Swimming Ability Of Fish Research Articles

Reservoir Operating Rules to Create Effective Fish Migration Passages in a Reservoir

AbstractLow flow velocity disrupts the potential fish migration passages in a reservoir, and causes reservoirs to become labyrinths for migratory fish. Previous studies showed that fish migration passages in a reservoir can be restored by modifying reservoir operation. However, reservoir operating rules that are specifically designed to support fish migration have not been established, leading to low success for fish migration and high socioeconomic losses. In this research, we established new reservoir operating rules to improve the migration success rate while also reducing socioeconomic losses. Under the new rules, two parameters (reservoir water level and predicted reservoir inflows) were adapted to trigger water releases to open migration passages. The two parameters were optimized by considering hydrological processes, fish migration processes below the dam, the swimming ability of fish, and the socioeconomic benefits provided by the reservoir. We used data from China's Danjiangkou Reservoir to test the effectiveness of the proposed method. We found that the new method can not only improve the migration success rate (from 0.1% to 4.2%), but can also slightly reduce the reservoir's socioeconomic losses (by 3.7%–7.0%). The new method effectively balances the needs of fish migration with the need for socioeconomic development in the areas surrounding dammed rivers.

Morphology and motor behavior of endemic fishes in the upper reaches of the Yangtze River basin.

Dam construction alters the hydrodynamic conditions, consequently impacting the swimming behavior of fish. To explore the effect of flow hydrodynamics on fish swimming behavior, five endemic fish species in the upper Yangtze River basin were selected. Through high-speed video visualization and computer analysis, these species' swimming patterns under different flow velocities (0.1-1.2 m/s) were investigated. The kinematic and morphological characteristics of the fish were presented. The principal component analysis was used to analyse the main factors influencing the swimming ability of fish and to determine the correlation coefficients among fish behavior indicators. Fish exhibited three different swimming patterns under different flow velocities. Low velocity (0.1-0.3 m/s) corresponds to free motion, middle velocity (0.4-0.7 m/s) corresponds to cruising motion, and high velocity corresponds to stress motion (0.8-1.2 m/s). The fish kinematic index curves were obtained, and four of five fish species showed two extreme points, which means the optimal and adverse swimming strategies can be determined. With the increase in flow velocity, the tail-beat frequency showed an increasing trend, whereas the tail-beat angle and amplitude showed a decreasing trend. Morphological and kinematic parameters were the two main indexes that affect the swimming ability of fish, which accounts for 41.9% and 26.9%, respectively.

Interactive effects of total dissolved gas supersaturation and suspended sediment on the swimming abilities of two fish species

AbstractDischarged floods containing a large amount of suspended sediment (SS) can lead to total dissolved gas (TDG) supersaturation downstream of dams. The swimming ability of fish may be affected by TDG supersaturation and excessive SS. However, previous studies focused only on the separate effects of TDG and SS, ignoring their combined effects. In this study, juvenile rock carp and grass carp were selected to assess the interactive effects of TDG and SS on fish swimming ability. A totally crossed two‐factorial design (six TDG levels: 100%, 115%, 120%, 125%, 130% and 135%; four SS concentrations: 0, 50, 100 and 150 mg/L) was set, and the critical swimming speed (Ucrit) and the burst swimming speed (Uburst) were measured. The findings indicated that the swimming abilities (Ucrit and Uburst) of both fish species decreased with increasing TDG levels and SS concentrations. Separate exposure to TDG significantly decreased the swimming abilities of the two fish species, whereas separate exposure to SS decreased only the swimming abilities of juvenile grass carp. Juvenile rock carp exhibited weaker swimming abilities than juvenile grass carp in TDG‐supersaturated water. Additionally, the interaction between TDG and SS reduced the swimming abilities of juvenile rock carp and grass carp compared with a separate effect, but this reduction was significant only for the Ucrit of juvenile grass carp. This study demonstrates that TDG‐supersaturated water containing SS during flooding may result in fish failure through fishways.

