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Killer whales (Orcinus orca) feeding on herring (Clupea harengus) in a fjord in northern Norway were observed using underwater video. The whales cooperatively herded herring into tight schools close to the surface. During herding and feeding, killer whales swam around and under a school of herring, periodically lunging at it and stunning the herring by slapping them with the underside of their flukes while completely submerged. The kinematics of tail-slapping were analysed in detail. Tail-slaps were made up of a biphasic behaviour consisting of two phases with opposite angles of attack, a preparatory phase (negative angles of attack) and a slap phase (positive angles of attack). During the slap phase, the mean maximum angle of attack of the flukes was 47 degrees. The maximum speed of the flukes, measured at the notch, increased with whale length (L(w)) and was 2.2 L(w)s(−)(1), while the maximum acceleration of the flukes was size-independent and was 48 m s(−)(2). When killer whales slapped the herring successfully, disoriented herring appeared on the video at approximately the time of maximum fluke velocity, in synchrony with a loud noise. This noise was not heard when the tail-slaps ‘missed’ the target, suggesting that the herring were stunned by physical contact. Killer whales then ate the stunned herring one by one. Of the tail-slaps observed, 61 % were preceded by lunges into the school. We suggest that lunging was aimed at directing the school rather than at capturing the herring, since it occurred at a relatively low speed and there were no observations of the killer whales attempting to capture the herring during lunging behaviour. Given the high performance of the tail-slaps in terms of speed and acceleration, we suggest that tail-slapping by killer whales is a more efficient strategy of prey capture than whole-body attacks, since acceleration and manoeuvrability are likely to be poor in such large vertebrates.

The escape behaviour of solitary herring (Clupea harengus L.) startled by a sound stimulus was observed by means of high-speed video-filming. The results were compared with data from a previous study on the escape behaviour of schooling herring. Escape responses were divided into “away responses” and “towards responses” according to the orientation of the C-bend of the body relative to the stimulus. The proportion of away responses was smaller for solitary than for schooling herring. In solitary herring, the subsequent escape trajectories of fish making initial away responses showed a bimodal pattern of distribution, with modes at 130 and 180° from the stimulus. Trajectories following towards responses, however, were mainly within the semicircle directed at the stimulus, and their pattern of distribution differed from that of away responses. This result contrasts with observations on schooling herring, whose trajectories following both initial away and towards responses are directed away from the stimulus. In addition, we measured the response latency, defined as the interval of time between stimulus presentation and the first detectable movement of the fish. Solitary herring showed a higher proportion of short-latency responses (latency

Foraging and the evasion of predators are fundamental for the survival of organisms, but they impose contrasting demands that can influence performance in each behavior. Previous studies suggested that foraging organisms may experience decreased vigilance to attacks by predators; however, little is known about the effect of foraging on escape performance with respect to the kinematics and the timing of the response. This study tested the hypothesis that engaging in foraging activities affected escape performance by comparing fast-start escape responses of silver-spotted sculpins Blepsias cirrhosus under three conditions: (1) control (no foraging involved), (2) while targeting prey, and (3) immediately after capture of prey. Escape response variables (non-locomotor and locomotor) were analyzed from high-speed videos. Responsiveness was lower immediately after capturing a prey item compared with the other two treatments, and latency of performance was higher in the control treatment than in the other two. Locomotor variables such as maximum speed, maximum acceleration, and turning rates did not show statistical differences among the three groups. Our results demonstrate that foraging can negatively affect two fundamental components of the escape response: (1) responsiveness and (2) latency of escape, suggesting that engaging in foraging may decrease an individual's ability to successfully evade predators.

International audience; Teleost fishes exhibit wide and temporally stable inter-individual variation in a suite of aerobic and anaerobic locomotor traits. One mechanism that could allow such variation to persist within populations is the presence of tradeoffs between aerobic and anaerobic performance, such that individuals with a high capacity for one type of performance have a reduced capacity for the other. We investigated this possibility in European seabass Dicentrarchuslabrax, each measured for a battery of indicators of maximum locomotor performance. Aerobic traits comprised active metabolic rate, aerobic scope for activity, maximum aerobic swimming speed, and stride length, using a constant acceleration test. Anaerobic traits comprised maximum speed during an escape response, maximum sprint speed, and maximum anaerobic burst speed during constant acceleration. The data provided evidence of significant variation in performance among individuals, but there was no evidence of any trade-offs among any traits of aerobic versus anaerobic swimming performance. Furthermore, the anaerobic traits were not correlated significantly among each other, despite relying on the same muscular structures. Thus, the variation observed may reflect trade-offs with other morphological, physiological or behavioural traits.

