Swimming Kinematics Research Articles

Persistent Hydrodynamic Cues Elicit Orientation-Specific Behavioral Sensitivities and Kinematic Responses in Dispersed Crab Larvae

The estuarine mud crab Panopeus herbstii navigates a complex, but structured, hydrodynamic environment throughout its life history. The effects of hydrodynamic cues associated with turbulent flows on larval behavior are relatively well understood in the context of selective tidal stream transport (STST) phenomena during the dispersed (pelagic) larval stages preceding benthic settlement. In contrast, the potential relevance of hydrodynamic cues associated with spatiotemporally persistent flow features, which are typical of estuarine regions of enhanced productivity such as fronts and clines, remains much less certain. To investigate the behavioral relevance of persistent hydrodynamic cues, larval assays were conducted in a flume system that uses a laminar slot jet to produce steady fluid shear layers. Further, to ascertain whether or not the spatial orientation of the shear layers relative to gravity significantly affected larval behavior, assays were conducted in upwelling, downwelling, and horizontal shear flows, corresponding to the direction of the bulk flow produced by the jet. The flow was quantified using particle image velocimetry (PIV) and tuned to produce ecologically-relevant hydrodynamic conditions for larval assays. Changes in larval swimming kinematics show a distinct response to shear flows in all orientations relative to no-flow conditions, and the macro effect of these changes is to enhance depth-keeping and induce area-restricted search behaviors. Furthermore, the specifics of larval behavioral responses depend on the directional orientation of the shear flow, and the statistical properties of the strength of the hydrodynamic cue (vorticity) eliciting these responses are also shown to be shear flow orientation-specific. Orientation-specific hydrodynamic sensitivity and behavioral response strategies in the presence of persistent hydrodynamic cues may enable larvae to effectively forage and sample to locate and exploit nearby resource patches, while also inducing dispersal trajectories towards favorable benthic settlement habitats through depth regulation and effective STST. In this regard, hydrodynamic cues associated with spatiotemporally persistent flow features are likely fundamental drivers of decapod crab larvae behavior and may act as another mechanism of larval patchiness by directly impacting finescale population distributions and resultant dispersal trajectories.

Swimming with swirl in a viscoelastic fluid

Abstract

Reef-associated fishes have more maneuverable body shapes at a macroevolutionary scale

Marine habitats vary widely in structure, from incredibly complex coral reefs to simpler deep water and open ocean habitats. Hydromechanical models of swimming kinematics and microevolutionary studies suggest that these habitats select for different body shape characteristics. Fishes living in simple habitats are predicted to experience selection for energy-efficient sustained swimming, which can be achieved by fusiform body shapes. In contrast, fishes living in complex habitats are predicted to be under selection for maneuverability, which can be enhanced by deep-bodied and laterally compressed forms. To look for a signature of these processes at a broad macroevolutionary scale, we quantified the body shapes of 3322 species of marine teleostean fishes using a series of linear measurements. We scored each species for whether they were reef-associated or not and tested for morphological differences using a phylogenetic framework. Our results confirmed significant overall shape differences between reef-associated teleosts and those occupying structurally simpler marine habitats. Reef-associated species have, on average, deeper bodies and higher depth-to-width ratios, while non-reef species are more streamlined with narrower and shallower caudal peduncles. Despite the numerous evolutionary forces that may influence body shapes on a broad macroevolutionary scale, our results reveal differences in body shapes between reef-associated and non-reef species that are consistent with hydromechanical models of swimming kinematics as well as with microevolutionary patterns.

Slender phoretic theory of chemically active filaments

Artificial microswimmers, or ‘microbots’, have the potential to revolutionise non-invasive medicine and microfluidics. Microbots that are powered by self-phoretic mechanisms, such as Janus particles, often harness a solute fuel in their environment. Traditionally, self-phoretic particles are point like, but slender phoretic rods have become an increasingly prevalent design. While there has been substantial interest in creating efficient asymptotic theories for slender phoretic rods, hitherto such theories have been restricted to straight rods with axisymmetric patterning. However, modern manufacturing methods will soon allow fabrication of slender phoretic filaments with complex three-dimensional shapes. In this paper, we develop a slender body theory for the solute of self-diffusiophoretic filaments of arbitrary three-dimensional shape and patterning. We demonstrate analytically that, unlike other slender body theories, first-order azimuthal variations arising from curvature and confinement can make a leading-order contribution to the swimming kinematics.

