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INTRODUCTION: Since sex-specific accumulated oxygen deficit (AOD) during high-intensity swimming remains unstudied, this study aimed to assess AOD during 50, 100, and 200 m front-crawl performances to compare the responses between sexes and analyse the effect of lean body mass (LBM). METHODS: Twenty swimmers (16.2 ± 2.8 years, 61.6 ± 7.8 kg, and 48.8 ± 11.2 kg LBM-50% males) performed 50, 100, and 200 m to determine accumulated oxygen uptake (V̇O2Ac). The swimmers also performed an incremental test from which five submaximal steps were selected to estimate the oxygen demand (V̇O2demand) from the V̇O2 versus velocity adjustment. V̇O2 was sampled using a gas analyser coupled with a respiratory snorkel. AOD was the difference between V̇O2demand and V̇O2Ac, and LBM (i.e. lean mass not including bone mineral content) was assessed by dual-energy X-ray absorptiometry (DXA). RESULTS: A two-way ANOVA evidenced an AOD increase with distance for both sexes: 19.7 ± 2.5 versus 24.9 ± 5.5, 29.8 ± 8.0 versus 36.5 ± 5.8, and 41.5 ± 9.4 versus 5.2 ± 11.9 ml × kg-1, respectively, for 50, 100, and 200 m (with highest values for females, P < 0.01). Inverse correlations were observed between LBM and AOD for 50, 100, and 200 m (r = - 0.60, - 0.38 and - 0.49, P < 0.05). AOD values at 10 and 30 s elapsed times in each trial decreased with distance for both sexes, with values differing when female swimmers were compared to males in the 200 m trial (at 10 s: 2.6 ± 0.6 vs. 3.4 ± 0.6; and at 30 s: 7.9 ± 1.7 vs. 10.0 ± 1.8 ml × kg-1, P < 0.05). CONCLUSION: LBM differences between sexes influenced AOD values during each trial, suggesting that reduced muscle mass in female swimmers plays a role on the higher AOD (i.e. anaerobic energy) demand than males while performing supramaximal trials.

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Functional morphology investigates the relationships between morphological characters and external factors, such as environmental, physical and ecological features. Here, we evaluate the functional relationships between body shape and trophic ecology of a tropical demersal marine fish community using geometric morphometrics techniques and modelling, hypothesizing that shape variables could partially explain fish trophic level. Fish were collected over the continental shelf of northeast Brazil (4-9°S). Analysed fish were distributed into 14 orders, 34 families and 72 species. Each individual was photographed in lateral view, and 18 landmarks were distributed along the body. A principal component analysis (PCA) applied on morphometric indices revealed that fish body elongation and fin base shape were the main axes of variation explaining the morphology. Low trophic levels (herbivore and omnivore) are characterized by deep bodies and longer dorsal and anal fin bases, while predators present elongated bodies and narrow fin bases. Fin position (dorsal and anal fins) on the fish body is another important factor contributing to (i) body stability at high velocity (top predators) or (ii) manoeuvrability (low trophic levels). Using multiple linear regression, we verified that 46% of trophic level variability could be explained by morphometric variables, with trophic level increasing with body elongation and size. Interestingly, intermediate trophic categories (e.g., low predators) presented morphological divergence for a given trophic level. Our results, which can likely be expanded to other tropical and nontropical systems, show that morphometric approaches can provide important insights into fish functional characteristics, especially in trophic ecology.

