Size-related effects and the influence of metabolic traits and morphology on swimming performance in fish

Energy metabolism fuels swimming and other biological processes. We compared the swimming performance and energy metabolism within and across eight freshwater fish species. Using swim tunnel respirometers, we measured the standard metabolic rate (SMR) and maximum metabolic rate (MMR) and calculated the critical swimming speed (U_crit). We accounted for body size, metabolic traits, and some morphometric ratios in an effort to understand the extent and underlying causes of variation. Body mass was largely the best predictor of swimming capacity and metabolic traits within species. Moreover, we found that predictive models using total length or SMR, in addition to body mass, significantly increased the explained variation of U_crit and MMR in certain fish species. These predictive models also underlined that, once body mass has been accounted for, U_crit can be independently affected by total length or MMR. This study exemplifies the utility of multiple regression models to assess within-species variability. At interspecific level, our results showed that variation in U_crit can partly be explained by the variation in the interrelated traits of MMR, fineness, and muscle ratios. Among the species studied, bleak Alburnus alburnus performed best in terms of swimming performance and efficiency. By contrast, pumpkinseed Lepomis gibbosus showed very poor swimming performance, but attained lower mass-specific cost of transport (MCOT) than some rheophilic species, possibly reflecting a cost reduction strategy to compensate for hydrodynamic disadvantages. In conclusion, this study provides insight into the key factors influencing the swimming performance of fish at both intra- and interspecific levels.     

Pop up satellite tags impair swimming performance and energetics of the European eel (Anguilla anguilla)

Pop-up satellite archival tags (PSATs) have recently been applied in attempts to follow the oceanic spawning migration of the European eel. PSATs are quite large, and in all likelihood their hydraulic drag constitutes an additional cost during swimming, which remains to be quantified, as does the potential implication for successful migration. Silver eels (L_T = 598.6±29 mm SD, N = 9) were subjected to swimming trials in a Steffensen-type swim tunnel at increasing speeds of 0.3–0.9 body lengths s⁻¹, first without and subsequently with, a scaled down PSAT dummy attached. The tag significantly increased oxygen consumption (MO₂) during swimming and elevated minimum cost of transport (COT_min) by 26%. Standard (SMR) and active metabolic rate (AMR) as well as metabolic scope remained unaffected, suggesting that the observed effects were caused by increased drag. Optimal swimming speed (U _opt) was unchanged, whereas critical swimming speed (U _crit) decreased significantly. Swimming with a PSAT altered swimming kinematics as verified by significant changes to tail beat frequency (f), body wave speed (v) and Strouhal number (St). The results demonstrate that energy expenditure, swimming performance and efficiency all are significantly affected in migrating eels with external tags.     

The Effect of Drag and Attachment Site of External Tags on Swimming Eels: Experimental Quantification and Evaluation Tool

Telemetry studies on aquatic animals often use external tags to monitor migration patterns and help to inform conservation effort. However, external tags are known to impair swimming energetics dramatically in a variety of species, including the endangered European eel. Due to their high swimming efficiency, anguilliform swimmers are very susceptibility for added drag. Using an integration of swimming physiology, behaviour and kinematics, we investigated the effect of additional drag and site of externally attached tags on swimming mode and costs. The results show a significant effect of a) attachment site and b) drag on multiple energetic parameters, such as Cost Of Transport (COT), critical swimming speed (U_crit) and optimal swimming speed (U_opt), possibly due to changes in swimming kinematics. Attachment at 0.125 bl from the tip of the snout is a better choice than at the Centre Of Mass (0.35 bl), as it is the case in current telemetry studies. Quantification of added drag effect on COT and U_crit show a (limited) correlation, suggesting that the U_crit test can be used for evaluating external tags for telemetry studies until a certain threshold value. U_opt is not affected by added drag, validating previous findings of telemetry studies. The integrative methodology and the evaluation tool presented here can be used for the design of new studies using external telemetry tags, and the (re-) evaluation of relevant studies on anguilliform swimmers.     