Fish-like aquatic propulsion studied using a pneumatically-actuated soft-robotic model

Fish locomotion is characterized by waves of muscle electrical activity that proceed from head to tail, and result in an undulatory pattern of body bending that generates thrust during locomotion. Isolating the effects of parameters like body stiffness, co-activation between the right and left sides of the body, and frequency on thrust generation has proven to be difficult in live fishes. We use a pneumatically-actuated fish-like model to investigate how these parameters affect locomotor force generation. We measure thrust as well as side forces and torques generated during propulsion. Using a statistical linear model we examine the effects of input parameter combinations on thrust generation. We show that both stiffness and frequency substantially affect swimming kinematics, and that there are complex interactive effects of these two parameters on thrust. The stiffer the backbone the more impact that increasing frequency has on thrust production. For stiffer models, increasing frequency resulted in higher values for both thrust and lateral forces. Large side forces reduce swimming efficiency but this effect could be mitigated by decreasing undulatory wavelength and allowing appropriate phasing of left and right body movements to reduce amplitudes of side force.

Fibrous Flagellar Hairs of Chlamydomonas reinhardtii Do Not Enhance Swimming

The flagella of Chlamydomonas reinhardtii possess fibrous ultrastructures of a nanometer-scale thickness known as mastigonemes. These structures have been widely hypothesized to enhance flagellar thrust; however, detailed hydrodynamic analysis supporting this claim is lacking. In this study, we present a comprehensive investigation into the hydrodynamic effects of mastigonemes using a genetically modified mutant lacking the fibrous structures. Through high-speed observations of freely swimming cells, we found the average and maximum swimming speeds to be unaffected by the presence of mastigonemes. In addition to swimming speeds, no significant difference was found for flagellar gait kinematics. After our observations of swimming kinematics, we present direct measurements of the hydrodynamic forces generated by flagella with and without mastigonemes. These measurements were conducted using optical tweezers, which enabled high temporal and spatial resolution of hydrodynamic forces. Through our measurements, we found no significant difference in propulsive flows due to the presence of mastigonemes. Direct comparison between measurements and fluid mechanical modeling revealed that swimming hydrodynamics were accurately captured without including mastigonemes on the modeled swimmer’s flagella. Therefore, mastigonemes do not appear to increase the flagella’s effective area while swimming, as previously thought. Our results refute the longstanding claim that mastigonemes enhance flagellar thrust in C. reinhardtii, and so, their function still remains enigmatic.

The "dog paddle": Stereotypic swimming gait pattern in different dog breeds.

The term "dog paddle" has been applied to the swimming behavior of various terrestrial and aquatic species. Dog paddling refers to a form of drag-based, paddle propulsion in which the limbs are oriented underneath the body and moved through an arc. Despite the ubiquity of the term, there has been no analysis of the swimming kinematics of dogs. Underwater video was recorded of surface swimming dogs (velocity: 0.4-1.1 m/s) for eight individuals from six breeds, ranging in size from Yorkshire Terrier (3.6 kg) to Newfoundland dog (63.5 kg). The quadrupedal paddling stroke was analyzed to determine kinematics and coordination of the limbs. The paddling stroke represented a modified terrestrial gait, which was outside typical gaits for terrestrial locomotion by dogs. Stroke frequency decreased with increasing body size. The stroke cycle consisted of power and recovery phases. During the power phase, digits of the paw were abducted and the forelimb was swept posteriorly until perpendicular to the body. In the recovery phase, digits were adducted while the brachium was retracted anteriorly and the manus supinated. The power phase was about 34% of stroke cycle and shorter than the recovery phase for both fore and hindlimbs. Maximum velocity during the power phase was greater than the recovery phase. The modified terrestrial gait used for swimming by dogs appears to be stereotypic among breeds, whereas terrestrial locomotion in dogs shows substantial variation in gait. Without constraints imposed by gravity and substrate contact, swimming dogs can utilize a gait profile different from terrestrial gaits. SUMMARY STATEMENT: Despite the ubiquity of the term "dog paddle" to describe the swimming motions of animals, this is the first time that the swimming motions of dogs have been analyzed.

Neuromodulatory Selection of Motor Neuron Recruitment Patterns in a Visuomotor Behavior Increases Speed.