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This study assessed the energy cost in swimming (C) during short and middle distances to analyze the sex-specific responses of C during supramaximal velocity and whether body composition account to the expected differences. Twenty-six swimmers (13 men and 13 women: 16.7 ± 1.9 vs. 15.5 ± 2.8 years old and 70.8 ± 10.6 vs. 55.9 ± 7.0 kg of weight) performed maximal front crawl swimming trials in 50, 100, and 200 m. The oxygen uptake ( V ˙ O2) was analyzed along with the tests (and post-exercise) through a portable gas analyser connected to a respiratory snorkel. Blood samples were collected before and after exercise (at the 1st, 3rd, 5th, and 7th min) to determine blood lactate concentration [La-]. The lean mass of the trunk (LM Trunk ), upper limb (LM UL ), and lower limb (LM LL ) was assessed using dual X-ray energy absorptiometry. Anaerobic energy demand was calculated from the phosphagen and glycolytic components, with the first corresponding to the fast component of the V ˙ O2 bi-exponential recovery phase and the second from the 2.72 ml × kg-1 equivalent for each 1.0 mmol × L-1 [La-] variation above the baseline value. The aerobic demand was obtained from the integral value of the V ˙ O2 vs. swimming time curve. The C was estimated by the rate between total energy releasing (in Joules) and swimming velocity. The sex effect on C for each swimming trial was verified by the two-way ANOVA (Bonferroni post hoc test) and the relationships between LM Trunk , LM UL , and LM LL to C were tested by Pearson coefficient. The C was higher for men than women in 50 (1.8 ± 0.3 vs. 1.3 ± 0.3 kJ × m-1), 100 (1.4 ± 0.1 vs. 1.0 ± 0.2 kJ × m-1), and 200 m (1.0 ± 0.2 vs. 0.8 ± 0.1 kJ × m-1) with p < 0.01 for all comparisons. In addition, C differed between distances for each sex (p < 0.01). The regional LM Trunk (26.5 ± 3.6 vs. 20.1 ± 2.6 kg), LM UL (6.8 ± 1.0 vs. 4.3 ± 0.8 kg), and LM LL (20.4 ± 2.6 vs. 13.6 ± 2.5 kg) for men vs. women were significantly correlated to C in 50 (R 2 adj = 0.73), 100 (R 2 adj = 0.61), and 200 m (R 2 adj = 0.60, p < 0.01). Therefore, the increase in C with distance is higher for men than women and is determined by the lean mass in trunk and upper and lower limbs independent of the differences in body composition between sexes.

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The purpose of this study is to know the effect of temperature on fish muscle contraction of jack mackerel (Trachurus japonicus), which muscle contraction will determine the tail beat frequency and maximum swimming speed. The maximum swimming speed of was evaluated according to the measurement of the muscle contraction time with electric stimuli of 2-7 V, 50 ms. Fish were separated into four groups for temperature acclimation at 10, 15, 18 and 22ºC to reflect typical changes in seasonal water temperature in Japan. Results showed that the swimming speed of the fish was positively related to the tail-beat frequency at all temperatures. The muscle contraction time was also affected by the acclimated temperature, which longer at the lower temperature than higher ones. Mean contraction time (Tm) was 45.1 ms at 10 ºC, 32.7 ms at 15 ºC, 32.9 ms at 18 ºC, and 31.9 ms at 22 ºC, respectively. The mean of maximum tail-beat frequency (Fmax) obtained from Fmax = ½ Tm was 11.4 Hz at 10 ºC, 15.8 Hz at 15 ºC, 16,4 Hz at 18 ºC, and 16.6 Hz at 22 ºC. These were used to estimate the maximum swimming speed (Umax) at each temperature, resulting in 9.45 FL s-¹ at 10 ºC, 13.5 FL s-¹ at 15 ºC, 14.0 FL s-¹ 18 ºC, and 14.2 FL s-¹ at 22 ºC. The seasonal temperature effects on the swimming performance of T. japonicus, which lower water temperature in the winter made low swimming performance.

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The purpose of this study is to know the effect of temperature on fish muscle contraction of jack mackerel (Trachurus japonicus), which muscle contraction will determine the tail beat frequency and maximum swimming speed. The maximum swimming speed of was evaluated according to the measurement of the muscle contraction time with electric stimuli of 2-7 V, 50 ms. Fish were separated into four groups for temperature acclimation at 10, 15, 18 and 22ºC to reflect typical changes in seasonal water temperature in Japan. Results showed that the swimming speed of the fish was positively related to the tail-beat frequency at all temperatures. The muscle contraction time was also affected by the acclimated temperature, which longer at the lower temperature than higher ones. Mean contraction time (Tm) was 45.1 ms at 10 ºC, 32.7 ms at 15 ºC, 32.9 ms at 18 ºC, and 31.9 ms at 22 ºC, respectively. The mean of maximum tail-beat frequency (Fmax) obtained from Fmax = ½ Tm was 11.4 Hz at 10 ºC, 15.8 Hz at 15 ºC, 16,4 Hz at 18 ºC, and 16.6 Hz at 22 ºC. These were used to estimate the maximum swimming speed (Umax) at each temperature, resulting in 9.45 FL s-¹ at 10 ºC, 13.5 FL s-¹ at 15 ºC, 14.0 FL s-¹ 18 ºC, and 14.2 FL s-¹ at 22 ºC. The seasonal temperature effects on the swimming performance of T. japonicus, which lower water temperature in the winter made low swimming performance.(AU)

