Swimming Capacity Research Articles

Inferring fish behaviour at the trawl mouth from escape location.

In this study, we used escape location underneath the trawl to understand groundfish herding behaviour at the trawl mouth. Three collecting bags (port, center, starboard) were mounted under the trawl and behind the footgear to collect escapees. The escape-at-length of species that escaped into the center bag were compared to the two wing bags to infer fish response behaviour, herding behaviour, and swimming capacity at the trawl mouth. For roundfish, smaller-sized individuals escaped more in the center for both Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus), <20 and 11 cm, respectively, indicating that larger-sized fish were to a greater extent seeking to escape under the trawl at the wings, vs small fish being herded to the center and likely overrun due to reduced swimming capacity. For flatfish and monkfish (Lophius piscatorius), results varied. European plaice (Pleuronectes platessa), American plaice (Hippoglossoides platessoides), and monkfish were caught most often in the wings, though not significantly for American plaice. Catches of dab (Limanda limanda) between 18 and 27 cm were significantly higher in the center, with no difference for smaller and larger individuals. The differences between fish escape location likely result from a combination of varying herding behaviour, size, and swimming capacity. Here, we were able to show how these size-dependent behaviours relate to fish response behaviour, escape behaviour, size, and likely swimming capacity.

Seasonal temperatures in South Eleuthera, The Bahamas, have considerable impacts on the cardiorespiratory function and swimming performance of Nassau grouper (Epinephelus striatus)

Abstract Surprisingly, the impacts of environmental changes on the physiology of tropical/subtropical marine fishes have received limited attention. Given that (i) temperature is considered to be a key factor controlling the biology of fishes; (ii) no published data are available on the swimming performance, metabolic capacity or cardiac function of any of the ~165 grouper species worldwide; and (iii) the Nassau grouper is an endangered species of great ecological and socioeconomic significance in The Bahamas, we investigated how current summer/early fall (30°C) and winter (22°C) temperatures in South Eleuthera affected the aerobic metabolism and heart function of wild Nassau grouper when swum to exhaustion (i.e. to their critical swimming speed, Ucrit). The Nassau grouper had a very low Ucrit at 30°C (i.e. &amp;lt;1 body lengths s−1), and a 30% lower swimming performance during the winter (at 22°C), and this was that was indicative of a reduced absolute aerobic scope (~185 vs. 290 mg O2 kg−1 h−1) and values of maximum heart rate ($f$HMax) and scope for $f$H that were only one-half of that achieved at 30°C (~60 vs. 120 and 29 vs. 61 beats min−1, respectively). Overall, these data reveal that the Nassau grouper’s aerobic and swimming capacity are well below values reported for other tropical/subtropical fishes and suggest that, despite a compensatory (~30–40%) increase in stroke volume, constraints on $f$H near this species’ lower thermal limit negatively affect its cardiac output and swimming performance. These findings have considerable ecological implications as Bahamian grouper populations migrate over long distances to spawn during the winter months, and given the predicted increase in temperature variability with climate change.

Feeding by larval fish: how taxonomy, body length, mouth size, and behaviour contribute to differences among individuals and species from a coastal ecosystem

AbstractData on individual stomach contents were used to describe length-dependent differences in feeding success of larvae of 11 species of fish found in coastal Newfoundland, Canada. Copepods dominated the diet with a gradual shift from nauplii to copepodites in all species. Differences in feeding success in both prey number and gut fullness among individual larvae was linked to increasing individual diet diversity in all taxa, although there was a weak decline in mean prey size. Maxilla and body length, within and among taxa, have a dominant positive influence on the potential feeding success of larval fish. In addition to differences in average stomach weight, the variability in number of prey per stomach among individuals indicates that each species perceives their prey environment in different ways. Taxonomic proximity had limited effect on differences in feeding success among taxa. The results suggest that behavioural differences among individuals and taxa, that likely reflect swimming capacity and/or prey perception/capture ability, are likely to be important elements contributing to feeding success. Body and mouth size may represent key characteristics that should be considered in evaluating differences in feeding success among species as well as among individuals within and among cohorts.