Disentangling the functional roles of morphology and motion in the swimming of fish

In fishes the shape of the body and the swimming mode generally are correlated. Slender-bodied fishes such as eels, lampreys, and many sharks tend to swim in the anguilliform mode, in which much of the body undulates at high amplitude. Fishes with broad tails and a narrow caudal peduncle, in contrast, tend to swim in the carangiform mode, in which the tail undulates at high amplitude. Such fishes also tend to have different wake structures. Carangiform swimmers generally produce two staggered vortices per tail beat and a strong downstream jet, while anguilliform swimmers produce a more complex wake, containing at least two pairs of vortices per tail beat and relatively little downstream flow. Are these differences a result of the different swimming modes or of the different body shapes, or both? Disentangling the functional roles requires a multipronged approach, using experiments on live fishes as well as computational simulations and physical models. We present experimental results from swimming eels (anguilliform), bluegill sunfish (carangiform), and rainbow trout (subcarangiform) that demonstrate differences in the wakes and in swimming performance. The swimming of mackerel and lamprey was also simulated computationally with realistic body shapes and both swimming modes: the normal carangiform mackerel and anguilliform lamprey, then an anguilliform mackerel and carangiform lamprey. The gross structure of simulated wakes (single versus double vortex row) depended strongly on Strouhal number, while body shape influenced the complexity of the vortex row, and the swimming mode had the weakest effect. Performance was affected even by small differences in the wakes: both experimental and computational results indicate that anguilliform swimmers are more efficient at lower swimming speeds, while carangiform swimmers are more efficient at high speed. At high Reynolds number, the lamprey-shaped swimmer produced a more complex wake than the mackerel-shaped swimmer, similar to the experimental results. Finally, we show results from a simple physical model of a flapping fin, using fins of different flexural stiffness. When actuated in the same way, fins of different stiffnesses propel themselves at different speeds with different kinematics. Future experimental and computational work will need to consider the mechanisms underlying production of the anguilliform and carangiform swimming modes, because anguilliform swimmers tend to be less stiff, in general, than are carangiform swimmers.     

Swimming efficiency and the influence of morphology on swimming costs in fishes

Swimming performance is considered a main character determining survival in many aquatic animals. Body morphology highly influences the energetic costs and efficiency of swimming and sets general limits on a species capacity to use habitats and foods. For two cyprinid fishes with different morphological characteristics, carp (Cyprinus carpio L.) and roach (Rutilus rutilus (L.)), optimum swimming speeds (U _mc) as well as total and net costs of transport (COT, NCOT) were determined to evaluate differences in their swimming efficiency. Costs of transport and optimum speeds proved to be allometric functions of fish mass. NCOT was higher but U _mc was lower in carp, indicating a lower swimming efficiency compared to roach. The differences in swimming costs are attributed to the different ecological demands of the species and could partly be explained by their morphological characteristics. Body fineness ratios were used to quantify the influence of body shape on activity costs. This factor proved to be significantly different between the species, indicating a better streamlining in roach with values closer to the optimum body form for efficient swimming. Net swimming costs were directly related to fish morphology.     

An interspecific comparison between morphology and swimming performance in cyprinids

Flow regimes are believed to be of major evolutionary significance in fish. The flow regimes inhabited by cyprinids vary extensively from still flow regimes to riptide flow regimes. To test (i) whether flow‐driven swimming performance and relevant morphological differentiation are present among fish species and (ii) whether evolutionary shifts between high‐flow and low‐flow habitats in cyprinids are associated with evolutionary trade‐offs in locomotor performance, we obtained data on both steady and unsteady swimming performance and external body shape for 19 species of cyprinids that typically occur in different flow regimes (still, intermediate and riptide). We also measured the routine energy expenditure (RMR) and maximum metabolic rate (MMR) and calculated the optimal swimming speed. Our results showed that fish species from riptide groups tend to have a higher critical swimming speed (U_crit), maximum linear velocity (V_max) and fineness ratio (FR) than fish from the other two groups. However, there was no correlation between the reconstructed changes in the steady and unsteady swimming performance of the 19 species. According to the phylogenetically independent contrast (PIC) method, the U_crit was actively correlated with the MMR. These results indicated that selection will favour both higher steady and unsteady swimming performance and a more streamlined body shape in environments with high water velocities. The results suggested that steady swimming performance was more sensitive to the flow regime and that for this reason, changes in body shape resulted more from selective pressure on steady swimming performance than on unsteady swimming performance. No evolutionary trade‐off was observed between steady and unsteady swimming performance, although U_crit and MMR were found to have coevolved. However, a further analysis within each typically occurring habitat group suggested that the trade‐off that may exist between steady and unsteady swimming performance may be concealed by the effect of habitat.     

