taken as the object to investigate the effects of acclimation temperature (18℃ and 28℃) and test temperature (18℃ and 28℃), as well as their interactions on the aerobic and anaerobic swimming performance of this species. We confirmed that the responses of different eco-physiological properties in S. sinensis to temperature acclimation were not consistent. (1) In addition to maximum linear acceleration (A_max), acclimation temperature had no significant influence on maximum linear velocity (V_max), latency time (T_Latency) and escape distance during the first 120 ms after the stimulus (S_{120 ms}) that characterize fast-start performance of S. sinensis (P>0.05). The data tend to support no-advantage hypothesis. (2) Acclimation temperature had a significant effect on critical swimming speed (U_crit) and maximum metabolic rate (MMR) that characterize aerobic swimming performance of S. sinensis (P<0.05). The U_crit and MMR of the individuals acclimated to 18℃ and tested at 18℃ outperformed than those acclimated to 28℃ and tested at 18℃. The data tend to support the BAH as well as cooler is better hypothesis at least in part. (3) Both acclimation temperature, test temperature and water velocity had significant effects on active metabolic rate (MO₂) and the energetic cost of transport (COT) in S. sinensis (P<0.05). Interestingly, acclimation temperature had no effect on MO₂ and COT when the swimming speed was less than 30 cm/s, and in that case no-advantage hypothesis was supported. Whereas the MO₂ and COT of the individuals acclimated to 28℃ were lower than those acclimated to 18℃ no matter the test temperature was 28℃ or 18℃ at a specific flow rate (greater than 30 cm/s), and in that case warmer is better hypothesis was supported. Overall, the data from our studies rejected the generality of the BAH. The results indicated that the verification of the BAH was not only influenced by the choice of phenotypic traits, but also strongly affected by the selection pressure of the test environment.

Automated flow control of a multi-lane swimming chamber for small fishes indicates species-specific sensitivity to experimental protocols.

In fishes, swimming performance is considered an important metric to measure fitness, dispersal and migratory abilities. The swimming performance of individual larval fishes is often integrated into models to make inferences on how environmental parameters affect population-level dynamics (e.g. connectivity). However, little information exists regarding how experimental protocols affect the swimming performance of marine fish larvae. In addition, the technical setups used to measure larval fish swimming performance often lack automation and accurate control of water quality parameters and flow velocity. In this study, we automated the control of multi-lane swimming chambers for small fishes by developing an open-source algorithm. This automation allowed us to execute repeatable flow scenarios and reduce operator interference and inaccuracies in flow velocity typically associated with manual control. Furthermore, we made structural modifications to a prior design to reduce the areas of lower flow velocity. We then validated the flow dynamics of the new chambers using computational fluid dynamics and particle-tracking software. The algorithm provided an accurate alignment between the set and measured flow velocities and we used it to test whether faster critical swimming speed (U crit) protocols (i.e. shorter time intervals and higher velocity increments) would increase U crit of early life stages of two tropical fish species [4-10-mm standard length (SL)]. The U crit of barramundi (Lates calcarifer) and cinnamon anemonefish (Amphiprion melanopus) increased linearly with fish length, but in cinnamon anemonefish, U crit started to decrease upon metamorphosis. Swimming protocols using longer time intervals (more than 2.5 times increase) negatively affected U crit in cinnamon anemonefish but not in barramundi. These species-specific differences in swimming performance highlight the importance of testing suitable U crit protocols prior to experimentation. The automated control of flow velocity will create more accurate and repeatable data on swimming performance of larval fishes. Integrating refined measurements into individual-based models will support future research on the effects of environmental change.

Oxygen uptake, heart rate and activities of locomotor muscles during a critical swimming speed protocol in the gilthead sea bream Sparus aurata.

Oxygen uptake, heart rate and contraction frequencies of slow oxidative (SO) and fast glycolytic (FG) muscle were measured simultaneously in gilthead seabream Sparus aurata submitted to stepwise increases in current speed in a swimming respirometer. Variation in oxygen uptake was closely related to variation in heart rate, over initial steps these rose in concert with an increase in contraction frequency of SO muscle. There was an asymptote in oxygen uptake and heart rate at high speeds that reflected a transition from exclusive use of aerobic SO muscle to a combination of SO and anaerobic FG muscle, and which preceded fatigue.