Using fish swimming ability to refine criteria for fishway construction in Myanmar

The construction of dams and other river infrastructures is threatening migratory fish stocks in many parts of the world by greatly reducing river-floodplain connectivity. Fishways are technical tools that can restore river connectivity for migratory fishes, but their effectiveness is often limited by a lack of biological information on their target species, especially in developing countries of South East Asia. We sought to inform the design of a vertical-slot fishway for Myanmar migratory fishes, by using a flume-based vertical-slot fishway to determine if (1) their passage ability is influenced by hydraulic conditions (such as depth and head differential or ‘headloss’ between cells); and (2) fish size influences passage ability for each species. This was achieved by comparing passage success under headloss options of 50-mm and 100-mm, and by assessing the relationship between size and ability to pass the flume – in four representative migratory species: Pangasius pangasius (pangas catfish), Notopterus notopterus (featherback fish), Puntius chola (swamp barbs) and Esomus danrica (flying barbs). Our results indicated that flume passage ability was greater under the 50-mm headloss for Pangasius pangasius, Notopterus notopterus and Puntius chola; and that flume passage ability increased in larger individuals for Pangasius pangasius and Notopterus notopterus. In comparison, Esomus danrica could not ascend under either the 50-mm or 100-mm headloss options. The inter-specific variability in these results empirically demonstrates the importance of obtaining baseline biological information on the target species for planned fishways in order to optimise their effectiveness.

Swimming ability of cyprinid species (subfamily schizothoracinae) at high altitude.

The primary objective of this investigation was to study the effect of altitude on fish swimming ability. Different species were tested to ensure that the differences observed are not associated with a single species. Fish critical swimming speed and burst speed were determined using stepped-velocity tests in a Brett-type swimming respirometer. Based on the effects of water temperature and dissolved oxygen, it is clear that the swimming ability of fish decreases as altitude increases. Further, because the effects of high altitude on fish physiology go beyond the effects of lower temperature and dissolved oxygen, we recommend that fish swimming ability be tested at an altitude similar to the target fishway site to ensure the validity of fish data used for fishway design.

Collaboration between fish passage scientists and engineers: Insights from an international questionnaire

Fish passage science and practice seeks to facilitate the movement of fish around obstacles in their habitat, primarily through the construction of fishways and culverts. Successful implementation of fish passage requires collaboration between groups with very different backgrounds and expertise, including knowledge-producers (scientists who study fish passage and related topics such as fish swimming ability) and knowledge users (engineers who apply that knowledge to design fish passage solutions). To investigate the nature of collaboration between these groups, we surveyed fish passage scientists and engineers from around the world. Respondents were asked about the importance of collaboration, mechanisms of collaboration, potential barriers to collaboration, and how collaboration can be improved. Both fish passage scientists and engineers reported high importance of collaboration and that they collaborated frequently with the other group. Respondents reported that consultation with other professionals (of their discipline and the other) was the most important means of obtaining and sharing information related to fish passage science and engineering. Both groups also tended to over-estimate their knowledge and use of the other's discipline. While respondents reported high engagement in collaboration, key themes emerged with respect to barriers to collaboration and means of improving collaboration. These included lacking a shared understanding of both disciplines, professional differences, insufficient institutional support, and inadequate sharing of knowledge (e.g., reporting and publishing). Opportunities for improving collaboration identified by respondents included 1) more interdisciplinary opportunities that facilitate interaction (particularly conferences and workshops); 2) promoting collaborative projects and interactions between fish passage scientists and engineers on project teams; and 3) ensuring that information is shared between groups (e.g., through accessible publications). Findings from this research have the potential to enhance collaboration between scientists and engineers, to the benefit of fish passage and fish populations.

Determining the position of a fish passage facility entrance based on endemic fish swimming abilities and flow field.