Reduction in swimming performance in juvenile rainbow trout (Oncorhynchus mykiss) following sublethal exposure to pyrethroid insecticides

While the lethal toxicity of pyrethroid insecticides to fish is well documented, their sublethal physio-behavioral effects remain poorly characterized. Known pyrethroid-associated changes to insect neuromuscular function may translate into similar effects in fish, thereby altering swimming ability and affecting foraging, predator avoidance, and migration. Three experiments were conducted using critical (U_crit) and burst (U_max) swimming speeds to assess the sublethal effects of the pyrethroids permethrin and deltamethrin in juvenile rainbow trout (Oncorhynchus mykiss). Fish were exposed to deltamethrin (100, 200, or 300 ng/L) or permethrin (1, 2, or 3 μg/L) in water for 4 d, and assessed for swimming performance. Deltamethrin (200 and 300 ng/L) reduced U_crit, but not U_max, while both swim performance measurements were unaffected by permethrin. Subsequent experiments used only U_crit to assess deltamethrin exposure. In a time course experiment, deltamethrin (300 ng/L) reduced U_crit after 1 and 4 d of exposure, but after 7 d of exposure U_crit was fully recovered. Finally, deltamethrin (1, 2, or 3 μg/L) reduced U_crit after 1 h bath exposures similar to recommended protocols for deltamethrin based sea-lice treatment in aquaculture. The real-world implications of the revealed pyrethroid-associated swimming ability reductions in salmon may be important in areas close to aquaculture facilities.     

Helical swimming can provide robust upwards transport for gravitactic single-cell algae; a mechanistic model

In still fluid, many phytoplankton swim in helical paths with an average upwards motion. A new mechanistic model for gravitactic algae subject to an intrinsic torque is developed here, based on Heterosigma akashiwo, which results in upwards helical trajectories in still fluid. The resultant upwards swimming speed is calculated as a function of the gravitactic and intrinsic torques. Helical swimmers have a reduced upwards speed in still fluid compared to cells which swim straight upwards. However a novel result is obtained when the effect of fluid shear is considered. For intermediate values of shear and intrinsic torque, a new stable equilibrium solution for swimming direction is obtained for helical swimmers. This results in positive upwards transport in vertical shear flow, in contrast to the stable equilibrium solution for straight swimmers which results in downwards transport in vertical shear flow. Furthermore, for strong intrinsic torque, when there is no longer a stable orientation equilibrium, we show that the average downwards transport of helical swimmers in vertical shear flow is greatly suppressed compared to straight swimmers. We hypothesise that helical swimming provides robustness for upwards transport in the presence of fluid shearing motions.     

Ontogenetic changes in the critical swimming speed of Gadus morhua (Atlantic cod) and Myoxocephalus scorpius (shorthorn sculpin) larvae and the role of temperature

Most studies on behavioural contributions to dispersal and recruitment during early life history stages of fishes have focused on coral reef species. For cold ocean environments, high variation in seasonal temperature and development times suggest that parallel studies on active behaviour are needed for cold-water species. Thus, we examined the critical swimming speed (U_crit) of marine fish larvae from 2 contrasting species: Gadus morhua (Atlantic cod) and Myoxocephalus scorpius (shorthorn sculpin), a pelagic and bottom spawner respectively. Within-species comparisons showed that sculpin reared at 6 °C had lower initial U_crit values, but a faster U_crit increase through development compared with 3 °C conspecifics, ultimately resulting in faster critical swimming speeds at metamorphosis (10.5 vs. 9.1 cm·s^− 1). In contrast, although cod larvae reared at 10 °C were faster swimmers at first feeding than 6 °C fish, temperature differences were absent after the first week. These results show that temperature influences the trajectory of larval critical swimming speed development, but that the relationship is species-specific. Although 6 °C sculpin and cod of similar length had equivalent U_crit values, the smaller size of cod at hatch (5.3 vs. 10.8 mm for sculpin) resulted in much lower age-specific U_crit values for cod. These data have significant implications for how swimming activity of the two species might affect dispersal, particularly in the first few weeks post-hatch. Overall, our data suggest that temperature during larval development influences the swimming capacity of cold-water marine fishes, and has important ramifications for biophysical models of dispersal.     