The pharmaceutical prednisone affects sheepshead minnow (Cyprinodon variegatus) metabolism and swimming performance

High usage of the synthetic glucocorticoids (GCs) has led to significant presence of this pharmaceutical group in surface waters where it can affect non-target organisms such as fish. Assessment of a fish's metabolism and swimming performance provide reliable sub-lethal measures of effects of GCs on oxygen-requiring processes and ability to swim. In this study, we determined time-dependent (7, 14 and 21 days) effects of the synthetic GC prednisone (1 μg L−1) on sheepshead minnow (SHM) (Cyprinodon variegatus). Standard (SMR), routine (RMR) and maximum (MMR) metabolic rate, metabolic scope (MS), excess post-exercise oxygen consumption (EPOC), cost of transport (COT) and critical swimming speed (Ucrit) were determined. Twenty-one days exposure to prednisone resulted in significantly higher SMR, RMR, MMR, MS, EPOC and COT compared with 7d and 14d prednisone fish. However, Ucrit was not significantly different between prednisone and solvent control exposed fish (within 7d, 14d, 21d groups). SMR, RMR and MMR were lower in the 7d and 14d prednisone exposed fish compared with their solvent control groups. In contrast, SMR, RMR and MMR were all significantly higher in the 21d prednisone exposed fish compared with solvent control. EPOC was significantly higher in 14d prednisone exposed fish and trending higher in 21d and 7d prednisone exposed fish compared with their solvent controls. EPOC was significantly higher in 21d compared with 7d prednisone exposed fish. A significantly higher COT was seen in the 21d compared with 7d and 14d prednisone fish. Collectively, this study showed time-dependent effects of prednisone on SHM metabolism and swimming performance.

An acute increase in water temperature can decrease the swimming performance and energy utilization efficiency in rainbow trout (Oncorhynchus mykiss).

In order to evaluate the effects of acute temperature exposure on the swimming performance of rainbow trout (Oncorhynchus mykiss), the critical swimming speed (Ucrit) and oxygen consumption rates (MO2) were determined at different temperatures (13.2, 18.4, and 22.5°C). The Ucrit and MO2 of different body mass (109.44, 175.74, and 249.42g) fish were also obtained at 13.4°C. The Ucrit first increased as the temperature increased from 13.2 to 15.2°C, which was calculated to be the optimal temperature for the Ucrit, and then decreased with increasing temperature. The optimal swimming speed (Uopt) showed a similar trend to the Ucrit. At a given swimming speed, the MO2 and cost of transport (COT) were significantly higher at 22.5 than at 13.2°C, suggesting the energy utilization efficiency decreased with increasing temperature. The absolute values of Ucrit and Uopt increased as the body mass increased from 109.44 to 249.42g, whereas the relative values decreased. Although not statistically significant, the maximum metabolic rate (MMR) tended to increase with temperature but decrease with body mass. Results can be of value in understanding the behavioral and physiological response of rainbow trout to acute temperature change.

Key factors explaining critical swimming speed in freshwater fish: a review and statistical analysis for Iberian species

Swimming performance is a key feature that mediates fitness and survival in aquatic animals. Dispersal, habitat selection, predator–prey interactions and reproduction are processes that depend on swimming capabilities. Testing the critical swimming speed (Ucrit) of fish is the most straightforward method to assess their prolonged swimming performance. We analysed the contribution of several predictor variables (total body length, experimental water temperature, time step interval between velocity increments, species identity, taxonomic affiliation, native status, body shape and form factor) in explaining the variation of Ucrit, using linear models and random forests. We compiled in total 204 studies testing Ucrit of 35 inland fishes of the Iberian Peninsula, including 17 alien species that are non-native to that region. We found that body length is largely the most important predictor of Ucrit out of the eight tested variables, followed by family, time step interval and species identity. By contrast, form factor, temperature, body shape and native status were less important. Results showed a generally positive relationship between Ucrit and total body length, but regression slopes varied markedly among families and species. By contrast, linear models did not show significant differences between native and alien species. In conclusion, the present study provides a first comprehensive database of Ucrit in Iberian freshwater fish, which can be thus of considerable interest for habitat management and restoration plans. The resulting data represents a sound foundation to assess fish responses to hydrological alteration (e.g. water flow tolerance and dispersal capacities), or to categorize their habitat preferences.