Hydropower development can significantly mitigate climate change and reduce carbon emissions, but it can also have substantial negative impacts on river environments and fish biodiversity. Fish passage facilities are built to ensure sustainable hydropower development and the biodiversity of fish populations. The locations of the entrances to these facilities play a key role in their efficiency. This study presents a reliable approach that combines the swimming ability of fish and a numerical flow field simulation to determine the optimal location for a fish passage facility entrance. In this study, we used the Gujun Reservoir upstream of the Yangtze River as a case study. A field experiment was conducted, and the swimming abilities of eight endemic fish species in the upstream region of the Yangtze River were measured. Among the tested species, the fastest induced swimming speed (0.14m/s) was achieved by Glyptothorax sinense, while the slowest critical swimming speed (0.30m/s) was observed for Paracobitis potanini. We propose that the velocity near the fish passage facility entrance should be higher than the maximum induced swimming speed and lower than the minimum critical swimming speed, making the suitable range between 0.14 and 0.30m/s. On this basis, velocity fields 500m downstream of the dam of the Gujun Reservoir under 4 operating conditions with discharge flows of 5.7 m3/s, 23.3 m3/s, 32.5 m3/s, and 41.1 m3/s were calculated. The results showed that the flow field variation downstream of the dam was between 0.1 and 0.9m/s. After comparing the suitable areas for the target species, the left bank at location 2 was recommended as the optimal location for the fish passage facility entrance in the Gujun Reservoir.

Wild fish beat the heat

Wild animals can adapt to a wide range of temperatures. The ability to perform well in a constantly changing environment is called physiological plasticity. Physiological plasticity allows ectothermic animals, such as fishes, to maintain their metabolism even when the water that the fish is in heats up or cools down wildly. Fishes living in laboratories are less likely to have experienced temperature changes, so will their metabolism still perform well if there is a big temperature shift in their tank? Or have they lost their physiological plasticity because they have only experienced steady temperatures for more than 150 generations? Can living in steady environments affect a fish's behavior, metabolism or gene expression compared with living in a more turbulent environment? To study these questions, Rachael Morgan and colleagues from the Norwegian University of Science and Technology and the University of Greenwich, UK, compared the physiological plasticity of two populations of zebrafish: a wild population collected from India and a population raised in the lab. They aimed to understand whether living in a stable environment can change a fish's ability to perform when there is a big change in temperature.The researchers collected 300 zebrafish from the two populations and exposed each group to a variety of temperatures (from 10 to 38°C) for 1 month. They then measured the fish's swimming ability, escape response, growth rate, metabolic rate and gene expression and compared the measurements of the two groups to learn whether the lab-raised group had more difficulty in adapting to large temperature shifts than the wild group because they have less physiological plasticity.Sure enough, the lab-raised fish were less able to adjust to temperature change than the fish that had come from India. The lab-raised zebrafish were slower swimmers than wild zebrafish at all temperatures, and when escaping, lab-raised zebrafish responded more slowly than wild zebrafish, especially when in colder temperatures. In addition, the lab-raised zebrafish grew faster than the wild zebrafish, likely because domesticated animals are selected for faster growth rates. When comparing metabolism between the groups, the researchers measured the range of temperatures at which the fish could reach their maximum metabolic rates. They found that lab-raised fish could only reach their maximum metabolic rate in water temperatures between 26 and 36°C, but wild fish could reach their maximum metabolic rate over a much broader temperature range (21–38°C). Gene expression was also different among the two groups. The lab fish had greater levels of proteins that deal with stress compared with the wild fish. Interestingly, very cold temperatures were especially difficult for both groups, which may suggest that physiological plasticity is limited at these extreme temperatures.This study tells us that lab domestication affects the ability of animals to adjust to changes in their environment across several biological levels, from behaviour to gene expression. With this knowledge, scientists should take into account that domestication can change animals’ responses to an experiment when choosing study animals. Morgan and colleagues also suggest that there may be a trade-off between high levels of physiological plasticity and growth rates and warn that domestication can quickly lead to a loss of physiological plasticity.