Integrating environmental variation, predation pressure, phenotypic plasticity and locomotor performance

The Wujiang River, a tributary of the Three Gorges Reservoir, has many dams along its length. These dams alter the river's natural habitat and produce various flow regimes and degrees of predator stress. To test whether the swimming performance and external body shape of pale chub (Zacco platypus) have changed as a result of alterations in the flow regime and predator conditions, we measured the steady (U _crit) and unsteady (fast-start) swimming performances and morphological characteristics of fish collected from different sites along the Wujiang River. We also calculated the maximum respiratory capacity and cost of transport (COT). We demonstrated significant differences in swimming performance and morphological traits among the sampling sites. Steady swimming performance was positively correlated with water velocity and negatively correlated with the abundance of predators, whereas unsteady swimming performance was negatively correlated with water velocity. The body shape was significantly correlated with both swimming performance and ecological parameters. These findings suggested that selection pressure on swimming performance results in a higher U _crit and a more streamlined body shape in fast-flow and (or) in habitats with low predator stress and subsequently results in a lower COT. These characteristics were accompanied by a poorer fast-start performance than that of the fish from the slow-flow and (or) high-predator habitats. The divergence in U _crit may also be due in part to variation in respiratory capacity.     

Fish functional design and swimming performance

Classifications of fish swimming are reviewed as a prelude to discussing functional design and performance in an ecological context. Webb (1984a , 1998 ) classified fishes based on body shape and locomotor mode into three basic categories: body and caudal fin (BCF) periodic, BCF transient (fast‐starts, turns) and median and paired fin (MPF) swimmers. Swimming performance and functional design is discussed for each of these categories. Webb hypothesized that specialization in any given category would limit performance in any other. For example, routine MPF swimmers should be penalized in BCF transient (fast‐start propulsion). Recent studies offer much support for Webb's construct but also suggest some necessary amendments. In particular, design and performance compromises for different swimming modes are associated with fish that employ the same propulsor for more than one task (coupled, e.g. the same propulsor for routine steady swimming and fast‐starts). For example, pike (BCF transient specialist) achieve better acceleration performance than trout (generalist). Pike steady (BCF periodic) performance, however, is inferior to that of trout. Fish that employ different propulsors for different tasks (decoupled, e.g. MPF propulsion for low‐speed routine swimming and BCF motions for fast‐starts) do not show serious performance compromises. For example, certain MPF low‐speed swimmers show comparable fast‐start performance to BCF forms. Arguably, the evolution of decoupled locomotor systems was a major factor underlying the adaptive radiation of teleosts. Low‐speed routine propulsion releases MPF swimmers from the morphological constraints imposed by streamlining allowing for a high degree of variability in form. This contrasts with BCF periodic swimming specialists where representatives of four vertebrate classes show evolutionary convergence on a single, optimal ‘thunniform’ design. However, recent experimental studies on the comparative performance of carangiform and thunniform swimmers contradict some of the predictions of hydromechanical models. This is addressed in regard to the swimming performance, energetics and muscle physiology of tuna. The concept of gait is reviewed in the context of coupled and decoupled locomotor systems. Biomimetic approaches to the development of Autonomous Underwater Vehicles have given a new context and impetus to research and this is discussed in relation to current views of fish functional design and swimming performance. Suggestions are made for possible future research directions.     

Reynolds number limits for jet propulsion: a numerical study of simplified jellyfish

The Scallop theorem states that reciprocal methods of locomotion, such as jet propulsion or paddling, will not work in Stokes flow (Reynolds number=0). In nature the effective limit of jet propulsion is still in the range where inertial forces are significant. It appears that almost all animals that use jet propulsion swim at Reynolds numbers (Re) of about 5 or more. Juvenile squid and octopods hatch from the egg already swimming in this inertial regime. Juvenile jellyfish, or ephyrae, break off from polyps swimming at Re greater than 5. Many other organisms, such as scallops, rarely swim at Re less than 100. The limitations of jet propulsion at intermediate Re is explored here using the immersed boundary method to solve the 2D Navier-Stokes equations coupled to the motion of a simplified jellyfish. The contraction and expansion kinematics are prescribed, but the forward and backward swimming motions of the idealized jellyfish are emergent properties determined by the resulting fluid dynamics. Simulations are performed for both an oblate bell shape using a paddling mode of swimming and a prolate bell shape using jet propulsion. Average forward velocities and work put into the system are calculated for Re between 1 and 320. The results show that forward velocities rapidly decay with decreasing Re for all bell shapes when Re<10. Similarly, the work required to generate the pulsing motion increases significantly for Re<10. When compared to actual organisms, the swimming velocities and vortex separation patterns for the model prolate agree with those observed in Nemopsis bachei. The forward swimming velocities of the model oblate jellyfish after two pulse cycles are comparable to those reported for Aurelia aurita, but discrepancies are observed in the vortex dynamics between when the 2D model oblate jellyfish and the organism. This discrepancy is likely due to a combination of the differences between the 3D reality of the jellyfish and the 2D simplification, as well as the rigidity of the time varying geometry imposed by the idealized model.     