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Sympatric speciation occurs without geographical barriers and is thought to often be driven by ecological specialization of individuals that eventually diverge genetically and phenotypically. Distinct morphologies between sympatric populations occupying different niches have been interpreted as such differentiating adaptive phenotypes, yet differences in performance and thus likely adaptiveness between them were rarely tested. Here, we investigated if divergent body shapes of two sympatric crater lake cichlid species from Nicaragua, one being a shore-associated (benthic) species while the other prefers the open water zones (limnetic), affect cruising (Ucrit ) and sprinting (Usprint ) swimming abilities - performances particularly relevant to their respective lifestyles. Furthermore, we investigated species differences in oxygen consumption (MO2 ) across different swimming speeds and compare gene expression in gills and white muscle at rest and during exercise. We found a superior cruising ability in the limnetic Amphilophus zaliosus compared to the benthic Amphilophus astorquii, while sprinting was not different, suggesting that their distinct morphologies affect swimming performance. Increased cruising swimming ability in A. zaliosus was linked to a higher oxygen demand during activity (but not rest), indicating different metabolic rates during exercise - a hypothesis supported by coinciding gene expression patterns of gill transcriptomes. We identified differentially expressed genes linked to swimming physiology, regulation of swimming behaviour and oxygen intake. A combination of physiological and morphological differences may thus underlie adaptations to these species' distinct niches. This complex ecological specialization probably resulted in morphological and physiological trade-offs that contributed to the rapid establishment and maintenance of divergence with gene flow.

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Local anaesthetics are among the most used drugs in clinical practice, but once they are released to the environment, the effects on the aquatic fauna remain uncertain. This study evaluates, for the first time, the impact of tetracaine, lidocaine and bupivacaine on the survival rate and physiological effects of cladocera Daphnia magna. Video-tracking and image processing allowed us to obtain changes in behaviour parameters like swimming average velocity and mean square displacement. We found that tetracaine shows the most severe effect. A high-speed microscopy system was also used to determine the response of D. magna heart to these drugs. Our results show that tetracaine presents dose-dependent area reduction during all cardiac cycle, while bupivacaine and lidocaine did not present significative effects on heart size. The tested drugs, at environmental high concentrations, altered behaviour, heart function and survival of D. magna.

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BACKGROUND: In the wild, matrinchã (Brycon amazonicus) and tambaqui (Colossoma macropomum) rely strongly on their swimming capacity to perform feeding, migration and reproductive activities. Sustained swimming speed in fishes is performed almost exclusively by aerobic red muscles. The white muscle has high contraction power, but fatigue quickly, being used mainly in sprints and bursts, with a maximum duration of few seconds. The Ucrit test, an incremental velocity procedure, is mainly a measure of the aerobic capacity of a fish, but with a high participation of anaerobic metabolism close to the velocity of fatigue. Our previous study has indicated a high swimming performance of matrinchã (Ucrit) after hypoxia exposure, despite increased levels of lactate in plasma. In contrast, tambaqui with high lactate levels in plasma presented very low swimming performance. Therefore, we aimed to study the resistance of matrinchã and tambaqui to the increased lactate levels in muscle over an incremental velocity test (Ucrit). As a secondary aim, we analyzed the differences in anaerobic metabolism in response to environmental hypoxia, which could also support the better swimming performance of matrinchã, compared to tambaqui. METHODS: We measured, over incremented velocities in both species, the metabolic rate (the oxygen consumption by the fish; MO2), and the concentrations of lactate and nitrites and nitrates (NOx) in muscles. NOx was measured as an indicator of nitric oxide and its possible role in improving cardiorespiratory capacity in these fishes, which could postpone the use of anaerobic metabolism and lactate production during the swimming test. Also, we submitted fishes until fatigue and hypoxia (0.5 mg L-1) and measured, in addition to the previous parameters, lactate dehydrogenase activity (LDH; the enzyme responsible for lactate production), since that swimming performance could also be explained by the anaerobic capacity of producing ATP. RESULTS: Matrinchã exhibited a better swimming performance and higher oxygen consumption rates. Lactate levels were higher in matrinchã only at the moment of fatigue. Under hypoxia, LDH activity increased in the white muscle only in tambaqui, but averages were always higher in matrinchã. DISCUSSION AND CONCLUSIONS: The results suggest that matrinchã is more resistant than tambaqui regarding lactate accumulation in muscle at the Ucrit test, but it is not clear how much it contributes to postpone fatigue. The higher metabolic rate possibly allows the accumulated lactate to be used as aerobic fuel by the matrinchã, improving swimming performance. More studies are needed regarding matrinchã's ability to oxidize lactate, the effects of exercise on muscle acidification, and the hydrodynamics of these species, to clarify why matrinchã is a better swimmer than tambaqui.