Animals generate locomotion at different speeds to suit their behavioral needs. Spinal circuits generate locomotion at these varying speeds by sequential activation of different spinal interneurons and motor neurons. Larval zebrafish can generate slow swims for prey capture and exploration by activation of secondary motor neurons and much faster and vigorous swims during escape and struggle via additional activation of primary motor neurons. Neuromodulators are known to alter the motor output of spinal circuits, but their precise role in speed regulation is not wellunderstood. Here, in the context of optomotor response (OMR), an innate evoked locomotor behavior, we show that dopamine (DA) provides an additional layer to regulation of swim speed in larval zebrafish. Activation of D1-like receptors increases swim speed during OMR in free-swimming larvae. By analyzing tail bend kinematics in head-restrained larvae, we show that the increase in speed is actuated by larger tail bends. Whole-cell patch-clamp recordings from motor neurons reveal that, during OMR, typically only secondary motor neurons are active, whereas primary motor neurons are quiescent. Activation of D1-like receptors increases intrinsic excitability and excitatory synaptic drive in primary and secondary motor neurons. These actions result in greater recruitment of motor neurons during OMR. Our findings provide an example of neuromodulatory reconfiguration of spinal motor neuron speed modules where members are selectively recruited and motor drive is increased to effect changes in locomotor speed. VIDEO ABSTRACT.

Quantification of the influence of drugs on zebrafish larvae swimming kinematics and energetics.

The use of zebrafish larvae has aroused wide interest in the medical field for its potential role in the development of new therapies. The larvae grow extremely quickly and the embryos are nearly transparent which allows easy examination of its internal structures using fluorescent imaging techniques. Medical treatment of zebrafish larvae can directly influence its swimming behaviours. These behaviour changes are related to functional changes of central nervous system and transformations of the zebrafish body such as muscle mechanical power and force variation, which cannot be measured directly by pure experiment observation. To quantify the influence of drugs on zebrafish larvae swimming behaviours and energetics, we have developed a novel methodology to exploit intravital changes based on observed zebrafish locomotion. Specifically, by using an in-house MATLAB code to process the recorded live zebrafish swimming video, the kinematic locomotion equation of a 3D zebrafish larvae was obtained, and a customised Computational Fluid Dynamics tool was used to solve the fluid flow around the fish model which was geometrically the same as experimentally tested zebrafish. The developed methodology was firstly verified against experiment, and further applied to quantify the fish internal body force, torque and power consumption associated with a group of normal zebrafish larvae vs. those immersed in acetic acid and two neuroactive drugs. As indicated by our results, zebrafish larvae immersed in 0.01% acetic acid display approximately 30% higher hydrodynamic power and 10% higher cost of transport than control group. In addition, 500 μM diphenylhydantoin significantly decreases the locomotion activity for approximately 50% lower hydrodynamic power, whereas 100 mg/L yohimbine has not caused any significant influences on 5 dpf zebrafish larvae locomotion. The approach has potential to evaluate the influence of drugs on the aquatic animal’s behaviour changes and thus support the development of new analgesic and neuroactive drugs.

Response of the copepod Acartia tonsa to the hydrodynamic cues of small-scale, dissipative eddies in turbulence.

This study quantifies the behavioral response of a marine copepod (Acartia tonsa) to individual, small-scale, dissipative vortices that are ubiquitous in turbulence. Vortex structures were created in the laboratory using a physical model of a Burgers vortex with characteristics corresponding to typical dissipative vortices that copepods are likely to encounter in the turbulent cascade. To examine the directional response of copepods, vortices were generated with the vortex axis aligned in either the horizontal or vertical direction. Tomographic particle image velocimetry was used to measure the volumetric velocity field of the vortex. Three-dimensional copepod trajectories were digitally reconstructed and overlaid on the vortex flow field to quantify A. tonsa's swimming kinematics relative to the velocity field and to provide insight into the copepod behavioral response to hydrodynamic cues. The data show significant changes in swimming kinematics and an increase in relative swimming velocity and hop frequency with increasing vortex strength. Furthermore, in moderate-to-strong vortices, A. tonsa moved at elevated speed in the same direction as the swirling flow and followed spiral trajectories around the vortex, which would retain the copepod within the feature and increase encounter rates with other similarly behaving Acartia While changes in swimming kinematics depended on vortex intensity, orientation of the vortex axis showed minimal significant effect. Hop and escape jump densities were largest in the vortex core, which is spatially coincident with the peak in vorticity, suggesting that vorticity is the hydrodynamic cue that evokes these behaviors.

Extreme temperature combined with hypoxia, affects swimming performance in brown trout (Salmo trutta).

