Automatically Detect and Track Multiple Fish Swimming in Shallow Water with Frequent Occlusion

Due to its universality, swarm behavior in nature attracts much attention of scientists from many fields. Fish schools are examples of biological communities that demonstrate swarm behavior. The detection and tracking of fish in a school are of important significance for the quantitative research on swarm behavior. However, different from other biological communities, there are three problems in the detection and tracking of fish school, that is, variable appearances, complex motion and frequent occlusion. To solve these problems, we propose an effective method of fish detection and tracking. In this method, first, the fish head region is positioned through extremum detection and ellipse fitting; second, The Kalman filtering and feature matching are used to track the target in complex motion; finally, according to the feature information obtained by the detection and tracking, the tracking problems caused by frequent occlusion are processed through trajectory linking. We apply this method to track swimming fish school of different densities. The experimental results show that the proposed method is both accurate and reliable.     

Automatic Realistic Real Time Stimulation/Recording in Weakly Electric Fish: Long Time Behavior Characterization in Freely Swimming Fish and Stimuli Discrimination

Weakly electric fish are unique model systems in neuroethology, that allow experimentalists to non-invasively, access, central nervous system generated spatio-temporal electric patterns of pulses with roles in at least 2 complex and incompletely understood abilities: electrocommunication and electrolocation. Pulse-type electric fish alter their inter pulse intervals (IPIs) according to different behavioral contexts as aggression, hiding and mating. Nevertheless, only a few behavioral studies comparing the influence of different stimuli IPIs in the fish electric response have been conducted. We developed an apparatus that allows real time automatic realistic stimulation and simultaneous recording of electric pulses in freely moving Gymnotus carapo for several days. We detected and recorded pulse timestamps independently of the fish’s position for days. A stimulus fish was mimicked by a dipole electrode that reproduced the voltage time series of real conspecific according to previously recorded timestamp sequences. We characterized fish behavior and the eletrocommunication in 2 conditions: stimulated by IPIs pre-recorded from other fish and random IPI ones. All stimuli pulses had the exact Gymontus carapo waveform. All fish presented a surprisingly long transient exploratory behavior (more than 8 h) when exposed to a new environment in the absence of electrical stimuli. Further, we also show that fish are able to discriminate between real and random stimuli distributions by changing several characteristics of their IPI distribution.     

Toward Fast and Efficient Mobility in Aquatic Environment: A Robot with Compliant Swimming Appendages Inspired by a Water Beetle

Water beetles are proficient drag-powered swimmers,with oar-like legs.Inspired by this mechamsm,here we propose a miniature robot,with mobility provided by a pair of legs with swimming appendages.The robot has optimized linkage structure to maximize the stroke angle,which is actuated by a single DC motor with a series of gears and a spring.A simplified swimming appendage model is proposed to calculate the deflection due to the applied drag force,and is compared with simulated data using COMSOL Multiphysics.Also,the swimming appendages are optimized by considering their locations on the legs using two fitness functions,and six different configurations are selected.We investigate the performance of the robot with various types of appendage using a high-speed camera,and motion capture cameras.The robot with the proposed configuration exhibits fast and efficient movement compared with other robots.In addition,the locomotion of the robot is analyzed by considering its dynamics,and compared with that of a water boatman (Corixidae).     

被动游泳运动对小鼠抑郁样行为及其肠道菌群组成的影响

被动游泳运动可诱发小鼠抑郁样行为,游泳环境的改变已成为抑郁样行为严重程度影响因素之一。观察不同水质、水温及持续时间对被动游泳小鼠抑郁样行为的影响,并初步探讨肠道菌群组成与抑郁样行为的关系。通过不同条件下的被动游泳运动建立抑郁样行为小鼠模型。采用糖水偏好实验及强迫游泳实验评价其行为学变化;采用16S rDNA高通量测序技术及实时荧光定量PCR技术对小鼠肠道菌群进行分子生态学分析。被动游泳16周后,各模型组小鼠体质量及糖水偏爱度均较正常对照组降低,而不动时间则有所延长。其中,室温海水游泳15 min小鼠体质量及糖水偏爱度降低程度最大,不动时间最长,与正常对照组比较,均具有显著性差异（P<0.05）。各模型组小鼠肠道菌群Chao指数、Shannon指数及PCoA分析均较正常对照组具有显著性差异（P<0.05）,其从门水平到属水平的丰度也发生不同程度改变。其中,室温海水游泳15 min小鼠肠道菌群组成变化程度最大,并发生拟杆菌属、普氏菌属等多个菌属的富集以及乳杆菌属丰度的减少,实时荧光定量PCR实验也得到了较为一致的结果（P<0.05）。以上结果表明,被动游泳运动可导致小鼠抑郁样行为的发生,其肠道菌群组成也发生明显改变;同时,菌群组成的改变会随着抑郁样行为的严重程度而有所变化。     

