Critical Swimming Speed Research Articles

Sustained exercise-trained juvenile black carp (Mylopharyngodon piceus) at a moderate water velocity exhibit improved aerobic swimming performance and increased postprandial metabolic responses.

ABSTRACTThe objectives of this study were to examine whether sustained exercise training at four water velocities, i.e. nearly still water (control), 1 body length (BL) s−1, 2 BL s−1 and 4 BL s−1, has effects on swimming performance and digestive metabolism in juvenile black carp (Mylopharyngodon piceus). The results demonstrated that fish subjected to sustained training at 2 and 4 BL s−1 showed significantly higher critical swimming speed (Ucrit) and maximum metabolic rate (MMR) over the control group. Fish subjected to sustained training at 1 and 2 BL s−1 showed a significantly (30 and 54%) prolonged duration, 14 and 17% higher postprandial ṀO2 increment (i.e. ṀO2peak), and 62 and 92% more energy expended on specific dynamic action (SDA), respectively, after consuming a similar meal over fish kept in nearly still water. These results suggest that (1) sustained exercise training at a higher speed (2 or 4 BL s−1) had a positive influence on the aerobic swimming performance of juvenile M. piceus, which may be associated with improved aerobic metabolism; and (2) sustained exercise training at a lower speed (1 or 2 BL s−1) resulted in elevated postprandial metabolic responses in juvenile M. piceus.

Aerobic capacities and swimming performance of polar cod (Boreogadus saida) under ocean acidification and warming conditions.

ABSTRACTPolar cod (Boreogadus saida) is an important prey species in the Arctic ecosystem, yet its habitat is changing rapidly: climate change, through rising seawater temperatures and CO2 concentrations, is projected to be most pronounced in Arctic waters. This study aimed to investigate the influence of ocean acidification and warming on maximum performance parameters of B. saida as indicators for the species' acclimation capacities under environmental conditions projected for the end of this century. After 4 months at four acclimation temperatures (0, 3, 6, 8°C) each combined with two PCO2 levels (390 and 1170 µatm), aerobic capacities and swimming performance of B. saida were recorded following a Ucrit protocol. At both CO2 levels, standard metabolic rate (SMR) was elevated at the highest acclimation temperature indicating thermal limitations. Maximum metabolic rate (MMR) increased continuously with temperature, suggesting an optimum temperature for aerobic scope for exercise (ASex) at 6°C. Aerobic swimming performance (Ugait) increased with acclimation temperature irrespective of CO2 levels, while critical swimming speed (Ucrit) did not reveal any clear trend with temperature. Hypercapnia evoked an increase in MMR (and thereby ASex). However, swimming performance (both Ugait and Ucrit) was impaired under elevated near-future PCO2 conditions, indicating reduced efficiencies of oxygen turnover. The contribution of anaerobic metabolism to swimming performance was very low overall, and further reduced under hypercapnia. Our results revealed high sensitivities of maximum performance parameters (MMR, Ugait, Ucrit) of B. saida to ocean acidification. Impaired swimming capacity under ocean acidification may reflect reduced future competitive strength of B. saida.

Metabolic rates, swimming capabilities, thermal niche and stress response of the lumpfish, Cyclopterus lumpus.

ABSTRACTThe lumpfish (Cyclopterus lumpus) is a semi-pelagic globiform teleost native to the North Atlantic with a ventral suction disc that allows for attachment onto surfaces. Some local populations are in decline and the species has recently become important in salmonid sea cages as cleaner fish. Little is known about the basal physiology of the lumpfish, and a characterization of thermal performance, aerobic capacity, swimming behaviour and stress response is therefore warranted. In the present study, swim tunnel respirometry was performed on lumpfish acclimated to 3, 9 or 15°C. Higher temperatures were also attempted, but at 18°C their behaviour became erratic and 15% of the fish died over 3 weeks of acclimation. Water current tolerance was assessed in two size classes (∼75 g and ∼300 g) both with and without the ability to voluntarily use the ventral suction disc. Lastly, blood samples were taken from resting, exhausted and recovered fish to assess haematological effects of exercise stress. Lumpfish had relatively low aerobic scopes that increased slightly with temperature. Critical swimming speed was poor, increasing within the tested temperatures from 1.3 to 1.7 body lengths s−1 in 300 g fish. They struggled to remain sucked onto surfaces at currents above 70–110 cm s−1, depending on size. Acute stress effects were modest or non-existent in terms of changes in cortisol, lactate, glucose, erythrocytes and ion balance. These results describe a typical sluggish and benthic species, which is contradictory to the pelagic nature of lumpfish in large parts of its lifecycle.