Climate change is predicted to impact freshwater aquatic environments through changes to water temperature (Twater), river flow and eutrophication. Riverine habitats contain many economically and ecologically important fishes. One such group is the migratory salmonids, which are sensitive to warm Twater and low O2 (hypoxia). While several studies have investigated the independent effects of Twater and hypoxia on fish physiology, the combined effects of these stressors is less well known. Furthermore, no study has investigated the effects of Twater and O2 saturation levels within the range currently experienced by a salmonid species. Thus, the aim of this study was to investigate the simultaneous effects of Twater and O2 saturation level on the energetics and kinematics of steady-state swimming in brown trout, Salmo trutta. No effect of O2 saturation level (70 and 100% air saturation) on tail-beat kinematics was detected. Conversely, Twater (10, 14, 18 and 22°C) did affect tail-beat kinematics, but a trade-off between frequency (ftail) and amplitude (A, maximum tail excursion) maintained the Strouhal number (St = ftail• A/U, where U is swimming speed) within the theoretically most mechanically efficient range. Swimming oxygen consumption rate (n}{}{dot{M}}_{{mathsf{O}}_{mathsf{2}}}) and cost of transport increased with both U and Twater. The only effect of O2 saturation level was observed at the highest Twater (22°C) and fastest swimming speed (two speeds were used—0.6 and 0.8 m s−1). As the extremes of this study are consistent with current summer conditions in parts of UK waterways, our findings may indicate that S. trutta will be negatively impacted by the increased Twater and reduced O2 levels likely presented by anthropogenic climate change.

Evolution of Feeding Shapes Swimming Kinematics of Barnacle Naupliar Larvae: A Comparison between Trophic Modes.

SynopsisA central goal in evolutionary biology is connecting morphological features with ecological functions. For marine invertebrate larvae, appendage movement determines locomotion, feeding, and predator avoidance ability. Barnacle larvae are morphologically diverse, and the morphology of non-feeding lecithotrophic nauplii are distinct from those that are planktotrophic. Lecithotrophic larvae have a more globular body shape and simplified appendages when compared with planktotrophs. However, little is known about whether and how such morphological changes affect kinematics, hydrodynamics, and ecological functions. Here, we compared the nauplii kinematics and hydrodynamics of a lecithotrophic Rhizocephalan species, Polyascus planus, against that of the planktotrophic nauplii of an intertidal barnacle, Tetraclita japonica. High-speed, micro-particle image velocimetry analysis showed that the Polyascus nauplii swam faster and had higher amplitude and more synchronous appendage beating than the Tetraclita nauplii. This fast swimming was accompanied by a faster attenuation of induced flow with distance, suggesting reduced predation risk. Tetraclita nauplii had more efficient per beat cycles with less backward displacement during the recovery stroke. This “anchoring effect” resulted from the anti-phase beating of appendages. This movement, together with a high-drag body form, likely helps direct the suction flow toward the ventral food capturing area. In sum, the tradeoff between swimming speed and predation risks may have been an important factor in the evolution of the observed larval forms.

How zebrafish turn: analysis of pressure force dynamics and mechanical work.

Whereas many fishes swim steadily, zebrafish regularly exhibit unsteady burst-and-coast swimming, which is characterized by repeated sequences of turns followed by gliding periods. Such a behavior offers the opportunity to investigate the hypothesis that negative mechanical work occurs in posterior regions of the body during early phases of the turn near the time of maximal body curvature. Here, we used a modified particle image velocimetry (PIV) technique to obtain high-resolution flow fields around the zebrafish body during turns. Using detailed swimming kinematics coupled with body surface pressure computations, we estimated fluid-structure interaction forces and the pattern of forces and torques along the body during turning. We then calculated the mechanical work done by each body segment. We used estimated patterns of positive and negative work along the body to evaluate the hypothesis (based on fish midline kinematics) that the posterior body region would experience predominantly negative work. Between 10% and 20% of the total mechanical work was done by the fluid on the body (negative work), and negative work was concentrated in the anterior and middle areas of the body, not along the caudal region. Energetic costs of turning were calculated by considering the sum of positive and negative work and were compared with previous metabolic estimates of turning energetics in fishes. The analytical workflow presented here provides a rigorous way to quantify hydrodynamic mechanisms of fish locomotion and facilitates the understanding of how body kinematics generate locomotor forces in freely swimming fishes.

The Use of Wearable Sensors in Human Movement Analysis in Non-Swimming Aquatic Activities: A Systematic Review.