Elevated Embryonic Temperature Has Persistent Adverse Effects on Zebrafish Swimming Capacity

In recent years, global warming of anthropogenic origin and its impacts on biodiversity have increasingly gained public awareness. Here, we demonstrate that embryonic temperature can have persistent and crucial effects on zebrafish swimming capacity and cardiac shape. Three different embryonic temperature treatments (TE = 24, 28 or 32 °C) were applied to zebrafish embryos until hatching. Fish were then raised in common conditions (28 °C) until adulthood. Ventricle roundness was found to increase significantly with a rise in TE in juvenile (10% increase) and male (8% increase), but not female fish. TE and sex significantly affected zebrafish swimming performance. Juveniles, males and females raised in cold (24 °C) presented significantly greater swimming capacity than those raised at 28 and 32 °C TE. Our results represent a direct link between the physical capacity of adult fish and embryonic temperature fluctuations that add to the emerging rationale of the potential climate change scenarios on wild fish populations.

Respiratory substrate preferences in mitochondria isolated from different tissues of three fish species.

Energy requirements of tissues vary greatly and exhibit different mitochondrial respiratory activities with variable participation of both substrates and oxidative phosphorylation. The present study aimed to (1) compare the substrate preferences of mitochondria from different tissues and fish species with different ecological characteristics, (2) identify an appropriate substrate for comparing metabolism by mitochondria from different tissues and species, and (3) explore the relationship between mitochondrial metabolism mechanisms and ecological energetic strategies. Respiration rates and cytochrome c oxidase (CCO) activities of mitochondria isolated from heart, brain, kidney, and other tissues from Silurus meridionalis, Carassius auratus, and Megalobrama amblycephala were measured using succinate (complex II-linked substrate), pyruvate (complex I-linked), glutamate (complex I-linked), or combinations. Mitochondria from all tissues and species exhibited substrate preferences. Mitochondria exhibited greater coupling efficiencies and lower leakage rates using either complex I-linked substrates, whereas an opposite trend was observed for succinate (complex II-linked). Furthermore, maximum mitochondrial respiration rates were higher with the substrate combinations than with individual substrates; therefore, state III respiration rates measured with substrate combinations could be effective indicators of maximum mitochondrial metabolic capacity. Regardless of fish species, both state III respiration rates and CCO activities were the highest in heart mitochondria, followed by red muscle mitochondria. However, differences in substrate preferences were not associated with species feeding habit. The maximum respiration rates of heart mitochondria with substrate combinations could indicate differences in locomotor performances, with higher metabolic rates being associated with greater capacity for sustained swimming.

Sublethal exposure to Microcystis aeruginosa extracts during the yolk-sac larval stage reduces aerobic swimming speed in juvenile zebrafish

This study examined whether the aerobic swimming capacity of zebrafish juveniles is affected by the exposure of the yolk-sac larvae to sublethal concentration of Microcystis aeruginosa extract (200 mg dw L−1). Critical swimming speed significantly decreased in the pre-exposed fish (9.2 ± 1.0 vs 11.3 ± 1.4 TL s−1 in the control group). Exposure did not have any significant effects on the shape of the heart ventricle, rate of skeletal abnormalities, and growth or survival rates. Decreased swimming performance due to the early and short exposure to M. aeruginosa could have negative impacts on fish in the wild.

Allometric Scaling of Anaerobic Capacity Estimated from a Unique Field-Based Data Set of Fish Swimming.

AbstractLocomotion is a defining characteristic that can dictate many aspects of an organism's life history in the pursuit of maximizing fitness, including escaping predators, capturing prey, and transitioning between habitats. Exhaustive exercise can have negative consequences for both short-term and long-term energetics and life history trade-offs, influencing fish survival and reproduction. Studies of swimming performance and exhaustive exercise in fish are often conducted on individual species, but few multispecies analyses exist and even fewer in field settings. In fish, swimming performance and exercise have historically been studied in the laboratory using swim tunnels, but an increasing body of work in recreational fisheries science provides a novel way to examine swimming capacity and exhaustion. Using fight time, the time it takes for a hooked fish to be landed on rod and reel fishing gear, as an opportunistic proxy for fish exhaustion, a multispecies meta-analysis of data from studies on recreational fisheries was conducted to elucidate the factors that most influence capacity for exhaustive exercise. Data from 39 species of freshwater and marine fish were aggregated, and negative binomial mixed effects models as well as phylogenetic least squares regression were used to identify the factors that most influenced exhaustive exercise in the field. Fish total length, aspect ratio of the caudal fin, and body form were significant factors in explaining the capacity for exhaustive exercise. Large migratory fish with high aspect ratios were able to fight, and therefore exercise, the longest. These results illustrate that body form and physiology are both deeply intertwined to inform function across fish species and point to angling fight time as a useful approximation of fish swimming capabilities that can be further developed for understanding the limits of fish exercise physiology.