Digestive and locomotor capacity show opposing responses to changing food availability in an ambush predatory fish.

ABSTRACTMetabolic rates vary widely within species, but little is known about how variation in the ‘floor’ [i.e. standard metabolic rate (SMR) in ectotherms] and ‘ceiling’ [maximum metabolic rate (MMR)] for an individual's aerobic scope (AS) are linked with digestive and locomotor function. Any links among metabolic traits and aspects of physiological performance may also be modulated by fluctuations in food availability. This study followed changes in SMR, MMR, and digestive and locomotor capacity in southern catfish (Silurus meridionalis) throughout 15 days of food deprivation and 15 days of refeeding. Individuals downregulated SMR during food deprivation and showed only a 10% body mass decrease during this time. Whereas critical swim speed (Ucrit) was robust to food deprivation, digestive function decreased after fasting with a reduced peak oxygen uptake during specific dynamic action (SDA) and prolonged SDA duration. During refeeding, individuals displayed rapid growth and digestive function recovered to pre-fasting levels. However, refed fish showed a lower Ucrit than would be expected for their increased body length and in comparison to measures at the start of the study. Reduced swimming ability may be a consequence of compensatory growth: growth rate was negatively correlated with changes in Ucrit during refeeding. Southern catfish downregulate digestive function to reduce energy expenditure during food deprivation, but regain digestive capacity during refeeding, potentially at the cost of decreased swimming performance. The plasticity of maintenance requirements suggests that SMR is a key fitness trait for in this ambush predator. Shifts in trait correlations with food availability suggest that the potential for correlated selection may depend on context.

Larval swimming capacities affect genetic differentiation and range size in demersal marine fishes

Dispersal is a fundamental process governing the ecological and evolutionary dynamics of any given species. Due to inherent challenges associated with measuring dispersal directly, identifying proxies for dispersal capacity has long been an active field of research across ecosystems. In marine systems, pelagic larval duration (PLD) has been one of the most widely used indicators of interspecific dispersal potential. The validity of this proxy, however, relies mostly on the assumption of entirely passive dispersal, a notion that has been challenged by findings of strong larval behavioural capabilities. Here, we assessed the effect of larval swimming capacities measured as mean critical swimming speed (U-crit) on emergent species-level properties related to dispersal potential, population genetic structure and global range size, in demersal marine fishes. In a meta-analytic framework, we tested the relative importance of U-crit versus other intrinsic (PLD, egg type, adult body size) and extrinsic (genetic marker type, study scale) predictors of isolation-by-distance slope, global FST and range size. U-crit showed stronger relationships with all emergent response variables than PLD and was consistently the most important predictor in multi-model inference. Our findings indicate that larval swimming capacities could serve as a powerful indicator of a species’ long-distance dispersal potential.

Selection on the morphology-physiology-performance nexus: Lessons from freshwater stickleback morphs.

Conspecifics inhabiting divergent environments frequently differ in morphology, physiology, and performance, but the interrelationships amongst traits and with Darwinian fitness remains poorly understood. We investigated population differentiation in morphology, metabolic rate, and swimming performance in three‐spined sticklebacks (Gasterosteus aculeatus L.), contrasting a marine/ancestral population with two distinct freshwater morphotypes derived from it: the “typical” low‐plated morph, and a unique “small‐plated” morph. We test the hypothesis that similar to plate loss in other freshwater populations, reduction in lateral plate size also evolved in response to selection. Additionally, we test how morphology, physiology, and performance have evolved in concert as a response to differences in selection between marine and freshwater environments. We raised pure‐bred second‐generation fish originating from three populations and quantified their lateral plate coverage, burst‐ and critical swimming speeds, as well as standard and active metabolic rates. Using a multivariate Q ST‐F ST framework, we detected signals of directional selection on metabolic physiology and lateral plate coverage, notably demonstrating that selection is responsible for the reduction in lateral plate coverage in a small‐plated stickleback population. We also uncovered signals of multivariate selection amongst all bivariate trait combinations except the two metrics of swimming performance. Divergence between the freshwater and marine populations exceeded neutral expectation in morphology and in most physiological and performance traits, indicating that adaptation to freshwater habitats has occurred, but through different combinations of traits in different populations. These results highlight both the complex interplay between morphology, physiology and performance in local adaptation, and a framework for their investigation.