Differences in Swimming Ability and Behavior in Response to High Water Velocities among Native and Nonnative Fishes

We conducted swimming performance tests on native and nonnative fishes commonly found in Arizona streams to evaluate the extent of differences in swimming ability among species. Fishes with similar mean lengths were subjected to stepwise increases in water velocity in a laboratory swim tunnel until fish could no longer maintain position. Nonnative fathead minnows Pimephales promelas and red shiners Cyprinella lutrensis exhibited swimming abilities similar to native longfin dace Agosia chrysogaster, speckled dace Rhinichthys osculus and spikedace Meda fulgida. Nonnative mosquitofish Gambusia affinis exhibited swimming ability similar to native Gila topminnows Poeciliopsis occidentalis. Desert suckers Catostomus clarki, bluehead suckers Catostomus discobolus and speckled dace exhibited behavioral responses to high water velocities that may confer energetic advantages in swift water. Differences in swimming ability do not appear to adequately explain the disproportionate removal of nonnative fishes via flooding. Behavioral responses to high flows are more likely the mechanism that allows native fish to persist in streams during flood events.     

Feeding and Swimming Behavior in Grazing Microzooplankton1,2

ABSTRACT A random-walk model of food-searching behavior is considered for the microzooplankton. It is suggested that in still waters a random walk of the conventional sort, modeled by a Wiener process, is less efficient than a Levy walk (a random walk whose excursions follow a Levy distribution) with Levy parameter less than two. For Levy parameter less than one, however, little advantage is gained by further reduction. In turbulent water, on the other hand, dispersion due to a random walk is dominated by the turbulent diffusion of the medium so that the Levy parameter appears to be less important. The effect of chemosensory responses is considered. It is suggested that these are most useful in still water, whereas in turbulent water their value would be less, and a non-specific filtering behavior might be more plausible.     

Kinematic Comparison of Forward and Backward Swimming and Maneuvering in a Self-Propelled Sub-Carangiform Robotic Fish

We make a thorough kinematic comparison of forward and backward swimming and maneuvering on a self-propelled robot platform that uses sub-carangifbrm swimming as the primary propulsor. An improved Central Pattern Generator （CPG） model allowing free adjustment of phase relationship and directional bias is employed to achieve flexible swimming and smooth transition. Considering the characteristics of forward swimming in carangiform fish and backward swimming in anguilliform fish, various backward swimming patterns for the sub-carangiform robotic fish are suitably created by reversing the direction of propagating propulsive waves. Through a combined use of the CPG control and closed-loop swimming direction control strategy, flexible and precise turning maneuvers in both forward and backward swimming are implemented and compared. By contrast with forward swimming, backward swimming requires a higher frequency or an increased lateral displacement to reach the same relative swimming speed. Noticeably, the phase difference shows a greater impact on forward swimming than on backward swimming. Our observations also indicate that the robotic fish achieves a larger turning rate in forward maneuvering than in backward maneuvering, yet these two maneuvers display comparable turning precision.     

Quantifying Fish Swimming Behavior in Response to Acute Exposure of Aqueous Copper Using Computer Assisted Video and Digital Image Analysis

Behavioral responses of aquatic organisms to environmental contaminants can be precursors of other effects such as survival, growth, or reproduction. However, these responses may be subtle, and measurement can be challenging. Using juvenile white sturgeon (Acipenser transmontanus) with copper exposures, this paper illustrates techniques used for quantifying behavioral responses using computer assisted video and digital image analysis. In previous studies severe impairments in swimming behavior were observed among early life stage white sturgeon during acute and chronic exposures to copper. Sturgeon behavior was rapidly impaired and to the extent that survival in the field would be jeopardized, as fish would be swept downstream, or readily captured by predators. The objectives of this investigation were to illustrate protocols to quantify swimming activity during a series of acute copper exposures to determine time to effect during early lifestage development, and to understand the significance of these responses relative to survival of these vulnerable early lifestage fish. With mortality being on a time continuum, determining when copper first affects swimming ability helps us to understand the implications for population level effects. The techniques used are readily adaptable to experimental designs with other organisms and stressors.     

Design and Implementation of Paired Pectoral Fins Locomotion of Labriform Fish Applied to a Fish Robot

In present,there are increasing interests in the research on mechanical and control system of underwater vehicles.Theseongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations,scientific deep ocean surveys,military purposes,ecological and water environmental studies,and also entertainments.However,the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency andmaneuverability.The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrustforces which make the control of the position and motion difficult.On the other hand,fishes and other aquatic animals are efficient swimmers,posses high maneuverability,are able to followtrajectories,can efficiently stabilize themselves in currents and surges,create less wakes than currently used underwater vehicle,and also have a noiseless propulsion.The fish’s locomotion mechanism is mainly controlled by its caudal fin and paired pectoralfins.They are classified into Body and/or Caudal Fin(BCF)and Median and/or paired Pectoral Fins(MPF).The study of highlyefficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism.There are few studies on underwater vehicles or fish robots using paired pectoral fins as thruster.The work presented in thispaper represents a contribution in this area covering study,design and implementation of locomotion mechanisms of pairedpectoral fins in a fish robot.The performance and viability of the biomimetic method for underwater vehicles are highlightedthrough in-water experiment of a robotic fish.     