鄱阳湖水利枢纽工程建设对草鱼江湖洄游潜在的影响

鄱阳湖是长江四大家鱼索饵、育肥的重要场所, 近年来鄱阳湖出现了枯水季水位严重降低、枯水期延长、湿地面积缩小的现象。为解决鄱阳湖水资源、水文、水生态等问题, 建议在鄱阳湖入江水道兴建控制闸水利枢纽。然而, 拟建的水利枢纽工程将打破鄱阳湖与长江的天然连通性, 可能会对四大鱼类洄游过程产生影响。通过构建二维和三维水动力模型, 分析鄱阳湖水利枢纽建设后入江水道与枢纽洄游通道的水动力学特征, 结合实验和文献获得的草鱼幼鱼和成鱼游泳能力参数, 阐明了枢纽建设对草鱼洄游的影响。结果表明: 在设计调度模式下, 草鱼幼鱼入湖期间, 湖口段适宜通过天数达到83.74%以上, 说明湖口及入江水道的水动力条件对洄游的影响较小, 同时, 枢纽工程处在过鱼高峰期仍能保持较高的过闸效率; 草鱼成鱼出湖期间, 丰、平水年闸前水动力条件对洄游的影响较小, 仅在枯水年闸前流速几乎静止, 草鱼适宜出湖天数偏低。在该调度模式下, 水利枢纽建设运行后鄱阳湖整体水动力条件能够满足草鱼洄游需求。目前设计的鱼道在高、低水位时期均出现局部流速过大的现象, 不满足过鱼条件。从四大家鱼江湖洄游的角度为鄱阳湖水利枢纽工程设计和运行提供科学参考。;Poyang Lake serves as the main feeding and fattening venue for the four major Chinese carps. In recent years, Poyang Lake has experienced a severe drop in water level during the dry season, prolonged dry season, and reduced wetland area. To tackle the problem of water resources, hydrology and water ecology in Poyang Lake, it is suggested to build a hydro-junction project which is proposed to be located at the channel connecting the Poyang Lake and the Yangtze River. Yet the to-be-built Poyang Lake Hydro-junction Project would impede the natural connection between Poyang Lake and the Yangtze River. The migration passage of the four major Chinese carps may be affected. To study the potential impact of the prospective hydro-junction project on the migration of grass carp, analysis was conducted on the hydrodynamic characteristics of the migration channel after the construction of Poyang Lake Hydro-junction Project using two-dimensional and three-dimensional hydraulic models. The swimming ability of grass carp was determined through experiment and literature review. According to the study results, more than 83.74% of the days suitable for fish passage at the entrance to the lake. The hydrodynamic conditions at the entrance and the channel into the Yangtze River had an insignificant impact on the fish migration at the time when the juvenile grass carps entered the lake. Meanwhile, the gate chamber of hydro-junction project could still maintain a high passing efficiency during the peak period of fish migration. While under the designed scheduling mode, the hydrodynamic conditions in front of the hydraulic construction had little effect on fish migration in the years of wet and normal, but the days that were favorable for the fish departure from the lake decreased in dry years caused by almost static velocity in front of the hydraulic construction when the adult grass carps left the lake. The overall hydrodynamic conditions of Poyang Lake could meet the needs of the grass carp migration during the operation period of the Poyang Lake Hydro-junction Project. However, the current design of the fishway of the Poyang Lake Hydro-junction Project suffered the excessive flow velocity in some parts during high and low water level period, which dissatisfied the required passage conditions based on fish swimming ability under the existing scheduling mode. This study was expected to provide a scientific reference for the design and operation of the Poyang Lake Hydro-junction Project from the perspective of river-lake migration of the four major Chinese carps.

КОНСТРУИРОВАНИЕ И РАСЧЕТ ТРАКТОВ ПРИГИДРОУЗЛОВЫХ РЫБОХОДНО-НЕРЕСТОВЫХ КАНАЛОВ

Purpose: development of recommendations for design and calculation procedure of the flow rate and geometric parameters of fish pass and spawning channels arranged at large river waterwork facilities. Materials and methods. The factual base for the proposed developments were survey materials for the existing Nikolaevsky and Konstantinovsky fish pass and spawning channels and design materials for the Bagaevsky fish pass and spawning channel under construction on the river Don. The development methodology was based on scientific methods of analysis and synthesis of information and technologies for the search design of fish breeding facilities. Results. The survey data of the operating fish pass and spawning canals at waterworks and the analysis of their design solutions made it possible to establish approaches to determining and the ranges of flow rate and geometric parameters, cross-sectional shapes of their tracts and fish recreation areas, as well as approaches to the choice of their layout and design solutions. Taking into account on the basis of the initial information, a general methodology for designing (substantiations, calculations and construction) fish pass and spawning canals and a method for their hydraulic calculation are proposed. When developing general and particular recommendations, known data on the biological features of anadromous-migratory behavior and the fish swimming ability were taken into account. The proposed developments are adapted to the conditions of the proposed layout and design solution of the Kochetovsky fish pass and spawning canal on the river Don. Conclusion. The survey materials of the existing fish pass and spawning canals, arranged at the Nikolaevsky and Konstantinovsky waterworks, as well as the results of the analysis of the design solution of the canal as part of the Bagaevsky waterworks under construction on the river Don. A methodological approach to the development of constructive solutions and methods for calculating the geometric parameters of the fish pass and-spawning channels tracts is proposed.