How the expression of green fluorescent protein and human cardiac actin in the heart influences cardiac function and aerobic performance in zebrafish Danio rerio.

The present study examined how the expression of enhanced green fluorescent protein (eGFP) and human cardiac actin (ACTC) in zebrafish Danio rerio influences embryonic heart rate (RH ) and the swim performance and metabolic rate of adult fish. Experiments with the adults involved determining the critical swimming speed (Ucrit , the highest speed sustainable and measure of aerobic capacity) while measuring oxygen consumption. Two different transgenic D. rerio lines were examined: one expressed eGFP in the heart (tg(cmlc:egfp)), while the second expressed ACTC in the heart and eGFP throughout the body (tg(cmlc:actc,ba:egfp)). It was found that RH was significantly lower in the tg(cmlc:actc,ba:egfp) embryos 4 days post-fertilization compared to wild-type (WT) and tg(cmlc:egfp). The swim experiments demonstrated that there was no significant difference in Ucrit between the transgenic lines and the wild-type fish, but metabolic rate and cost of transport (oxygen used to travel a set distance) was nearly two-fold higher in the tg(cmlc:actc,ba:egfp) fish compared to WT at their respective Ucrit . These results suggest that the expression of ACTC in the D. rerio heart and the expression of eGFP throughout the animal, alters cardiac function in the embryo and reduces the aerobic efficiency of the animal at high levels of activity.

Measuring Ucrit and endurance: equipment choice influences estimates of fish swimming performance.

This study compared the critical swimming speed (Ucrit ) and endurance performance of three Australian freshwater fish species in different swim-test apparatus. Estimates of Ucrit measured in a large recirculating flume were greater for all species compared with estimates from a smaller model of the same recirculating flume. Large differences were also observed for estimates of endurance swimming performance between these recirculating flumes and a free-surface swim tunnel. Differences in estimates of performance may be attributable to variation in flow conditions within different types of swim chambers. Variation in estimates of swimming performance between different types of flumes complicates the application of laboratory-based measures to the design of fish passage infrastructure.

High postural costs and anaerobic metabolism during swimming support the hypothesis of a U-shaped metabolism–speed curve in fishes

Swimming performance is considered a key trait determining the ability of fish to survive. Hydrodynamic theory predicts that the energetic costs required for fishes to swim should vary with speed according to a U-shaped curve, with an expected energetic minimum at intermediate cruising speeds and increasing expenditure at low and high speeds. However, to date no complete datasets have shown an energetic minimum for swimming fish at intermediate speeds rather than low speeds. To address this knowledge gap, we used a negatively buoyant fish, the clearnose skate Raja eglanteria, and took two approaches: a classic critical swimming speed protocol and a single-speed exercise and recovery procedure. We found an anaerobic component at each velocity tested. The two approaches showed U-shaped, though significantly different, speed-metabolic relationships. These results suggest that (i) postural costs, especially at low speeds, may result in J- or U-shaped metabolism-speed curves; (ii) anaerobic metabolism is involved at all swimming speeds in the clearnose skate; and (iii) critical swimming protocols might misrepresent the true costs of locomotion across speeds, at least in negatively buoyant fish.

The gill parasite Paramoeba perurans compromises aerobic scope, swimming capacity and ion balance in Atlantic salmon.