Impacts of environmental conditions and management of sluice gates on glass eel migration

Anthropogenic barriers such as tidal gates impair animal migration and ecological continuity. For migratory fishes, barriers may alter or impeach both upstream and downstream migrations. Juveniles of European eels, namely glass eels, have to pass those barriers when migrating upstream, whereas they have limited swimming capacities and are dependent on several environmental variables. Hydrological conditions, which can be modified by barrier management, are critical for glass eels. Here, we investigated the links between hydrological conditions and barrier management and the recruitment of glass eels at a connection between the Mediterranean Sea and a lagoon. To do that, we modeled the recruitment of glass eels over ten seasons accounting for temporal variations and co-variable effects. We modeled three aspects of recruitment: presence, level, and composition. We found that monthly and inter-annual effects explained the main part of the variations in glass eel recruitment but accounting for environmental effects improved our models, with a positive effect of temperature, for instance. We associated low levels of catches and recruitment of rather old individuals to high water flow rates when water flows out of the lagoon. Those results call for further studies on how sluice gate management may improve glass eel recruitment and seem to indicate that local stakeholders should adjust the number of open gates depending on the water level on both sides of the barrier.

Medical Swimming Cellbots

To address the issue that synthetic swimming nanorobots are susceptible to immune clearance and fouling in vivo, swimming hybrid cell‐based robots (cellbots) composed of living cells have been developed. Swimming cellbots use living cells such as sperm, bacteria, and algae as fabrication units to obtain the swimming capacity, which can be functionalized by adding different kinds of functional components and cargoes. Swimming cellbots not only inherit the biological functions of natural cells, but also can realize diverse locomotion modes under the action of their synthetic parts. This perspective highlights the fabrication, functionalization and multimode motion control of swimming cellbots, and possible medical application. As a representative example of swimming cellbots, dual‐responsive neutrobots have two driving modes: rotating magnetic field actuation and chemotactic locomotion, which can be utilized to cross the blood–brain barrier and target the glioblastoma in mice. The delivery efficiency of these drug‐loaded neutrobots can reach about 10% which is significantly higher than that of traditional nanocarriers. Such swimming cellbots may load different types of drugs and can be navigated through the combination of natural chemotaxis and externally physical fields such as magnetic, optical, and ultrasonic fields which may have potential in biomedical fields.

Bdnf loss affects activity, sociability, and anxiety-like behaviour in zebrafish

Brain-derived neurotropic factor (BDNF) has established roles in neuronal survival and differentiation, in synaptic plasticity, and in neurotransmitters release. Several lines of evidence suggest that variations in BDNF might alter behaviour and contribute to neurobehavioural disorders. We investigated the functional effects of BDNF loss on behaviour by phenotyping a recently-generated CRISPR/Cas9 bdnf-/- zebrafish line through a battery of behavioural assays. Results of two behavioural tests suggested higher levels of locomotor activity in bdnf-/- zebrafish compared to bdnf+/+ zebrafish, in spite of similar swimming capacities observed in the two lines in a swim tunnel. bdnf-/- zebrafish also displayed higher levels of attraction towards a social stimulus compared to wild-type zebrafish, suggesting an effect of BDNF on sociability. Last, in a scototaxis test, we found evidence of potential differences in anxiety-like behaviour between the two lines. Our study supports an effect of BDNF on several behavioural traits, in line with early studies in mutant rodent models and in humans, suggesting the possibility to use the zebrafish to investigate diseases that involve alteration in BDNF levels.

Transgenerational effects of parental crude oil exposure on the morphology of adult Fundulus grandis.