Comprehensive analysis and application of Chinese Cyprinidae swimming ability

该研究利用学术论文数据库筛选出中国鲤科鱼类游泳能力相关论文115篇，并用Origin软件进行了数据统计分析，旨在归纳和分析中国鲤科鱼类游泳能力并建立估算方法，可为正处于规划阶段和可行性研究阶段的过鱼设施流速设计提供依据.结果表明：（1）鱼类游泳速度与鱼体长度具有显著的非线性相关关系，据此建立了一系列幂函数经验公式，可为游泳能力和过鱼设施研究及设计提供依据.（2）依据所得到的经验公式和协方差分析可知，喜流水型鲤科鱼类的游泳能力>广适型>喜静水型.根据该研究得到的经验公式并结合行业规范和文献资料，对正处于规划阶段和可行性研究阶段过鱼设施流速设计的建议如下：西南地区以裂腹鱼成鱼为主要过鱼对象的过鱼设施进鱼口吸引流速范围为0.61~0.76 m/s，通道内最高流速阈值为1.28 m/s；长江中下游以四大家鱼成鱼为主要过鱼对象的进鱼口吸引流速范围为0.76~0.93 m/s，通道内最高流速阈值为1.49 m/s，以四大家鱼幼鱼为主要过鱼对象的进鱼口吸引流速范围为0.42~0.62 m/s，通道内最高流速阈值可为0.82 m/s.;In order to provide an estimation method and basis for the fish swimming ability and for the flow velocity design of fish passing facilities in the planning stage and feasibility stage, by searching the papers related to the swimming ability of Chinese Cyprinidae from the internationally recognized academic paper network database, we selected 115 and then compared them with the critical swimming speed, burst speed and total length as describing indexes by using software Origin 9.0. Results indicated:(1) The relationship between fish swimming speed and fish length is allometric rather than isometric. It is recommended that the power function can be used to fit the correlation between fish swimming speed and total length. (2) Based on the empirical formula and the covariance analysis, swimming ability of rheophilic Cyprinidae > swimming ability of semi-rheophilic Cyprinidae > swimming ability of limnophilic Cyprinidae. According to the Design code for fish passage facilities in hydropower projects in China, Guideline for fishway in water conservancy in China and literature references about fish passage facility design, as well as the empirical formula in this study, the flows for fish passing facilities in the planning and feasibility stages in southwest China and the middle and lower reaches of the Yangtze River were recommended as follows. In the southwest China, the attraction flow velocity range of the fish passing facility entrance with adult Schizothoracinae fishes as the target species is 0.61-0.76 m/s, and the maximum velocity of the passage and pool is 1.28 m/s. In the middle and lower reaches of the Yangtze River, the attraction flow velocity range of the fish passing facility entrance with adult four major Chinese carps as the target species is 0.76-0.93 m/s, and the maximum velocity of the passage and pool is 1.49 m/s. The attraction flow velocity range of the fish passing facility entrance with juvenile four major Chinese carps as the target species is 0.42-0.62 m/s, and the maximum velocity of the passage and pool is 0.82 m/s.