The parasitic amoeba Paramoeba perurans is an aetiological agent of amoebic gill disease (AGD), a serious problem in seawater salmonid aquaculture globally. Other finfish species are also infected and infection events may be associated with periods of unusual high temperatures. Currently little is known about the impact of AGD on wild fish, but in a time with global warming and increasing aquaculture production this potential threat could be on the rise. A better understanding of the pathophysiology of infected fish is therefore warranted. In this study, groups of Atlantic salmon with and without AGD were tested in a large swim tunnel respirometer in seawater at 13°C to assess oxygen uptake, swimming capacity and blood parameters. Standard metabolic rates were similar between groups, but the maximum rate of oxygen uptake was drastically reduced in infected fish, which resulted in a smaller aerobic scope (AS) of 203 mg O2 kg-1 h-1 compared to 406 mg O2 kg-1 h-1 in healthy fish. The critical swimming speed was 2.5 body lengths s-1 in infected fish and 3.0 body lengths s-1 in healthy ones. Furthermore, AGD fish had lower haematocrit and [haemoglobin], but similar condition factor compared to healthy fish. Prior to swim trials infected fish had higher plasma osmolality, elevated plasma [Na+], [Cl-] and [cortisol], indicating reduced capacity to maintain ionic homoeostasis as well as chronic stress during routine conditions. These results demonstrate that AGD compromises gill function both in terms of gas exchange and ion regulation, and consequently the capacity for aerobic activity is reduced. Reduced AS due to the P. perurans infections is likely to interfere with appetite, growth and overall survival, even more so in the context of a warmer and more hypoxic future.

Effects of acute temperature and salinity changes, body length and starvation on the critical swimming speed of juvenile tiger puffer, Takifugu rubripes.

The critical swimming speed (U crit, cms-1) of juvenile tiger puffer Takifugu rubripes was determined under different temperatures (15, 21, 25 and 30°C), salinities (5, 10, 20, 32 and 40), body lengths (3.32, 4.08, 5.06 and 5.74cm) and starvation days (1, 3, 6 and 9days). Acute temperature change, body length and starvation significantly influenced the U crit of tiger puffers, whereas acute salinity change had no significant effect. The U crit increased as the temperature increased from 15 to 30°C. The U crit increased as the body length increased from 3.32 to 5.74cm, whereas relative critical swimming speed (U crit', body lengths-1) decreased. The relationship between the body length (l, cm) and U crit or U crit' can be described by the quadratic model as U crit=-1.4088l 2+16.976l-11.64, R 2=0.9698 (P<0.01) or U crit'=-0.1937l 2+0.9504l+7.7666, R 2=0.9493 (P<0.01). The U crit decreased as starvation days increased from 1 to 9days. Low temperature and starvation can reduce the swimming ability of juvenile tiger puffers. Results can be of value in evaluating the swimming ability of juvenile tiger puffers, understanding ecological processes and improving the population enhancement of tiger puffers.

Recovery from exhaustive swimming and its effect on fillet quality in haddock (Melanogrammus aeglefinus)

Abstract Wild haddock (Melanogrammus aeglefinus) of commercial size (0.8–2.49 kg, 45–60 cm) were swum to exhaustion in a large swim tunnel and then allowed to recuperate for 0, 3 or 6 h, to investigate the effects of exhaustive swimming on blood glucose, blood lactate and post mortem development of fillet quality. There was a positive linear relationship between critical (aerobic) swimming speed (Ucrit) and body length (BL). The average Ucrit was 1.25 ± 0.29 (SD) BL s−1, which is close to that reported by others for haddock. Swimming to exhaustion resulted in reduced time to reach maximum muscle stiffness of the fillet (no recuperation vs unswum control), but the effect was remedied by recuperation for 3 h or more. Blood glucose and blood lactate increased during exercise and remained elevated throughout the entire 6-h resting period, indicating that complete recovery of these parameters may take more than 6 h. There was no significant effect of exhaustive swimming on muscle pH or colouration of the fillet. Taken together, the data suggest that swimming to exhaustion may have moderate and reversible negative effects on fillet quality in haddock. The effects observed in the present study are consistent with a recent study on exhaustive swimming in Atlantic cod, but less severe than that reported for haddock caught by trawl. This suggests that other factors (e.g. crowding/packing in the codend, barotrauma or suffocation) are contributing to the deterioration of fillet quality seen frequently in haddock caught by trawl.