The current study involved exposing adult F0 Gulf killifish (Fundulus grandis) to Macondo-252 oil for 36 to 44 days and assessing the effects of this oiling on the swimming performance and morphology in two generations of progeny reared in clean water. Following exposure to oil, the F0 fish were used as broodstock to generate four lineages of F1 fish using a full-matrix mating design derived from the gametes of clean and oil-exposed parents. Later, the four lineages of F1 fish were used as broodstock to create an F2 generation of the same four lineages. We found few differences in embryonic outcome (% dead,% hatched, and% unhatched) in any of the four lineages of F1 and F2 fish. However, as adults, F1 and F2 fish derived from oil-exposed males from the F0 generation had significantly lower critical swimming speeds (Ucrit) than both the control and maternally oil-exposed lineages. Additionally, progeny of oil-exposed fish had altered body shape based on the statistical analysis of two-dimensional landmark-based geometric morphometrics. Fish from oil-exposed lineages showed increased body depth, altered spinal curvature, and changes in the upward angle of projection of the head. Both generations had a significant main effect of maternal and paternal oil exposure on shape; however, F0 paternal oil exposure explained more of the variance in shape across both generations relative to F0 maternal exposure. Our findings demonstrate that parental exposure to oil can impact the shape and aerobic swimming capacity of offspring for at least two generations after the original paternal oiling.

Conjugation-mediated transfer of pXO16, a large plasmid from Bacillus thuringiensis sv. israelensis, across the Bacillus cereus group and its impact on host phenotype

pXO16, the 350 kb-conjugative plasmid from Bacillus thuringiensis sv. israelensis promotes its own transfer at high efficiency, triggers the transfer of mobilizable and non-mobilizable plasmids, as well as the transfer of host chromosomal loci. Naturally found in B. thuringiensis sv. israelensis, pXO16 transfers to various strains of Bacillus cereus sensu lato (s.l.) at a wide range of frequencies. Despite this host diversity, a paradox remains between the relatively large host spectrum and the natural occurrence of pXO16, so far restricted to B. thuringiensis sv. israelensis. Proposing first insights exploring this paradox, we investigated the behaviour of pXO16 amongst different members of the B. cereus group. We first looked at the transfer of pXO16 to two new host clusters of B. cereus s.l., Bacillus mycoides and Bacillus anthracis clusters. This examination brought to light the impairment of the characteristic rhizoidal phenotype of B. mycoides in presence of pXO16. We also explored the stability of pXO16 at different temperatures as some B. cereus group members are well-known for their psychro- or thermo-tolerance. This shed light on the thermo-sensitivity of the plasmid. The influence of pXO16 on its host cell growth and on swimming capacity also revealed no or limited impact on its natural host B. thuringiensis sv. israelensis. On the contrary, pXO16 affected more strongly both the growth and swimming capacity of other B. cereus s.l. hosts. This reinforced the running hypothesis of a co-evolution between pXO16 and B. thuringiensis sv. israelensis, enabling the plasmid maintenance without impairing the host strain development.

EcoPhysioMechanics: Integrating energetics and biomechanics to understand fish locomotion under climate change.

Ecological physiologists and biomechanists have investigated swimming performance in a diversity of fishes; however, the connection between form, function, and energetics of locomotion has been rarely evaluated in the same system and under climate change scenarios. In this perspective, I argue that working within the framework of “EcoPhysioMechanics,” i.e. integrating energetics and biomechanics tools, to measure locomotor performance and behavior under different abiotic factors, improves our understanding of the mechanisms, limits and costs of movement. To demonstrate how EcoPhysioMechanics can be applied to locomotor studies, I outline how linking biomechanics and physiology allows us to understand how fishes may modulate their movement to achieve high speeds or reduce the costs of locomotion. I also discuss how the framework is necessary to quantify swimming capacity under climate change scenarios. Finally, I discuss current dearth of integrative studies and gaps in empirical datasets that are necessary to understand fish swimming under changing environments.

Characterization of the pathogenicity of a Bacillus cereus isolate from the Mariana Trench

ABSTRACT Bacillus cereus is an important opportunistic pathogen widely distributed in the environment. In this study, we reported the isolation and characterization of a B. cereus isolate, MB1, from the Challenger Deep of the Mariana Trench. MB1 is aerobic, motile, and able to form endospores. It possesses 5966 genes distributed on a circular chromosome and two plasmids. The MB1 genome contains 14 sets of 23S, 5S, and 16S ribosomal RNA operons, 106 tRNA genes, 4 sRNA genes, 12 genomic islands, 13 prophages, and 302 putative virulence genes, including enterotoxins and cytolysins. Infection studies showed that MB1 was able to cause acute and lethal infection in fish and mice, and was highly toxic to mammalian cells. MB1 induced, in a dose-dependent manner, pyroptotic cell death, characterized by activation of caspase-1, cleavage of gasdermin D, and release of IL-1β and IL-18. MB1 spores exhibited swimming and haemolytic capacity, but were severely attenuated in pathogenicity, which, however, was regained to the full extent when the spores germinated under suitable conditions. Taken together, these results provide new insights into the biological and pathogenic mechanism of deep sea B. cereus.