Effects of continuous exposure to total dissolved gas supersaturation on swimming ability and recovery in grass carp (Ctenopharyngodon idella)

AbstractTotal dissolved gas (TDG) supersaturation caused by flood discharge water is becoming a serious environmental problem that threatens the survival of fish. The swimming ability of fish may be influenced by TDG supersaturation. To investigate the effects of continuous exposure to TDG supersaturation on fish swimming ability, we measured the critical swimming speed (Ucrit) and burst swimming speed (Uburst) of grass carp continuously exposed to TDG supersaturation. The Ucrit values of grass carp were 6.34–3.68 body length per second (BL/s) at 100%, 105%, 110%, 115%, 120%, 125%, 130% and 135% TDG, while the Uburst values were 10.2–8.96 BL/s at these TDG levels. The swimming ability (Ucrit and Uburst) of grass carp decreased with increasing TDG levels and was significantly decreased at higher TDG levels (>120%). A swimming ability recovery test was used to investigate the effects of recovery on the swimming ability of grass carp continuously exposed to TDG supersaturation. When grass carp experienced exposures of 115%, 120%, 125%, 130% and 135% TDG, the recovery ratios of Ucrit were 76%–82% and 77%–86% after recovering for 1 and 2 h, respectively, in freshwater (100% TDG). The recovery ratios of Uburst of grass carp were 84%–98% and 95%–97% under the same recovery conditions and TDG levels. The results showed that the recovery ratios of both Ucrit and Uburst increased with the extension of the recovery time. The swimming ability of grass carp provided with a 2‐h recovery time recovered almost completely.

Effect of torsional spring and shape on the performance of bioinspired caudal fin

The swimming ability of fish is greatly influenced by the hydrodynamics of their caudal fins. In this paper, the effects of flexibility and shape on the performance of a bioinspired panel are numerically studied. The flexibility is simplified as a torsional spring, and three typical shapes (i.e., square, convex, and concave shapes) are considered. The results are obtained based on three-dimensional numerical simulations of flapping panels at Re = 1000 and St = 0.5. It is shown that the flexibility can significantly affect the performance of pitching panels, by changing the phase lag between the motions of the fore and hind parts. When the phase lag is in the range of 0.1π–0.6π, the performance improvement can be obtained by the flexible panels, as compared with the rigid panel. Moreover, the maximum thrust (or efficiency) can be achieved by a flexible panel when the phase lag is approximately 0.35π (or 0.24π). On the other hand, it is found that the convex shape is optimal for thrust generation, but the square shape is optimal for propulsive efficiency. Moreover, the mechanism by which flexibility and shape can influence the performance of the pitching panel is analyzed. The results obtained here may provide some light on designing the efficient propulsor for microunderwater robots.

Optimization of fishway attraction flow based on endemic fish swimming performance and hydraulics

Attracting fish to fishway entrances is vital for ensuring successful and timely passage at dams and other in-stream barriers. This requires knowledge of both the target species' swimming ability and the hydrodynamics near the entrance. However, such knowledge is not always available during the initial design phase. The objective of this study is to propose suitable hydraulic conditions for the entrance of a fish passage facility to be built on the Jing River in China. We measured the swimming ability of three endemic cyprinid species (Phoxinus lagowskii, Triplophysa stoliczkae and Opsariich thysbidens) using three metrics: 1) induced flow velocity, 2) critical swimming speed, and 3) burst swimming speed. We then used a reduced-scale physical model of the fish passage facility and a verified 3D numerical hydrodynamic model to simulate the flow field under three fish collecting channel (FCC) operation scenarios. Connecting the fish swimming ability and the flow conditions in the river allowed to define the migration corridors present downstream of the FCC entrance under the different operation scenarios. Although the local velocity in the river near the fish passage entrance never exceeded the burst swimming speed of the target species, large backflow areas developed below the entrance in scenarios 1 and 2. The addition of a spur dike downstream of the entrance decreased the development of backflows, optimizing the width of the migration corridor by nearly 32%. This research presents a reliable and quantitative approach that combines fish swimming ability metrics and hydraulic characterization for optimizing attraction flows at fishway entrances.