The use of smart technology, specifically inertial sensors (accelerometers, gyroscopes, and magnetometers), to analyze swimming kinematics is being reported in the literature. However, little is known about the usage/application of such sensors in other human aquatic exercises. As the sensors are getting smaller, less expensive, and simple to deal with (regarding data acquisition), one might consider that its application to a broader range of exercises should be a reality. The aim of this systematic review was to update the state of the art about the framework related to the use of sensors assessing human movement in an aquatic environment, besides swimming. The following databases were used: IEEE Xplore, Pubmed, Science Direct, Scopus, and Web of Science. Five articles published in indexed journals, aiming to assess human exercises/movements in the aquatic environment were reviewed. The data from the five articles was categorized and summarized based on the aim, purpose, participants, sensor’s specifications, body area and variables analyzed, and data analysis and statistics. The analyzed studies aimed to compare the movement/exercise kinematics between environments (i.e., dry land versus aquatic), and in some cases compared healthy to pathological participants. The use of sensors in a rehabilitation/hydrotherapy perspective may provide major advantages for therapists.

Effect of swarm configuration on fluid transport during vertical collective motion

Understanding the hydrodynamics of self-propelled organisms is critical to evaluate the role of migrating zooplankton aggregations in sustaining marine ecosystems via the transport of nutrients and mixing of fluid properties. Analysis of transport and mixing during swimming is thus essential to assess whether biomixing is a relevant source of kinetic energy in the upper ocean. In this study, dilute swarms of the ephyral Aurelia aurita were simulated under different configurations to analyze the effects of inter-organism spacing and structure of a migrating aggregation on fluid transport. By using velocimetry data instead of numerically simulated velocity fields, our study integrates the effects of the near- and far-field flows. Lagrangian analysis of simulated fluid particles, both in homogeneous and stratified fluid, shows that the near-field flow ultimately dictates fluid dispersion. The discrepancy between our results and predictions made using low-order models (both in idealized fluid and within the Stokes limit) highlights the need to correctly represent the near-field flow resulting from swimming kinematics and organism morphology. Derived vertical stirring coefficients for all cases suggest that even in the limit of dilute aggregations, self-propelled organisms can play an important role in transporting fluid against density gradients.

Swimming performance is reduced by reflective markers intended for the analysis of swimming kinematics

The present study aimed to clarify whether swimming performance is affected by reflective markers being attached to the swimmer’s body, as is required for a kinematic analysis of swimming. Fourteen well-trained male swimmers (21.1 ± 1.7 yrs) performed maximal 50 m front crawl swimming with (W) and without (WO) 25 reflective markers attached to their skin and swimwear. This number represents the minimum required to estimate the body’s center of mass. Fifty meter swimming time, mid-pool swimming velocity, stroke rate, and stroke length were determined using video analysis. We found swimming time to be 3.9 ± 1.6% longer for W condition. Swimming velocity (3.3 ± 1.8%), stroke rate (1.2 ± 2.0%), and stroke length (2.1 ± 2.7%) were also significantly lower for W condition. To elucidate whether the observed reduction in performance was potentially owing to an additional drag force induced by the reflective markers, measured swimming velocity under W condition was compared to a predicted velocity that was calculated based on swimming velocity obtained under WO condition and an estimate of the additional drag force induced by the reflective markers. The mean prediction error and ICC (2,1) for this analysis of measured and predicted velocities was 0.014 m s−1 and 0.894, respectively. Reducing the drag force term led to a decrease in the degree of agreement between the velocities. Together, these results suggest that the reduction in swimming performance resulted, at least in part, from an additional drag force produced by the reflective markers.

Further characterization of the zebrafish model of acrylamide acute neurotoxicity: gait abnormalities and oxidative stress

Occupational, accidental, or suicidal exposure to acrylamide (ACR) may result in a neurotoxic syndrome. Development of animal models of acrylamide neurotoxicity is necessary for increasing our mechanistic understanding of this syndrome and developing more effective therapies. A new model for acute ACR neurotoxicity has been recently developed in adult zebrafish. Whereas the results of the initial characterization were really promising, a further characterization is needed for testing the construct validity of the model. In this study, the presence of gait abnormalities has been investigated by using ZebraGait, software specifically designed to analyze the kinematics of fish swimming in a water tunnel. The results of the kinematic analyses demonstrated that the model exhibits mild-to-moderate gait abnormalities. Moreover, the model exhibited negative scototaxis, a result confirming a phenotype of anxiety comorbid with depression phenotype. Interestingly, depletion of the reduced glutathione levels was found in the brain without a concomitant increase in oxidative stress. Finally, hypolocomotion and positive geotaxis exhibited by this model were fully recovered 5 days after transferring the fish to clean fish-water. All this data support the validity of the ACR acute neurotoxicity model developed in adult zebrafish.