Multiscale effects of wind‐induced hydrodynamics on lake plankton distribution

AbstractIn this study, we used a combination of high‐intensity sampling technologies, and a 3D hydrodynamic model of a medium‐sized lake in southern Ontario, Canada to investigate physical–biological relationships at spatial scales from 100 m to 6 km and temporal scales from hours to months. At the scale of the whole study basin, we predicted that stronger winds would lead to higher zooplankton biomass downwind relative to upwind. The hydrodynamic model suggests rapid downwind displacement of progressively deeper surface mixed layers with increasing winds, and we found a statistically higher downwind biomass of small‐bodied zooplankton on windy days, but not large zooplankton. At a fine spatial scale (hundreds of meters), we predicted that zooplankton patchiness would decrease with increasing wind mixing of the upper water column and confirmed this for small‐bodied but not large‐bodied zooplankton. At this fine‐scale cross‐correlations of zooplankton biomass with water temperature and chlorophyll fluorescence suggested that zooplankton are not simply moved passively by water masses. We also found a clear change in the cross‐correlation between large‐ and small‐bodied zooplankton biomass, with out‐of‐phase spatial distributions during calm periods becoming in‐phase with increasing winds. Overall these results indicate that the response of zooplankton to wind‐driven physical forces is strongly dependent on an interaction between their body size, which determines their swimming speed and capacity to position themselves vertically in the water column, and the spatial scale and intensity of the wind‐generated physical forces. We discuss the implications for food web interactions.

Numerical Study of Vertical Slot Fishway Flow with Supplementary Cylinders

The vertical slot fishway (VSF) is one of the most common types of fishway facilitating migratory fish movement past obstacles in rivers, such as dams. The uniform vertical distribution of velocity is friendly to fishes with different depth preferences, but unfriendly to fishes with different swimming capacities. For an established VSF, the insertion of an additional structure is a more convenient and effective way to change the flow field rather than altering the original elements. Numerical experiments were carried out using large-eddy simulation (LES) to optimize a typical VSF with supplementary cylinders for fishes with low swimming capacity. The computational domain of the original design is idealized as a box including two pairs of baffles with the periodic boundary condition used in the streamwise direction. The numerical model is well validated by comparison of time-averaged velocity and turbulence kinetic energy with the ADV measurements at gauging points and lines. Two arrangements of cylinders with different numbers and diameters were investigated and compared with the original design based on the first and second-order hydrodynamic statistics at the half height of the VSF. The insertion of cylinders significantly alters the flow field by introducing a branch path of relatively low-speed current. The arrangement of four slim cylinders slightly outperformed that of one thick cylinder against velocity homogeneity along the minor migration path. Although the turbulence intensity is enhanced due to the additional cylinders, the perturbation on fishes is not significant due to the small size of these vortices.

A High-Fat Diet Induces Muscle Mitochondrial Dysfunction and Impairs Swimming Capacity in Zebrafish: A New Model of Sarcopenic Obesity.

Obesity is a highly prevalent disease that can induce metabolic syndrome and is associated with a greater risk of muscular atrophy. Mitochondria play central roles in regulating the physiological metabolism of skeletal muscle; however, whether a decreased mitochondrial function is associated with impaired muscle function is unclear. In this study, we evaluated the effects of a high-fat diet on muscle mitochondrial function in a zebrafish model of sarcopenic obesity (SOB). In SOB zebrafish, a significant decrease in exercise capacity and skeletal muscle fiber cross-sectional area was detected, accompanied by high expression of the atrophy-related markers Atrogin-1 and muscle RING-finger protein-1. Zebrafish with SOB exhibited inhibition of mitochondrial biogenesis and fatty acid oxidation as well as disruption of mitochondrial fusion and fission in atrophic muscle. Thus, our findings showed that muscle atrophy was associated with SOB-induced mitochondrial dysfunction. Overall, these results showed that the SOB zebrafish model established in this study may provide new insights into the development of therapeutic strategies to manage mitochondria-related muscular atrophy.