Swimming abilities of juvenile estuarine fishes: implications for passage at water control structures

The capability of early life history stage fishes to access nursery habitat within managed salt marshes is dependent on their ability to negotiate water control structures (WCSs). Knowledge of swimming ability and hydrodynamic preferences is essential to assess the impact of WCSs on fish movement in managed marshes. These data, however, are lacking for many common estuarine fishes, and the utility of the data for the few species examined thus far is limited. We examined critical swimming speeds and derived linear relationships between fish size and swimming speed for juveniles of six common estuarine fish species of the southeast U.S. and northern Gulf of Mexico coasts. White mullet Mugil curema displayed the greatest swimming ability among these six species and was able to swim against currents ≥ 30 cm s−1 higher than the other species examined at the same size. The remaining species displayed lower critical swimming speeds and were classified into groups of moderate (pinfish Lagodon rhomboides, striped mullet Mugil cephalus) or slow (silver perch Bairdiella chrysoura, spotfin mojarra Eucinostomus argenteus, spot Leiostomus xanthurus) swimmers. Our results suggest that high-flow conditions at WCSs would likely preclude the passage of all but the largest juvenile fishes, and passage for most juveniles would occur under low-flow conditions; these flows at WCSs are dictated largely by site-specific tidal and weather conditions.

Cardio-respiratory function during exercise in the cobia, Rachycentron canadum: The impact of crude oil exposure

Aerobic exercise capacity is dependent on the cardiorespiratory system's ability to supply oxygen at a rate that meets energetic demands. In teleost fish crude oil exposure, with the associated polycyclic aromatic hydrocarbons (PAH's), reduces exercise performance and this has been hypothesized to be due to compromised cardiovascular function. In this study, we test this hypothesis by simultaneously measuring cardiovascular performance, oxygen consumption, and swim performance in a pelagic teleost, the cobia (Rachycentron canadum). Metabolic rate increased over 300% in both groups during the swim trial but as the fish approached the critical swim speed (Ucrit) MO2 was 12% lower in the oil exposed fish. Further, stroke volume was initially 35% lower while heart rate was 15% higher in the oil exposed compared to control fish. Our findings suggested, while aspects of cardiovascular and metabolic function are altered by oil exposure, additional studies are needed to further understand the homeostatic mechanisms that may sustain cardiovascular function at higher exercise intensities in cobia.

THE EFFECTS OF DIFFERENT DOSES OF COPPER SULPHATE PENTAHYDRATE (CuSO4.5H2O) ON CRITICAL SWIMMING SPEED AND HAEMATOLOGY PARAMETERS OF RAINBOW TROUT (Oncorhynchus mykiss)

In this study were researched the effects of the two different dosage application of copper sulphate pentahydrate (CuSO 4 .5H 2 O) pesticide and rainbow trout ( Oncorhynchus mykiss ) was used as the material. As a result of the application period, control and application groups critical swimming speed and blood parameters were investigated. In the rainbow trout, exposed to different doses of the copper sulphate penta hydrate (CuSO 4 .5H 2 O) pesticide, critical swimming speed was investigated and the effects was found to be significant (p 0.05). The hemoglobin value was significantly effected by treatment x day interaction (p 0.05).

Are fancy guppies (&lt;em&gt;Poeciliareticulata&lt;/em&gt; Peters, 1859) invasive?