A Method for Estimating the Velocity at Which Anaerobic Metabolism Begins in Swimming Fish

Anaerobic metabolism begins before fish reach their critical swimming speed. Anaerobic metabolism affects the swimming ability of fish, which is not conducive to their upward tracking. The initiation of anaerobic metabolism therefore provides a better predictor of flow barriers than critical swimming speed. To estimate the anaerobic element of metabolism for swimming fish, the respiratory metabolism and swimming performance of adult crucian carp (Carassius auratus, mass = 260.10 ± 7.93, body length = 19.32 ± 0.24) were tested in a closed tank at 20 ± 1 °C. The swimming behavior and rate of oxygen consumption of these carp were recorded at various swimming speeds. Results indicate (1) The critical swimming speed of the crucian carp was 0.85 ± 0.032 m/s (4.40 ± 0.16 BL/s). (2) When a power function was fitted to the data, oxygen consumption, as a function of swimming speed, was determined to be AMR = 131.24 + 461.26Us1.27 (R2 = 0.948, p < 0.001) and the power value (1.27) of Us indicated high swimming efficiency. (3) Increased swimming speed led to increases in the tail beat frequency. (4) Swimming costs were calculated via rate of oxygen consumption and hydrodynamic modeling. Then, the drag coefficient of the crucian carp during swimming was calibrated (0.126–0.140), and the velocity at which anaerobic metabolism was initiated was estimated (0.52 m/s), via the new method described herein. This study adds to our understanding of the metabolic patterns of fish at different swimming speeds.

Coupled influence of flow velocity and water temperature on grass carp swimming behaviour and gonad development

AbstractReproductive migration is an essential phase in the life of many fish. During this process, swimming behaviour and gonad development are key factors related to the migration quality, and both factors are strongly influenced by water temperature and flow velocity. Many studies have explored the separate effects of these variables on fish swimming ability or gonad development, but researchers have seldom investigated the simultaneous effects of low flow velocity and water temperature on the fish swimming behaviour and gonad development. To provide that knowledge, we conducted laboratory experiments that explored the coupled effects of low water temperature and flow on warm water fish swimming behaviour and gonad development. At five temperatures (16, 18, 20, 22, and 24°C), we observed the movement of migratory warmwater grass carp (Ctenopharyngodon idellus) at seven flow velocities (0.15, 0.2, 0.25, 0.3, 0.35, 0.40, and 0.45 m/s), then explored their gonad development by comparing the level of plasma 17β‐estradiol and testosterone in fish travelling through a simulated fish way (flow stimulation) and in a fish tank (no flow stimulation). We used Bayesian networks to explore the acceptable hydrological condition for fish migration. We found that the minimum flow velocity for acceptable migration quality is a function of the water temperature, and that increasing water temperature improves fish movement success and increases the movement distance, especially at a low flow velocity. In addition, increasing water temperature (between 16 and 24°C in this experiment design) can enhance the effect of flow stimulation on gonad development. Overall, our results can broaden the understanding of reducing water temperature and flow velocity in fish swimming behaviour and gonad development, provide basic data to support hydrological process controls and the development of measures to protect fish migration.

Tunabot Flex: a tuna-inspired robot with body flexibility improves high-performance swimming

Tunas are flexible, high-performance open ocean swimmers that operate at high frequencies to achieve high swimming speeds. Most fish-like robotic systems operate at low frequencies (≤3 Hz) resulting in low swim speeds (≤1.5 body lengths per second), and the cost of transport (COT) is often one to four orders of magnitude higher than that of tunas. Furthermore, the impact of body flexibility on high-performance fish swimming remains unknown. Here we design and test a research platform based on yellowfin tuna (Thunnus albacares) to investigate the role of body flexibility and to close the performance gap between robotic and biological systems. This single-motor platform, termed Tunabot Flex, measures 25.5 cm in length. Flexibility is varied through joints in the tail to produce three tested configurations. We find that increasing body flexibility improves self-propelled swimming speeds on average by 0.5 body lengths per second while reducing the minimum COT by 53%. The most flexible configuration swims 4.60 body lengths per second with a tail beat frequency of 8.0 Hz and a COT measuring 18.4 J kg−1 m−1. We then compare these results in addition to the midline kinematics, stride length, and Strouhal number with yellowfin tuna data. The COT of Tunabot Flex’s most flexible configuration is less than a half-order of magnitude greater than that of yellowfin tuna across all tested speeds. Tunabot Flex provides a new baseline for the development of future bio-inspired underwater vehicles that aim to explore a fish-like, high-performance space and close the gap between engineered robotic systems and fish swimming ability.