Copper II oxide nanoparticles (CuONPs) alter metabolic markers and swimming activity in zebra-fish (Danio rerio)

The present study aimed to compare the metabolic effects caused by using copper oxide nanoparticles with two distinct morphologies nanorods and nanosphere. The CuONPs in the form of nanorods were characterized in the order of 500 nm, on a scale of 20, 100, and 500 nm. Meanwhile, the nanosphere CuONPs were characterized in the order of 5 nm, on a 30 nm scale. The analysis of metabolic rate was performed using the closed respirometry technique, specific ammonia excretion, and swimming ability as biomarkers, the physiological effects on Danio rerio were investigated. For the experiments, 88 fish were used, exposed for 24 h at concentrations of 0, 50, 100, and 200 μg/L of copper oxide nanoparticles in the form of nanospheres and nanorods, respectively. The tests carried out with the nanorods demonstrated metabolic alterations in fish, with an increase of 294% and 321% in the metabolic rate at concentrations of 100 μg/L and 200 μg/L, respectively. Furthermore, there was a decrease in specific ammonia excretion by 34% and 83% and in swimming capacity by 34% and 55% at concentrations of 100 and 200 μg/L, respectively, when compared to the control. The tests performed with nanospheres did not show significant changes compared to the control. These experiments showed that different morphological structures of the same copper oxide nanoparticle caused different effects on fish metabolism. It is concluded that the characterization of nanoparticles is essential to understand their effects on fish, since their structural forms can cause different toxic effects on D. rerio.

Validity of the Swimming Capacities and Anthropometric Indices in Predicting the Long-Term Success of Male Water Polo Players: A Position-Specific Prospective Analysis over a Ten-Year Period.

Long-term predictors of success in water polo are rarely reported. This study aimed to evaluate the position-specific validity of the swimming and anthropometric/body build tests on the prediction of the long-term success of male water polo players. The participants were 85 top-level players observed at baseline (junior level, when they were 17–18 years of age; 35 centers and 50 perimeter players) in tests of swimming capacities (15 m water polo sprint, 25 m sprint, and 100 and 400 m freestyle swimming) and anthropometric/body build indices (body mass, body height, arm span, body mass index, and body fat percentage). Over a period of 10 years, participants’ senior-level success was prospectively observed. Multinomial logistic regression with three levels of criteria (high achievement, medium achievement, and low achievement at the senior level) was applied to identify the predictive validity of the swimming and anthropometric/body build indices. For the total sample (not dividing perimeter from center players), all observed swimming capacities, body height, and arm span were significantly associated with success, with more successful players being taller, with a longer arm span, and superior swimming capacities. Body height and 100 m freestyle swimming were significant predictors of success among centers. Achievement in 100 and 400 m freestyle swimming, body height, and a lower percentage of body fat were correlated with higher senior-level performance in perimeter players. The results showed better validity of the anaerobic-lactate and aerobic swimming tests than sprint swimming in predicting the long-term achievement of male water polo players. Differences in the influence of swimming capacities and body-build indices on senior-level success between observed playing positions are related to differences in game duties, playing time, and consequent metabolic demands.

Influence of cognitive performance and swimming capacities on selection of youth water polo players to national team.

Water-polo is an official competitive olympic sport with high energy and technical-tactical demands. The aim of this study was to evaluate the influence of cognitive performance and specific swimming capacities on the selection of youth water polo players to the national water polo team. There were 83 youth water polo players (mean age 13.61±0.67 years) who attended the Croatian Water Polo Foundation training camps included in this cross-sectional study. Testing included anthropometric measurements, specific swimming capacities and cognitive performance (Stroop test). Among 83 youth water polo players included in this study there were 13 goalkeepers, 13 center-defenders, 13 centers, 31 perimeter players and 13 wings. Selected players (N.=40) performed faster in OffTime (selected 62.99±10.21 s vs. non-selected 69.98±8.93 s, P=0.002) and OnTime (selected 75.61±15.85 s vs. non-selected 86.01±15.40 s, P=0.004) of the Stroop test than non-selected players (N.=43). Logistic regression analysis showed significant association between selection of youth water polo players to the national team and swimming results in 400 m crawl and 100 m crawl, as well as OffTime, OnTime and OnTime minus OffTime on the Stroop test. The results of this study showed that psychomotor ability, inhibition, motor speed and cognitive flexibility were found to be the most important predictors for the selection of youth water polo players to the national water polo team. Furthermore, selected water polo players demonstrated better psychomotor abilities, inhibition, and motor speed, as well as better results in all specific swimming tests in comparison to non-selected players.