The impact of training according critical swimming speed that uses tempo trainer pro in level of aerobic abilities in 400 meters freestyle swimming of advanced ones

The paper aims at: - Finding out the indication of differences of aerobic abilities between pre and post-tests of both experimental and control groups. - Finding out the indication of differences of aerobic abilities of post-tests of both experimental and control groups. The researchers uses the experimental method since it suits the paper concept. The experiment was applied on a target of the Iraqi National Team advanced swimmers of 400 m freestyle swimming, (12) ones, so that the target is a collective one. Those 12 were classified into two groups of( 6) members each: experimental and control groups. The similarity of (height, weight, training and time ages) variables was done, in addition to the equivalence of (performance modeling, both Anaerobic and aerobic abilities and achievement) variables between both groups. Then, the experimental design was used by the researcher, which is entitled the equivalent groups of both pre and post-tests design, a matter that made the experimental group apply the experimental method of an independent variable (training strategy by performance modeling of critical swimming speed that uses tempo trainer pro) which is a training strategy the researcher put to achieve a good( 400) m freestyle swimming, getting the way of dividing the regular distance, grouping the level of training capacity to get the best performance of the critical swimming speed to go with Anaerobic threshold speed of each swimmer, decreasing the lost time during that competition, and other training and strategic goals. After that, the researcher interrelated with the Iraqi National Team method of( 400) m freestyle swimming during competition periods so as the experimental group could be applicable for him on his paper achieving days: four days a week and it lasted for six weeks. During that period, the experimental group had done( 24 ) training units that applied the independent variable. A number of scouting experiments were done before the application of the method on the paper target by the support of the assistant team, followed by a number of specialized tests on swimming from various and modern resources which had never been used and applied in our local and regional reality. Therefore, they had been grouped into our local reality through the achieving of the scientific factors. Furthermore, new statistical equations were used to achieve the tests: modeling and critical swimming speed ones. Also, relevant and independent T tests were used to get the experimental outcomes. imported system (Tempo trainer pro) was also used to help achieving the paper aims together with pulse measuring watch (polar type). The outcomes were fatherly discussed to help the researchers get the following concluding points: There is a significant impact of adopting the critical swimming speed (CSS) as a criterion for codifying the training load in the curriculum prepared for the experimental group, which in turn contributed to the development of the level of work of energy production systems and the improvement of functional adaptations of the members of the experimental group and thus its superiority over its control counterpart in the anaerobic and air capacity variables.

The impact of training strategy by performance that uses tempo trainer pro in achievement to 400 meters freestyle swimming for Iraqi national tame advanced ones

- Finding out the indication of differences of achievement between pre and post-tests of both experimental and control groups. - Finding out the indication of differences of achievement of post-tests of both experimental and control groups. - Finding out the indication of differences of the impact of training strategy by performance modeling that uses tempo trainer pro between both experimental and control groups in the post-tests. The researchers uses the experimental method since it suits the paper concept. The experiment was applied on a target of the Iraqi National Team advanced swimmers of 400 m freestyle swimming, (12) ones, so that the target is a collective one. Those 12 were classified into two groups of( 6) members each: experimental and control groups. The similarity of (height, weight, training and time ages) variables was done, in addition to the equivalence of (performance modeling, both Anaerobic and aerobic abilities and achievement) variables between both groups. Then, the experimental design was used by the researcher, which is entitled the equivalent groups of both pre and post-tests design, a matter that made the experimental group apply the experimental method of an independent variable (training strategy by performance modeling of critical swimming speed that uses tempo trainer pro) which is a training strategy the researcher put to achieve a good( 400) m freestyle swimming, getting the way of dividing the regular distance, grouping the level of training capacity to get the best performance of the critical swimming speed to go with Anaerobic threshold speed of each swimmer, decreasing the lost time during that competition, and other training and strategic goals. After that, the researcher interrelated with the Iraqi National Team method of( 400) m freestyle swimming during competition periods so as the experimental group could be applicable for him on his paper achieving days: four days a week and it lasted for six weeks. During that period, the experimental group had done( 24 ) training units that applied the independent variable. A number of scouting experiments were done before the application of the method on the paper target by the support of the assistant team, followed by a number of specialized tests on swimming from various and modern resources which had never been used and applied in our local and regional reality. Therefore, they had been grouped into our local reality through the achieving of the scientific factors. Furthermore, new statistical equations were used to achieve the tests: modeling and critical swimming speed ones. Also, relevant and independent T tests were used to get the experimental outcomes. An imported system (Tempo trainer pro) was also used to help achieving the paper aims together with pulse measuring watch (polar type). The outcomes were furtherly discussed to help the researchers get the following concluding points: - There is a prominent effect of the use of performance modeling in the evolution of the level of tactical performance strategy for swimmers of the experimental group, which caused its superiority over the control group in the achievement variable of freestyle swimming (400) meters. - There is a positive effect of using the water rhythm counter (Tempo Trainer pro) in adjusting the speed parameters according to the appropriate stresses for the training and racing distances until the regularity of the speed and good estimate of the appropriate distance time during the effort of the experimental group swimmers as it was a reason for their superiority over the control group in the dependent search variables.