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The larval ultrastructure of Brycon gouldingi related to swimming and feeding from hatching to total yolk absorption is described from scanning electron micrographs. Newly hatched larvae (time zero) had no mouth opening, undefined optic vesicles, an olfactory plate visible as a shallow depression, rudimentary gill arches, neural groove, embryonic fin and a primary neuromast in the dorsal region of the head. At the time of yolk absorption, 55 h post hatching, the larvae presented an optic vesicle comprising an optic cup and crystalline lens; a mouth with tongue, tapered teeth and taste buds; a ciliated olfactory cavity; branched gill arches; filled neural groove signalling central nervous system development; caudal, pectoral, dorsal and anal fins; and neuromasts distributed throughout the head and body. These characters are related to prey capture and swimming ability, key aspects of survival during the larval stage. The results of this study provide important information for exploitation and aquaculture of B. gouldingi.

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Most studies of predator-induced plasticity have focused on documenting how prey species respond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleurodema thaul tadpoles exposed to the dragonfly Rhionaeschna variegata responded strongly by showing morphological changes, less activity, and better survival than non-exposed tadpoles. Here, we tested whether there is a functional link between morphological plasticity and increased survival in the presence of predators. Tadpoles that experienced predation risk were smaller, less developed, and much less active than tadpoles without this experience. Burst speed did not correlate significantly with morphological changes and predator-induced deeper tails did not act as a lure to divert predator strikes away from the head. Although we have previously found that tadpoles with predator-induced morphology survive better under a direct predator threat, our results on the functional link between morphology and fitness are not conclusive. Our results suggest that in P. thaul tadpoles (1) burst speed is not important to evade predators, (2) those exposed to predators reduce their activity, and (3) morphological changes do not divert predator attacks away from areas that compromise tadpole survivalEE. Our results show that morphological changes in P. thaul tadpoles do not explain burst speed or lure attraction, although there was a clear reduction of activity, which itself reduces predation. We propose that changes in tadpole activity could be further analyzed from another perspective, with morphological change as an indirect product of behavior mediated by physiological mechanisms.

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Although consistent individual-level differences in behaviour are widespread and potentially important in evolutionary and ecological processes, relatively few studies focus on the physiological mechanisms that might underlie and regulate these individual-level differences in wild populations. We conducted experiments to determine whether checkered pufferfish (Sphoeroides testudineus), which were collected from a dynamic (in terms of depth and water temperature) tidal mangrove creek environment in The Bahamas, have consistent individual-level differences in locomotor activity and the response to a simulated predator threat, as well as swimming performance and puffing in response to stressors. The relationships between personality and performance traits were evaluated to determine whether they represented stress-coping styles or syndromes. Subsequently, a displacement study was conducted to determine how personality and performance in the laboratory compared to movements in the field. In addition, we tested whether a physiological dose of the stress hormone cortisol would alter individual consistency in behavioural and performance traits. We found that pufferfish exhibited consistent individual differences in personality traits over time (e.g., activity and the duration of a response to a threat) and that performance was consistent between the lab and the natural enclosure. Locomotor activity and the duration of startled behaviour were not associated with swimming and puffing performance. Locomotor activity, puffing performance, and swimming performance were not related to whether fish returned to the tidal creek of capture after displacement. Similarly, a cortisol treatment did not modify behaviour or performance in the laboratory. The results reveal that consistent individual-level differences in behaviour and performance were present in a population from a fluctuating and physiologically challenging environment but that such traits are not necessarily correlated. We also determined that certain individual performance traits were repeatable between the lab and a natural enclosure. However, we found no evidence of a relationship between exogenous cortisol levels and behavioural traits or performance in these fish, which suggests that other internal and external mechanisms may underlie the behaviours and performance tested.