Guppies (Poecilia reticulata Peters 1859) have been introduced to Sri Lanka in the early 1970s to combat the menace of Malaria. Due to their rapid range expansion in natural waterways, guppies are labeled as an ‘invasive species.’ Guppies are also popular in the ornamental fish trade where a wide variety of ornamental guppy varieties with attractive colour and fin patterns have been produced through selective breeding; they are commonly known as ‘fancy guppies’ or ‘saree guppies’. Since there are some concerns over the invasiveness of these fancy guppies into natural water bodies in Sri Lanka, the potential invasiveness of two common fancy guppy varieties with long caudal fins viz. black guppies and yellow guppies, was assessed under laboratory conditions using their specific growth rates (SGR) and critical swimming speeds (Ucrit). Results in the present study showed that the SGR of black guppies (1.0 % g day-1), and yellow guppies (0.99 % g day-1) were significantly lower (p &lt; 0.05) than that of the wild guppies (1.31% g day-1). Further, the Ucrit of the black guppies (23.8 cm s-1), and yellow guppies (26.8 cm s-1) were significantly lower (p &lt; 0.05) than that of the wild guppies (28.8 cm s-1). Since the long caudal fins significantly reduced the swimming speed (p &lt; 0.05: ANOVA) and hence the SGR of the two fancy guppy varieties, there is strong evidence for an inter-variety competition to occur among the wild and fancy guppies where the latter would be competitively eliminated by the wild guppies in terms of competition owing to their short tail. Therefore, the long caudal fin is a predicament to fancy guppies for both swimming and securing food in the water column. This study also challenges some views of all guppies being categorized as ‘invasive’ and demonstrated that the fancy guppies are unable to compete with their wild counterparts but are confined to ornamental displays in places such as indoor and outdoor fish tanks.

Later life swimming performance and persistent heart damage following subteratogenic PAH mixture exposure in the Atlantic killifish (Fundulus heteroclitus).

High-level, acute exposures to individual polycyclic aromatic hydrocarbons (PAHs) and complex PAH mixtures result in cardiac abnormalities in developing fish embryos. Whereas acute PAH exposures can be developmentally lethal, little is known about the later life consequences of early life, lower level PAH exposures in survivors. A population of PAH-adapted Fundulus heteroclitus from the PAH-contaminated Superfund site, Atlantic Wood Industries, Elizabeth River, Portsmouth, Virginia, United States, is highly resistant to acute PAH cardiac teratogenicity. We sought to determine and characterize long-term swimming performance and cardiac histological alterations of a subteratogenic PAH mixture exposure in both reference killifish and PAH-adapted Atlantic Wood killifish embryos. Killifish from a relatively uncontaminated reference site, King's Creek, Virginia, United States, and Atlantic Wood killifish were treated with dilutions of Elizabeth River sediment extract at 24 h post fertilization (hpf). Two proven subteratogenic dilutions, 0.1 and 1.0% Elizabeth River sediment extract (total PAH 5.04 and 50.4 µg/L, respectively), were used for embryo exposures. Then, at 5-mo post hatching, killifish were subjected to a swim performance test. A separate subset of these individuals was processed for cardiac histological analysis. Unexposed King's Creek killifish significantly outperformed the unexposed Atlantic Wood killifish in swimming performance as measured by Ucrit (i.e., critical swimming speed). However, King's Creek killifish exposed to Elizabeth River sediment extract (both 0.1 and 1.0%) showed significant declines in Ucrit. Histological analysis revealed the presence of blood in the pericardium of King's Creek killifish. Although Atlantic Wood killifish showed baseline performance deficits relative to King's Creek killifish, their pericardial cavities were nearly free of blood and atrial and ventricular alterations. These findings may explain, in part, the diminished swimming performance of King's Creek fish. Environ Toxicol Chem 2017;36:3246-3253. © 2017 SETAC.

Swimming and Recovery Abilities of Juvenile Chinese Sturgeon Acipenser sinensis

AbstractBreeding populations of the Chinese Sturgeon Acipenser sinensis are endemic to the Yangtze River in China, but other wild populations have been extirpated, and the species is critically endangered. The swimming performance of juvenile Chinese Sturgeon was tested in a flume‐type respirometer using a three‐phase test: a constant velocity endurance test, followed by a 30‐min recovery period, and then a stepped velocity test to determine the critical swimming speed (Ucrit). Swimming endurance (at 19 ± 1°C) was tested at five constant speeds: 3.0, 3.5, 4.0, 4.5, and 5.0 body lengths per second (BL/s) (groups 1–5). A control group (group 0) was used to determine Ucrit for fish that had not been subjected to the endurance test. The Ucrit of the control group (U′) was 4.32 ± 0.30 BL/s (mean ± SE) and after fish had completed the endurance test the Ucrit ranged from 2.88 ± 0.15 BL/s in group 1 to 3.64 ± 0.28 BL/s in group 5, with corresponding recovery ratios (Ucrit/U′) of 66.7 ± 3.4% and 84.3 ± 6.4%. Endurance time decreases with swimming speed, so these results indicate that fatigue resulting from swimming at low speed for a longer time requires more recovery time than does fatigue resulting from swimming at high speed for a shorter time. The relationship between swimming speed (U; BL/s) and endurance time (te; min) is described by logte = 3.90 – 0.64U (r2 = 0.769, P &lt; 0.05).