The role of mechanical resonance in the neural control of swimming in fishes

The bodies of many fishes are flexible, elastic structures; if you bend them, they spring back. Therefore, they should have a resonant frequency: a bending frequency at which the output amplitude is maximized for a particular input. Previous groups have hypothesized that swimming at this resonant frequency could maximize efficiency, and that a neural circuit called the central pattern generator might be able to entrain to a mechanical resonance. However, fishes swim in water, which may potentially damp out many resonant effects. Additionally, their bodies are elongated, which means that bending can occur in complicated ways along the length of the body. We review previous studies of the mechanical properties of fish bodies, and then present new data that demonstrate complex bending properties of elongated fish bodies. Resonant peaks in amplitude exist, but there may be many of them depending on the body wavelength. Additionally, they may not correspond to the maximum swimming speed. Next, we describe experiments using a closed-loop preparation of the lamprey, in which a preparation of the spinal cord is linked to a real-time simulation of the muscle and body properties, allowing us to examine resonance entrainment as we vary the simulated resonant frequency. We find that resonance entrainment does occur, but is rare. Gain had a significant, though weak, effect, and a nonlinear muscle model produced resonance entrainment more often than a linear filter. We speculate that resonance may not be a critical effect for efficient swimming in elongate, anguilliform swimmers, though it may be more important for stiffer carangiform and thunniform fishes.     

Discovery of swimming larvae in Elmidae (Coleoptera: Byrrhoidea)

The aquatic larvae of the family Elmidae (Coleoptera) have been considered unable to swim because they lack swimming setae on their body and legs. We discovered that riffle beetle larvae (Leptelmis gracilis Sharp) are in fact able to swim. After opening the tuft‐like gills on the last abdominal segment they swim by repeatedly bending the abdomen into a U‐shape very quickly and in a wavy manner, while their head and thorax move anteriorly, resulting in a sigmoidal body shape. The flat bodies of L. gracilis larvae could be advantageous for swimming compared to the cylindrical or semicylindrical bodies of larvae in related genera.     

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

This study compared the critical swimming speed (U_crit) and endurance performance of three Australian freshwater fish species in different swim‐test apparatus. Estimates of U_crit 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.     

Effect of body roll amplitude and arm rotation speed on propulsion of arm amputee swimmers

Only a limited amount of research has gone into evaluating the contribution made by the upper arm to the propulsion of elite swimmers with an amputation at elbow level. With assistance of computational fluid dynamics (CFD) modelling, the swimming technique of competitive arm amputee swimmers can be assessed through numerical simulations which test the effect of various parameters on the effectiveness of the swimming propulsion.This numerical study investigates the effect of body roll amplitude and of upper arm rotation speed on the propulsion of an arm amputee swimmer, at different mean swimming speeds. Various test cases are simulated resulting in a thorough analysis of the complex body/fluid interaction with a detailed quantitative assessment of the effect of the variation of each parameter on the arm propulsion. It is found that a body roll movement with an amplitude of 45° enhances greatly the propulsive contribution from the upper arm with an increase of about 70% in the propulsive force compared to the no roll condition. An increase in the angular velocity of the upper arm also leads to a concomitant increase in the propulsive forces produced by the arm.Such results have direct implications for competitive arm amputee front crawl swimmers and for those who coach them. One important message that emerges in this present work is that there exists, for any given swimming speed, a minimum angular velocity at which the upper arm must be rotated to generate effective propulsion. Below this velocity, the upper arm will experience a net resistive drag force which adversely affects swimming performance.     

Establishing zebrafish as a novel exercise model: swimming economy, swimming-enhanced growth and muscle growth marker gene expression

Background

Zebrafish has been largely accepted as a vertebrate multidisciplinary model but its usefulness as a model for exercise physiology has been hampered by the scarce knowledge on its swimming economy, optimal swimming speeds and cost of transport. Therefore, we have performed individual and group-wise swimming experiments to quantify swimming economy and to demonstrate the exercise effects on growth in adult zebrafish.