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Tadpoles of two sympatric anurans, Bufo gargarizans Cantor, 1842 and Rana zhenhaiensis Ye, Fei & Matsui, 1995, were used as model organisms to examine the effects of different levels of tail loss on swimming performance and survival. On average, B. gargarizans tadpoles were shorter and had smaller tails and body mass than R. zhenhaiensis. After 75% tail loss, the survival rate of experimental and control B. gargarizans tadpoles, and of experimental tadpoles of the two species, differed significantly; the number of tadpoles surviving a complete impairment of their swimming ability did not differ between B. gargarizans and R. zhenhaiensis. After 50% tail loss, the swimming performance (swimming speed, maximum distance and number of stops) of the two species was significantly affected. However, the adverse influence of tail loss on the swimming speed of B. gargarizans tadpoles was greater compared to R. zhenhaiensis tadpoles. Our data indicates that a 50% tail loss results in swimming costs for B. gargarizans and R. zhenhaiensis tadpoles, and that 75% tail loss decreases the survival rate of B. gargarizans tadpoles. Therefore, we conclude that tadpoles of different species and with the same degree of tail loss use distinctive strategies to improve individual fitness in the face of predator pressure.

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Tadpoles of two sympatric anurans, Bufo gargarizans Cantor, 1842 and Rana zhenhaiensis Ye, Fei & Matsui, 1995, were used as model organisms to examine the effects of different levels of tail loss on swimming performance and survival. On average, B. gargarizans tadpoles were shorter and had smaller tails and body mass than R. zhenhaiensis. After 75% tail loss, the survival rate of experimental and control B. gargarizans tadpoles, and of experimental tadpoles of the two species, differed significantly; the number of tadpoles surviving a complete impairment of their swimming ability did not differ between B. gargarizans and R. zhenhaiensis. After 50% tail loss, the swimming performance (swimming speed, maximum distance and number of stops) of the two species was significantly affected. However, the adverse influence of tail loss on the swimming speed of B. gargarizans tadpoles was greater compared to R. zhenhaiensis tadpoles. Our data indicates that a 50% tail loss results in swimming costs for B. gargarizans and R. zhenhaiensis tadpoles, and that 75% tail loss decreases the survival rate of B. gargarizans tadpoles. Therefore, we conclude that tadpoles of different species and with the same degree of tail loss use distinctive strategies to improve individual fitness in the face of predator pressure.(AU)

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This study characterized the morphological differences among migratory fish species from the Paraná River Basin. A total of 177 adult fish of Leporinus elongatus, Leporinus macrocephalus, Prochilodus lineatus, Salminus brasiliensis, Pimelodus maculatus, Pinirampus pirinampu, Pseudoplatystoma corruscans, Pterodoras granulosus, and Rhaphiodon vulpinus were sampled in the Canal da Piracema, a fish passage system at Itaipu Dam, Paraná River. The migratory species were analyzed through 22 morphometric measurements and fineness ratio to identify morphological patterns related to swimming performance. Four species groups were indicated by the Cluster analysis: I) R. vulpinus; II) P. corruscans; III) L. macrocephalus, L. elongatus, P. lineatus, P. maculatus, and S. brasiliensis - measurements of head height and anal fin length formed this group; and IV) P. granulosus and P. pirinampu - measurements of maximum body width and caudal peduncle width contributed to form this group. The morphometric variables that most contributed to the distinction were head length and mouth width for groups I and II. The species R. vulpinus and P. granulosus differed from other species, showing fineness ratios of 9.4 and 3.7, respectively. Leporinus elongatus, L. macrocephalus, P. lineatus, P. maculatus, and S. brasiliensis showed significant differences from other species, with ratios ranging from 4.57 to 5.19, indicating that these species may be better swimmers. Long-distance migratory species using the Piracema Canal to ascend upstream areas differed morphologically, morphological characteristics such as a narrow caudal peduncle and maximum body length, besides to the values of the fineness ratio, were essential to differentiate the migratory species.