Swimming speeds of Mediterranean settlement‐stage fish larvae nuance Hjort's aberrant drift hypothesis

AbstractHistorically, the mortality of early‐life stages of marine fishes was supposed to be mostly caused by poor feeding during a critical period and aberrant drifting away from favorable recruitment areas. While fish larvae may display remarkable swimming abilities, Hjort's aberrant drift hypothesis has rarely been tested. In this study, we measured critical swimming speed (Ucrit) of settlement‐stage larvae of six coastal, warm temperate Mediterranean fish species, for which no data were previously available (Sparidae: Boops boops, Diplodus annularis, Spicara smaris, Spondyliosoma cantharus; Pomacentridae: Chromis chromis; Mugilidae sp.). Their swimming speeds were comparable with those of other temperate species, but also with the speeds of tropical species, which are considered as very fast swimmers. Mugilidae were the fastest (29.2 cm s−1), followed by Pomacentridae (22.8 cm s−1) and Sparidae (11.6 cm s−1). Most larvae swam in an inertial regime (Reynolds number &gt; 1000). Those swimming speeds were then implemented in a Lagrangian model of the competency period of these species, set in the same area (the Ligurian Sea) and at the same time (June 2014) as the observations. In this modeling experiment, directional swimming strongly increased the proportion of successful settlers, independent of mesoscale hydrological structures. Fish larvae could settle on the coast from as far as tens of kilometers offshore, in just 4 d. These findings suggest that aberrant drift is unlikely to occur for strong swimming temperate larvae and show that larval behavior should be considered on equal footing with ocean currents when assessing larval fish dispersal.

Swimming Performance of Rock Carp Procypris rabaudi and Prenant's Schizothoracin Schizothorax prenanti Acclimated to Total Dissolved Gas Supersaturated Water

AbstractTotal dissolved gas (TDG) supersaturation is becoming an increasingly serious problem in the upper Yangtze River basin and has been identified as a potentially negative environmental effect of hydropower development and operations. Juvenile Rock Carp Procypris rabaudi and Prenant's Schizothoracin Schizothorax prenanti dwell in the upper reaches of the Yangtze River and were selected as experimental fish to evaluate the impact of TDG supersaturation on swimming performance. The results showed that the swimming speeds of Rock Carp and Prenant's Schizothoracin differed significantly under different exposure times to TDG‐supersaturated water (129–131%). Exposure of fish to supersaturated TDG for 2 and 4 h with no recovery resulted in significantly lower critical swimming (Ucrit) and burst swimming (Uburst) speeds compared with those of fish not exposed to supersaturated TDG. The Ucrit and Uburst values for Rock Carp not exposed to supersaturated TDG were 1.4–1.6 times higher than those of fish exposed to supersaturated TDG for 2 h and 1.9–2.0 times higher than those of fish exposed for 4 h. Similarly, the Ucrit and Uburst values for Prenant's Schizothoracin not exposed to supersaturated TDG were 1.4–1.8 times higher than those of fish exposed to supersaturated TDG for 2 h and 2.5–3.1 times higher than those of fish exposed for 4 h. Fish that were exposed to supersaturated TDG for 2 and 4 h and then allowed to recover for 2 d swam better than fish exposed to supersaturated TDG for the same amount of time without recovery. Although a 2‐d recovery improved swimming performance over that of fish not allowed to recover, only the Rock Carp (and not the Prenant's Schizothoracin) returned to the swimming speeds observed in the control fish not exposed to supersaturated TDG. The results of our research can be applied to the operation of hydropower stations and can contribute fundamental data for establishing water‐related environmental standards in China.Received December 4, 2016; accepted July 1, 2017 Published online October 11, 2017