Lateralized Kinematics of Predation Behavior in a Lake Tanganyika Scale-Eating Cichlid Fish

Behavioral lateralization has been documented in many vertebrates. The scale-eating cichlid fish Perissodus microlepis is well known for exhibiting lateral dimorphism in its mouth morphology and lateralized behavior in robbing scales from prey fish. A previous field study indicated that this mouth asymmetry closely correlates with the side on which prey is attacked, but details of this species' predation behavior have not been previously analyzed because of the rapidity of the movements. Here, we studied scale-eating behavior in cichlids in a tank through high-speed video monitoring and quantitative assessment of behavioral laterality and kinematics. The fish observed showed a clear bias toward striking on one side, which closely correlated with their asymmetric mouth morphologies. Furthermore, the maximum angular velocity and amplitude of body flexion were significantly larger during attacks on the preferred side compared to those on the nonpreferred side, permitting increased predation success. In contrast, no such lateral difference in movement elements was observed in acoustically evoked flexion during the escape response, which is similar to flexion during scale eating and suggests that they share a common motor control pathway. Thus the neuronal circuits controlling body flexion during scale eating may be functionally lateralized upstream of this common motor pathway

Validation of a model to predict fish passage mortality in pumping stations

A total of 1253 live cyprinids and eel were exposed to a centrifugal pump to study fish damage rates in a wide operating range. The observed types of injuries were consistent with a mechanical cause of damage. The measured mortality rates for cyprinids show a fair agreement with a blade strike model based on empirical data by Electric Power Research Institute. Analysis of the experiments with eel led to a new correlation for the blade mortality ratio for this species; lethal injury rate is shown to be zero up to a strike velocity of 8 m·s–1 and increases linearly to 42% for a strike velocity of 15 m·s–1. Use was made of video recordings that provided valuable information on the orientation and distribution of fish approaching the impeller. Results are presented using a new method to visualize fish mortality from a pump in its entire operating range using graphs of pressure head versus flow rate. The theory of pump hydrodynamics is used to derive a method to scale results of fish damage rate, obtained either by a model or by experiments, to different pump sizes, shaft speeds, or fish lengths. This will prove essential for a valid interpretation of pump experiments with fish

Validation of a model to predict fish passage mortality in pumping stations

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Exploring the possibilities of seaward migrating juvenile European sturgeon Acipenser sturio L., in the Dutch part of the River Rhine

International audienceThe water quality of the River Rhine has improved and might again suit the critically endangered European sturgeon A. sturio L, which was extirpated from the river by 1950. This study describes the tracking of 43 juvenile hatcheryreared A. sturio, in the Dutch part of the Lower Rhine and Delta, originating from an ex situ measure of the River Gironde population. Observing in situ juvenile downstream migration could help to identify essential habitats and potential threats, before actual stocking. Fish were implanted with transponders of the NEDAP Trail® system and released in two batches, in May (n =13) and June 2012 (n =30). Détections collected (n =26) exhibited no upstream movement. Testfish moved downstream with the flow. Because the historic estuary is disconnected from the North Sea by a sea lock “Haringvlietdam”, the migration of the fish followed the redirected river discharge into the Port of Rotterdam (161 km). 96 % (n =19) of the detections was collected from the harbor in brackish water, where fish presumably acclimatized to higher salinities. 14%(n =6) of the sturgeons were recaptured in coastal waters by beam trawlers, five within 1 month after release. It is concluded that sustainable coastal fisheries is a key-condition for rehabilitation of the European sturgeon. Adapted management of the sea lock will reconnect the estuary to the North Sea and create more favorable conditions for the species in the Lower Rhine and Delta

Biological inspiration: From carangiform fish to multi-joint robotic fish

This paper presents a novel approach to modelling carangiform fish-like swimming motion for multi-joint robotic fish so that they can obtain fish-like behaviours and mimic the body motion of carangiform fish. A given body motion function of fish swimming is firstly converted to a tail motion function which describes the tail motion relative to the head. Then, the tail motion function is discretized into a series of tail postures over time. Thirdly, a digital approximation method calculates the turning angles of joints in the tail to approximate each tail posture; and finally, these angles are grouped into a look-up table, or regressed to a time-dependent function, for practically controlling the tail motors in a multi-joint robotic fish. The paper made three contributions: tail motion relative to the head, an error function for digital approximation and regressing a look-up table for online optimization. To prove the feasibility of the proposed methodology, two basic swimming motion patterns, cruise straight and C-shape sharp turning, are modelled and implemented in our robotic fish. The experimental results show that the relative tail motion and the approximation error function are good choices and the proposed method is feasible. © 2010 Jilin University