Este estudo caracterizou as diferenças morfológicas entre espécies de peixes migradores da bacia do rio Paraná. Um total de 117 peixes adultos das espécies Leporinus elongatus, Leporinus macrocephalus, Prochilodus lineatus, Salminus brasiliensis, Pimelodus maculatus, Pinirampus pirinampu, Pseudoplatystoma corruscans, Pterodoras granulosus e Rhaphiodon vulpinus foram capturados no Canal da Piracema, um sistema de transposição para peixes na barragem de Itaipu, rio Paraná. As espécies migradoras foram analisadas através de 22 medidas morfométricas e razão fineza para identificar padrões morfológicos relacionados à capacidade natatória. Quatro grupos de espécies foram evidenciados pela Análise de Cluster: I) R. vulpinus; II) P. corruscans; III) L. macrocephalus, L. elongatus, P. lineatus, P. maculatus e S. brasiliensis, medidas de altura de cabeça e comprimento da nadadeira anal formaram este grupo; e IV) P. granulosus e P. pirinampu - medidas de largura máxima do corpo e largura do pedúnculo caudal contribuíram para a formação deste grupo. As variáveis morfométricas que mais contribuíram para distinção dos grupos I e II foram comprimento da cabeça e largura da boca. As espécies R. vulpinus e P. granulosus diferiram das demais, apresentando razão de fineza de 9,4 e 3,7, respectivamente. Leporinus elongatus, L. macrocephalus, P. lineatus, P. maculatus, S. brasiliensis diferiram significativamente das demais espécies com valores de razão fineza que variaram entre 4,57 a 5,19, indicando que estas espécies podem apresentar melhor desempenho natatório. As espécies migradoras de longa distância que utilizam o Canal da Piracema para ascender áreas a montante diferiram morfologicamente, características morfológicas como pedúnculo caudal estreito e largura máxima do corpo, bem como os valores de razão de fineza foram determinantes na diferenciação das espécies aqui analisadas.

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This paper presents results of a fishway evaluation performed at the Engenheiro Sérgio Motta Hydroelectric Power Plant (known as Porto Primavera) - CESP, Paraná River, Brazil. The evaluation was designed to quantify entry and passage proportions of 4 long-distance migratory fish species: Brycon orbignyanus (piracanjuba), Piaractus mesopotamicus (pacu), Prochilodus lineatus (curimba), and Rhinelepis aspera (cascudo-preto). Proportions finding and entering the fishway differed between species, ranged from 7.4 % (Prochilodus lineatus) to 55.4% (Piaractus mesopotamicus). Also, proportion passing was different between species, ranged from 31% (R. aspera) to 100% (Prochilodus lineatus). Fish that were marked and released within the fishway had greater failure rates than those that entered volitionally. Total time to pass ranged from 1.48 hours (Prochilodus lineatus) to 178.9 hours (R. aspera). Failure rates were greatest in the lower end of the fishway. Although some individuals of all species passed successfully, significant challenges remain to restoring connectivity of the upper Paraná River.(AU)

Este artigo apresenta resultados da avaliação de passagem de peixes na escada localizada na Usina Hidrelétrica Engenheiro Sérgio Motta - CESP (rio Paraná, Porto Primavera, Brasil). A avaliação foi concebida para quantificar a entrada e proporções de passagem de quatro espécies de peixes migradores de longa distância: Brycon orbignyanus (piracanjuba), Piaractus mesopotamicus (pacu), Prochilodus lineatus (curimba) e Rhinelepis aspera (cascudo-preto). As proporções de encontrar e entrar na escada variaram de 7,4% (Prochilodus lineatus) para 55,4% (Piaractus mesopotamicus). A proporção de passagem através da escada variou de 31% (R. aspera) a 100% (Prochilodus lineatus). Os peixes que foram marcados e soltos no interior da escada apresentaram taxas maiores de falha do que aqueles que entraram voluntariamente. O tempo médio para passar variou de 1,48 horas (Prochilodus lineatus) para 178,9 horas (R. aspera). A taxa de falha foi maior no extremo inferior da passagem para peixes. Embora alguns indivíduos de todas as espécies passaram com sucesso, desafios significantes permanecem para restaurar a conectividade do alto rio Paraná.(AU)

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This study investigated the external body morphology (based on morphometric data) and the swimming efficiency in fish passages (based on the ascent time in a fish ladder) of two Neotropical long-distance migratory species. The fish were collected in the fish ladder of the Porto Primavera Hydroelectric Power Plant (known as Engenheiro Sergio Motta), upper Paraná River, Brazil. The species differ in several morphometric ratios related to swimming performance. Prochilodus lineatus exhibited a higher muscle ratio and caudal fin length ratio. However, Leporinus elongatus showed higher values for the fineness ratio, a higher length from snout to pectoral fin base ratio, and a higher caudal peduncle depth factor. Although both species show good swimming performance, the characteristics listed above may enable L. elongatus to apply greater power and propulsion, allowing it to reach a high swimming speed and to exhibit greater efficiency than P. lineatus. Leporinus elongatus moves faster than P. lineatus and has a lower mean ascent time (1.39 hours) than P. lineatus (3.76 hours). Prochilodus lineatus would require a somewhat longer time to pass through the fish ladder.(AU)