Dynamic Modeling and Experiment of a Fish Robot with a Flexible Tail Fin

This paper presents the dynamic modeling of a flexible tail for a robotic fish. For this purpose firstly, the flexible tail was simplified as a slewing beam actuated by a driving moment. The governing equation of the flexible tail was derived by using the Euler-Bernoulli theory. In this equation, the resistive forces were estimated as a term analogous to viscous damping. Then, the modal analysis method was applied in order to derive an analytical solution of the governing equation, by which the relationship between the driving moment and the lateral movement of the flexible tail was described. Finally, simulations and experiments were carried out and the results were compared to verify the accuracy of the dynamic model. It was proved that the dynamic model of a fish robot with a flexible tail fin well explains the real behavior of robotic fish in underwater environment.     

The Influence of Parental Color Morph on Mate Choice in the Cichlid Fish Cichlasoma nigrofasciatum

Cichlasoma nigrofasciatum of two different color morphs (striped or white), each of which had been taken care of from spawning up to 7 weeks of age by foster parents of the other color morph, were put together in a “free choice situation” and tested for their preference to spawn with a mate of the striped or of the white morph. The number of pairs of the same color (striped × striped, white × white) and of different color (“mixed” pairs, striped × white) was recorded and compared with the results of control fish. The latter had been taken care of from spawning up to 7 weeks of age by foster parents of the same color morph and were also tested in a free choice situation. The influence of parental color morph on mate choice was analysed in the first mate choice of naive animals (breeding for the first time). The stability over time of the preferences observed in the naive animals was then studied in the 18 months following the first mate choice experiment. Our results show that if young Cichlasoma nigrofasciatum had been taken care of by foster parents of the other color morph, but had grown up with siblings of their own color morph, approximately 9 % of the matings involved partners which had a different color (mixed pairs). In contrast, young which had been taken care of by foster parents of their own color morph and had grown up with siblings of their own color were completely segregated according to color during breeding (striped pairs or white pairs) and never formed mixed pairs. The importance of the influence of parental and sibling color morph on the preference to mate with a particular morph and, consequently, on speciation in cichlids in general are discussed.     

Towards Physarum Robots： Computing and Manipulating on Water Surface

Plasmodium of Physarum polycephalum is an ideal biological substrate for implementing concurrent and parallel com-putation, including combinatorial geometry and optimization on graphs. The scoping experiments on Physarum computing in conditions of minimal friction, on the water surface were performed. The laboratory and computer experimental results show that plasmodium of Physarum is capable of computing a basic spanning tree and manipulating of light-weight objects. We speculate that our results pave the pathways towards the design and implementation of amorphous biological robots.     

Syndromes or Flexibility: Behavior during a Life History Transition of a Coral Reef Fish

The theory of behavioral syndromes focuses on quantifying variation in behavior within and among individual organisms and attempts to account for the maintenance of differences in behavior that occur in a consistent manner among individuals. Behavioral syndromes have potentially important ecological consequences (e.g. survivorship tradeoffs) and can be shaped by population dynamics through selective mortality. Here, we search for any evidence for consistency of behavior across situations in juveniles of a common damselfish, Pomacentrus amboinensis (Pomacentridae) at the transition between larval habitats in the plankton and juvenile habitats on the reef. Naïve fish leaving the pelagic phase to settle on reefs were caught by light traps and their behaviors observed using similar methods across three different situations (small aquaria, large aquaria, field setting); all of which represent low risk and well-sheltered environments. Seven behavioral traits were compared within and among individuals across situations to determine if consistent behavioral syndromes existed. No consistency was found in any single or combination of behavioral traits for individuals across all situations. We suggest that high behavioral flexibility is likely beneficial for newly-settled fish at this ontogenetic transition and it is possible that consistent behavioral syndromes are unlikely to emerge in juveniles until environmental experience is gained or certain combinations of behaviors are favored by selective mortality.     

Towards Physarum Robots: Computing and Manipulating on Water Surface

Plasmodium of Physarum polycephalum is an ideal biological substrate for implementing concurrent anu parauel computation, including combinatorial geometry and optimization on graphs. The scoping experiments on Physarum computing in conditions of minimal friction, on the water surface were performed. The laboratory and computer experimental results show that plasmodium of Physarum is capable of computing a basic spanning tree and manipulating of light-weight objects. We speculate that our results pave the pathways towards the design and implementation of amorphous biological robots.