Effects of obstacles and flow velocity on locomotory behavior in juvenile, silver carp, Hypophthalmichthys molitrix

AbstractWe currently have only a minimal understanding of energy‐saving strategies of fish in unsteady flows. In this study, we found that obstacle shape can affect swimming ability of fish: our results suggested that a half cylinder improved critical swimming speed of silver carp (Hypophthalmichthys molitrix) compared with swimming downstream of a full cylinder, square tube or for free‐flow conditions. We also discovered how silver carp alter their locomotory behavior in response to turbulent flow caused by varying flow velocities around obstacles. At a flow velocity of 1 BL/s (body length per second), the fish spent similar percentages of time between holding station and moving forward behind the half cylinder: their motions resembled freestream swimming behavior. The greatest percentage of time spent downstream of the half cylinder occurred at a flow velocity of 5 BL/s. Fish were unstable and displayed irregular body motions with large lateral displacement at 5 BL/s. However, the fish held station for a long time and moved forward steadily behind the half cylinder at 3 BL/s. In holding station behind the half cylinder, fish maintained constant tail‐beat frequency and tail‐ beat amplitude when flow velocity was increased from 1 to 3 BL/s. In moving forward behind the half cylinder, fish increased tail‐beat frequency and tail‐beat amplitude while maintaining constant ground swimming speed, swimming acceleration and ground stride when flow velocity was increased from 3 to 5 BL/s. Moreover, fish positioned their snouts in a small area approximately 1–3 BL downstream from the half cylinder at 3 BL/s. These behaviors support the hypothesis that turbulence behind a half cylinder was a suitable location for fish to conserve energy at 3 BL/s. Our results indicate that the combined effect of obstacles and flow velocity influence fish locomotory behavior, and some combinations may be beneficial to fish energy expenditure swimming in unsteady flow.

The Effect of Acute Erythromycin Exposure on the Swimming Ability of Zebrafish (Danio rerio) and Medaka (Oryzias latipes).

Erythromycin is a widely used antibiotic, and erythromycin contamination may pose a threat to aquatic organisms. However, little is known about the adverse effects of erythromycin on swimming ability. To quantify erythromycin-induced damage to fish swimming ability, Oryzias latipes and Danio rerio were acutely exposed to erythromycin. The swimming ability of the experimental fish was measured after exposure to varying doses of erythromycin (2 µg/L, 20 µg/L, 200 µg/L, and 2 mg/L) for 96 h. Burst speed (Uburst) and critical swimming speed (Ucrit) of experimental fish significantly decreased. In addition, gene expression analysis of O. latipes and D. rerio under erythromycin treatment (2 mg/L) showed that the expression of genes related to energy metabolism in the muscle was significantly reduced in both species of fish. However, the gene expression pattern in the head of the two species was differentially impacted; D. rerio showed endocrine disruption, while phototransduction was impacted in O. latipes. The results of our study may be used as a reference to control erythromycin pollution in natural rivers.

Relationship between swimming capacities and morphological traits of fish larvae at settlement stage: a study of several coastal Mediterranean species.

Experimental measurements were made in the laboratory to determine the swimming capacities of settlement-stage fish larvae of several Mediterranean coastal species collected from the nearshore waters of Corsica, France. Critical swimming speed (Ucrit , cm s-1 ) was measured to provide a realistic laboratory estimate of in situ swimming speed. Morphometric traits were measured to assess potential predictors of a species' swimming ability and, when possible, daily otolith increments were used to estimate age. Observed swimming speeds were consistent with other temperate species and demonstrated that the tested species are competent swimmers and not passive components of their environment. Morphological traits varied in their correlation with Ucrit across groups and species. Direct measurements of morphological traits were better predictors than calculated ratios. Pelagic larval duration had little relationship with swimming speed among species for which daily otolith increments were counted. In addition to expanding the database on swimming capacities of settlement-stage fish larvae in the Mediterranean Sea, this study also developed methods that simplify the assessment of larval fish swimming ability. Swimming speed data are essential for improving larval dispersal models and for predicting recruitment rates in coastal fish populations.