Este estudo investigou a relação entre a morfologia externa do corpo (baseado em dados morfométricos) e eficiência de natação em passagem para peixes (baseado no tempo de ascensão em uma escada para peixes) de duas espécies neotropicais migradoras de longas distâncias. Os peixes foram coletados na escada para peixes da Usina Hidrelétrica de Porto Primavera (conhecida como Engenheiro Sérgio Motta), alto Rio Paraná, Brasil. As espécies diferem em algumas razões morfométricas referentes ao desempenho de natação: Prochilodus lineatus apresentou valores mais elevados para razão muscular e razão do comprimento da nadadeira caudal. No entanto, Leporinus elongatus apresentou valores mais elevados para razão fineza, para razão do comprimento do focinho à base da nadadeira peitoral e para fator de largura do pedúnculo caudal. Embora ambas as espécies tenham um bom desempenho natatório, essas características podem permitir a L. elongatus aplicar uma maior potência e propulsão, permitindo atingir velocidades de natação elevadas e apresentar uma melhor eficiência em relação a P. Lineatus. Leporinus elongatus movimenta-se mais rápido, com um tempo médio de ascensão (1,39 horas) inferior ao de P. lineatus (3,76 horas), que requer um tempo um pouco maior para passar através da escada para peixes.(AU)

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This paper presents results of a fishway evaluation performed at the Engenheiro Sérgio Motta Hydroelectric Power Plant (known as Porto Primavera) - CESP, Paraná River, Brazil. The evaluation was designed to quantify entry and passage proportions of 4 long-distance migratory fish species: Brycon orbignyanus (piracanjuba), Piaractus mesopotamicus (pacu), Prochilodus lineatus (curimba), and Rhinelepis aspera (cascudo-preto). Proportions finding and entering the fishway differed between species, ranged from 7.4 % (Prochilodus lineatus) to 55.4% (Piaractus mesopotamicus). Also, proportion passing was different between species, ranged from 31% (R. aspera) to 100% (Prochilodus lineatus). Fish that were marked and released within the fishway had greater failure rates than those that entered volitionally. Total time to pass ranged from 1.48 hours (Prochilodus lineatus) to 178.9 hours (R. aspera). Failure rates were greatest in the lower end of the fishway. Although some individuals of all species passed successfully, significant challenges remain to restoring connectivity of the upper Paraná River.

Este artigo apresenta resultados da avaliação de passagem de peixes na escada localizada na Usina Hidrelétrica Engenheiro Sérgio Motta - CESP (rio Paraná, Porto Primavera, Brasil). A avaliação foi concebida para quantificar a entrada e proporções de passagem de quatro espécies de peixes migradores de longa distância: Brycon orbignyanus (piracanjuba), Piaractus mesopotamicus (pacu), Prochilodus lineatus (curimba) e Rhinelepis aspera (cascudo-preto). As proporções de encontrar e entrar na escada variaram de 7,4% (Prochilodus lineatus) para 55,4% (Piaractus mesopotamicus). A proporção de passagem através da escada variou de 31% (R. aspera) a 100% (Prochilodus lineatus). Os peixes que foram marcados e soltos no interior da escada apresentaram taxas maiores de falha do que aqueles que entraram voluntariamente. O tempo médio para passar variou de 1,48 horas (Prochilodus lineatus) para 178,9 horas (R. aspera). A taxa de falha foi maior no extremo inferior da passagem para peixes. Embora alguns indivíduos de todas as espécies passaram com sucesso, desafios significantes permanecem para restaurar a conectividade do alto rio Paraná.