Swimming kinematics and temperature effects on spermatozoa from wild and captive shortnose sturgeon (Acipenser brevirostrum)

Computer-assisted semen analysis (CASA) and cluster analysis were used to compare spermatozoa swimming kinematics and milt quality between wild and captive shortnose sturgeon (Acipenser brevirostrum). Milt samples from 27 shortnose sturgeon were collected in May 2016 and June 2017. Of these, 19 were wild caught in the Saint John River, New Brunswick, Canada, and eight were from a captive population at the Mactaquac Biodiversity facility. The following kinematic variables were measured immediately following sperm activation (˜5 s), at 30, 60, and 180 s post-activation; average path velocity (VAP); straight-line velocity (VSL); curvilinear velocity (VCL); amplitude of lateral head displacement (ALH); beat cross frequency (BCF); straightness (STR); linearity (LIN); wobble (WOB); percent motility (MOT). Analyses were conducted at 7, 10, and 14 °C to determine potential effects of temperature on kinematics. Principal components analysis (PCA) of original kinematic variables yielded two main components, a speed/wobble component along with a movement pattern component. Hierarchical cluster analysis (HCPC) indicated there were distinct subpopulations, with composition of clusters the result of fish source (wild-caught or captive). Wild-caught fish had greater sperm densities (P = 0.0064) and sperm swimming speeds compared to captive fish (P < 0.05). Temperature had a significant effect only on captive spermatozoa, and this result was not consistent between time periods. There was no effect of hormonal manipulation on spermatozoa motility kinematics. Results indicate there are significant differences in measures of milt quality between wild and captive shortnose sturgeon, indicating an effect of rearing condition on reproductive potential, which may affect fertilization success.

Self-centering characteristics of a petal-shaped capsule robot

Based on the multiple wedge effects, a petal-shaped capsule robot (PCR) is proposed, and the self-centering phenomenon of the PCR is discovered. For investigating the self-centering characteristics, an innovative concept of the instantaneous fluid membrane (FM) thickness, along with the dynamic FM thickness, is proposed; thus a dynamic FM thickness model and a hydrodynamic pressure (HP) model are derived when the PCR axis deviates from the pipe axis under the effect of gravity. A kinematics equation during suspending process in the vertical direction and a swimming kinematics equation in axial direction are derived respectively. Four capsule robots with different eccentricities of the tiles were manufactured and tested, the theoretical and experimental results show that the HP gradient is a fundamental reason for the self-centering phenomenon. The PCR with the self-centering ability can directly avoid the contact with the bottom of the gastrointestinal (GI) tract, achieving the excellent obstacle surmounting ability in the GI complex environment with the less twisted impact on the GI tract, which has a promising application prospect in the GI diagnosis.

Urbanization Alters Swimming Performance of a Stream Fish

Human activities cause many changes in wildlife populations, including phenotypic shifts that represent adaptations to new conditions and influence population dynamics, diversity, and persistence. Although many examples of phenotypic adjustment to anthropogenic disturbance exist, we rarely know the extent to which these changes result from genetic evolution or phenotypic plasticity. Furthermore, our understanding of how whole-organism performance changes as a result of habitat alteration is very limited. We tested how urbanization, an important type of global disturbance, influences fish swimming performance in urban streams. Because urban streams have higher water velocities during rain events than rural streams, we tested for increased steady-swimming performance in fish from urbanized watersheds. Across ten populations of wild-caught Creek Chub (Semotilus atromaculatus), we found that fish from streams in more urbanized areas exhibited a longer propulsive wavelength and a lower tailbeat frequency, expending lower levels of hydromechanical power during steady swimming. In a laboratory experiment, we reared individuals collected as fry from four populations with different urbanization histories, and found evidence for genetically based differences in swimming kinematics. Laboratory-reared fish derived from urbanized populations exhibited higher locomotor efficiency, matching predictions for adaptation to urban environments. We exposed laboratory-reared Creek Chub from urban and rural populations to artificially increased water velocity for four months and observed that only some populations exhibited plasticity. Urban populations may have lost maladaptive, velocity-induced plasticity in locomotor efficiency that is still present in rural populations. Evolutionary change in freshwater species may represent a widespread yet unrecognized consequence of anthropogenic activity.