Methodology/Principal Findings

Individual zebrafish (n = 10) were able to swim at a critical swimming speed (U_crit) of 0.548±0.007 m s⁻¹ or 18.0 standard body lengths (BL) s⁻¹. The optimal swimming speed (U_opt) at which energetic efficiency is highest was 0.396±0.019 m s⁻¹ (13.0 BL s⁻¹) corresponding to 72.26±0.29% of U_crit. The cost of transport at optimal swimming speed (COT_opt) was 25.23±4.03 µmol g⁻¹ m⁻¹. A group-wise experiment was conducted with zebrafish (n = 83) swimming at U_opt for 6 h day⁻¹ for 5 days week⁻¹ for 4 weeks vs. zebrafish (n = 84) that rested during this period. Swimming zebrafish increased their total body length by 5.6% and body weight by 41.1% as compared to resting fish. For the first time, a highly significant exercise-induced growth is demonstrated in adult zebrafish. Expression analysis of a set of muscle growth marker genes revealed clear regulatory roles in relation to swimming-enhanced growth for genes such as growth hormone receptor b (ghrb), insulin-like growth factor 1 receptor a (igf1ra), troponin C (stnnc), slow myosin heavy chain 1 (smyhc1), troponin I2 (tnni2), myosin heavy polypeptide 2 (myhz2) and myostatin (mstnb).

Conclusions/Significance

From the results of our study we can conclude that zebrafish can be used as an exercise model for enhanced growth, with implications in basic, biomedical and applied sciences, such as aquaculture.     

Laboratory protocol to calibrate sea lamprey (<Emphasis Type="Italic">Petromyzon marinus</Emphasis> L.) EMG signal output with swimming

A correct application of electromyogram (EMG) telemetry in the field can be a powerful tool to evaluate activity patterns and swimming strategies of fishes. We evaluated the swim performance of seven untagged sea lampreys (Petromyzon marinus L.) with critical swim speed (U _crit) tests. The average U _crit observed was c. 1.03 ms⁻¹ (i.e., 1.14 BL s⁻¹). The strongest reotaxic response was observed during tests using water velocities between 0.4 ms⁻¹ and 0.8 ms⁻¹. During two consecutive years (i.e., 2004 and 2005), in order to model upstream migration of sea lampreys with CEMG transmitters (Lotek Wireless), we calibrated EMG signal with swim speed. A high correlation between EMG records and swim speed was observed in both years (r ² = 0.74–0.93). However, in spite of methodology improvements and standardization in the second year of study, differences in intercepts and slopes were observed between individuals, making the determination of a unique calibration equation for all tagged animals unfeasible. Therefore, it appears to be necessary to obtain the relationship between EMG signals and swimming speed for each lamprey using laboratory procedures, prior to release in the wild. It is unknown whether this variability results from individual locomotor behaviour, physiological state and/or variation in placement and functioning of the EMG transmitters. The results of five laboratory calibrated lampreys, released in the River Mondego, revealed considerable differences between swim speeds calculated with EMG signal (calibration equation) and ground speed therefore it was not possible to successfully calibrate the EMG signal output with swimming speed. In order to accomplish this, longer continuous swimming tests in laboratory are necessary. Nevertheless, the calibrated swimming effort gives reliable information about the swimming behaviour and permits comparison of the results between animals.     

Locomotion at –1.0°C: burst swimming performance of five species of Antarctic fish

We investigated the burst swimming performance of five species of Antarctic fish at −1.0°C. The species studied belonged to the suborder, Notothenioidei, and from the families, Nototheniidae and Bathydraconidae. Swimming performance of the fish was assessed over the initial 300 ms of a startle response using surgically attached miniature accelerometers. Escape responses in all fish consisted of a C-type fast start; consisting of an initial pronounced bending of the body into a C-shape, followed by one or more complete tail-beats and an un-powered glide. We found significant differences in the swimming performance of the five species of fish examined, with average maximum swimming velocities (U_max) ranging from 0.91 to 1.39 m s⁻¹ and maximum accelerations (A_max) ranging from 10.6 to 15.6 m s⁻². The cryopelagic species, Pagothenia borchgrevinki, produced the fastest escape response, reaching a U_max and A_max of 1.39 m s⁻¹ and 15.6 m s⁻², respectively. We also compared the body shapes of each fish species with their measures of maximum burst performance. The dragonfish, Gymnodraco acuticeps, from the family Bathdraconidae, did not conform to the pattern observed for the other four fish species belonging to the family Nototheniidae. However, we found a negative relationship between buoyancy of the fish species and burst swimming performance.