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RESUMO

This study investigated the external body morphology (based on morphometric data) and the swimming efficiency in fish passages (based on the ascent time in a fish ladder) of two Neotropical long-distance migratory species. The fish were collected in the fish ladder of the Porto Primavera Hydroelectric Power Plant (known as Engenheiro Sergio Motta), upper Paraná River, Brazil. The species differ in several morphometric ratios related to swimming performance. Prochilodus lineatus exhibited a higher muscle ratio and caudal fin length ratio. However, Leporinus elongatus showed higher values for the fineness ratio, a higher length from snout to pectoral fin base ratio, and a higher caudal peduncle depth factor. Although both species show good swimming performance, the characteristics listed above may enable L. elongatus to apply greater power and propulsion, allowing it to reach a high swimming speed and to exhibit greater efficiency than P. lineatus. Leporinus elongatus moves faster than P. lineatus and has a lower mean ascent time (1.39 hours) than P. lineatus (3.76 hours). Prochilodus lineatus would require a somewhat longer time to pass through the fish ladder.

Este estudo investigou a relação entre a morfologia externa do corpo (baseado em dados morfométricos) e eficiência de natação em passagem para peixes (baseado no tempo de ascensão em uma escada para peixes) de duas espécies neotropicais migradoras de longas distâncias. Os peixes foram coletados na escada para peixes da Usina Hidrelétrica de Porto Primavera (conhecida como Engenheiro Sérgio Motta), alto Rio Paraná, Brasil. As espécies diferem em algumas razões morfométricas referentes ao desempenho de natação: Prochilodus lineatus apresentou valores mais elevados para razão muscular e razão do comprimento da nadadeira caudal. No entanto, Leporinus elongatus apresentou valores mais elevados para razão fineza, para razão do comprimento do focinho à base da nadadeira peitoral e para fator de largura do pedúnculo caudal. Embora ambas as espécies tenham um bom desempenho natatório, essas características podem permitir a L. elongatus aplicar uma maior potência e propulsão, permitindo atingir velocidades de natação elevadas e apresentar uma melhor eficiência em relação a P. Lineatus. Leporinus elongatus movimenta-se mais rápido, com um tempo médio de ascensão (1,39 horas) inferior ao de P. lineatus (3,76 horas), que requer um tempo um pouco maior para passar através da escada para peixes.

Assuntos

RESUMO

A primeira resposta ao estresse é a fuga, que depende do desempenho natatório e de ajustes fisiológicos. Este estudo investigou a velocidade crítica de natação (Ucrit) de matrinxã após exposição à hipoxia. Para isso, os peixes foram expostos à hipoxia, sendo uma parte do grupo analisada antes e outra após natação forçada, por meio da Ucrit. A hipoxia resultou no aumento de lactato, glicose, cortisol e hematócrito. Mudanças nos níveis de sódio e potássio, bem como os valores de Ucrit não foram observadas. Sugere-se que o matrinxã seja sensível à hipoxia, mas os ajustes fisiológicos são suficientes para manter seu desempenho natatório.

Escape is the first response of fish to stress, that depends on the swimming performance and the physiological adjustments. This study has investigated the critical swimming speed (Ucrit) of matrinxã after exposure to hypoxia. To achieve that, the fishes were exposed to hypoxia and analyzed before and after forced swimming, using Ucrit. The hypoxia caused an increase of lactate, glucose, cortisol and hematocrit. No changes of plasma sodium and potassium levels, as well as the Ucrit, were observed. We suggest that matrinxã is sensitive to hypoxia, but the physiological adjustments are sufficient to keep its swimming performance.

Assuntos

RESUMO

Escape is the first response of fish to stress, that depends on the swimming performance and the physiological adjustments. This study has investigated the critical swimming speed (Ucrit) of matrinxã after exposure to hypoxia. To achieve that, the fishes were exposed to hypoxia and analyzed before and after forced swimming, using Ucrit. The hypoxia caused an increase of lactate, glucose, cortisol and hematocrit. No changes of plasma sodium and potassium levels, as well as the Ucrit, were observed. We suggest that matrinxã is sensitive to hypoxia, but the physiological adjustments are sufficient to keep its swimming performance.

A primeira resposta ao estresse é a fuga, que depende do desempenho natatório e de ajustes fisiológicos. Este estudo investigou a velocidade crítica de natação (Ucrit) de matrinxã após exposição à hipoxia. Para isso, os peixes foram expostos à hipoxia, sendo uma parte do grupo analisada antes e outra após natação forçada, por meio da Ucrit. A hipoxia resultou no aumento de lactato, glicose, cortisol e hematócrito. Mudanças nos níveis de sódio e potássio, bem como os valores de Ucrit não foram observadas. Sugere-se que o matrinxã seja sensível à hipoxia, mas os ajustes fisiológicos são suficientes para manter seu desempenho natatório.