Summary 1. Biological responses to warming are presently based on the assumption that species will remain within their bioclimatic envelope as environmental conditions change. As a result, changes in the relative abundance of several marine species have been documented over the last decades. This suggests that warming may drive novel interspecific interactions to occur (i.e. invasive vs. native species) or may intensify the strength of pre-existing ones (i.e. warm vs. cold adapted). For mobile species, habitat relocation is a viable solution to track tolerable conditions and reduce competitive costs, resulting in ‘winner’ species dominating the best quality habitat at the expense of ‘loser’ species. 2. Here, we focus on the importance of warming in exacerbating interspecific interactions between two sympatric fishes. We assessed the relocation response of the cool-water fish Coris julis (a potential ‘loser’ species in warming scenarios) at increasing relative dominance of the warm-water fish Thalassoma pavo (a ‘winner’ species). These wrasses are widespread in the Mediterranean nearshore waters. C. julis tolerates cooler waters and is found throughout the basin. T. pavo is common along southern coasts, although the species range is expanding northwards as the Mediterranean warms. 3. We surveyed habitat patterns along a thermo-latitudinal gradient in the Western Mediterranean Sea and manipulated seawater temperature under two scenarios (present day vs. projected) in outdoor arenas. Our results show that the cool-water species relocates to a lesspreferred seagrass habitat and undergoes lower behavioural performance in warmer environments, provided the relative dominance of its warm-water antagonist is high. 4. The results suggest that expected warming will act synergistically with increased relative dominance of a warm-water species to cause a cool-water fish to relocate in a less-preferred habitat within the same thermal environment. 5. Our study highlights the complexity of climate change effects and has broad implications for predictive models of responses to warming. To achieve more accurate predictions, further consideration is needed of the pervasive importance of species interactions. We believe these fundamental issues to be addressed to understand the biotic consequences of climate change.

Summary Unsteady water flows are common in nature, yet the swimming performance of fishes is typically evaluated at constant, steady speeds in the laboratory. We examined how cyclic changes in water flow velocity affect the swimming performance and energetics of a labriform swimmer, the shiner surfperch, Cymatogaster aggregata. Using intermittent-flow respirometry, we measured critical swimming speed (Ucrit), oxygen consumption rate (ṀO2) and pectoral fin use in steady flow versus unsteady flows with either low (0.5 body lengths per second; BLs-1) or high amplitude (1.0 BLs-1) velocity fluctuations, with a 5 s period. Individuals in low amplitude unsteady flow performed as well as fish in steady flow. However, swimming costs in high amplitude unsteady flow were on average 25.3 % higher than in steady flow and 14.2% higher than estimated values obtained from simulations based on the non-linear relationship between swimming speed and oxygen consumption rate in steady flow. Time-averaged pectoral fin use (fin beat frequency measured over 300 s) was similar among treatments. However, measures of instantaneous fin use (fin beat period) and body movement in high amplitude unsteady flow indicate that individuals with greater variation in the duration of their fin beats were better at holding station and consumed less oxygen than fish with low variation in fin beat period. These results suggest that the costs of swimming in unsteady flows are context dependent in labriform swimmers, and may be influenced by individual differences in the ability of fishes to adjust their fin beats to the flow environment.

Oxygen depletion, hypoxia, can be a common stressor in aquatic habitats, including aquaculture. Hypoxia limits aerobic swimming performance in fish, by limiting their aerobic metabolic scope. Hypoxia also elicits changes in spontaneous swimming activity, typically causing a decrease in swimming speed in sedentary species and an increase in active species. However, fish do have the capacity to avoid hypoxia and actively choose well-oxygenated areas. Hypoxia causes differences in fish behaviour in schools, it may reduce school density and size and influence activities such as shuffling within schools. Hypoxia also influences predator–prey interactions, in particular by reducing fast-start performance. Thus, through effects on swimming, hypoxia can have profound effects on species distributions in the field. In aquaculture, effects of hypoxia may be particularly significant in sea cages. It is therefore important to understand the nature and thresholds of effects of hypoxia on swimming activity to extrapolate to potential impacts on fish in aquaculture.

Ventilation frequency (F(V) ) in motionless common sole Solea solea was measured before and after a startling stimulus in normoxia and in hypoxia (15% air saturation). Startling reduced F(V) in normoxia (from mean ±s.e. 41 ± 3·3 beats min⁻¹ to near zero, i.e. 2·0 ± 1·8 beats min⁻¹) and in hypoxia (from mean ±s.e. 80 ± 4·4 to 58·8 ± 12·9 beats min⁻¹). It is suggested that the maintenance of high F(V) in hypoxia may increase the probability of detection by predators compared to normoxia.

Ecophysiology studies, performed in laboratory under controlled conditions, provide an essential tool for quantifying the impact of environmental changes on the metabolism and behaviour of individual fish. One way of quantifying such impact is by measuring the Metabolic Scope (MS) of a fish and how it is affected by environmental factors. Laboratory experiments were performed to calculate the empirical mathematical equations describing the variation of the MS of flathead grey mullet, Mugil cephalus, under different environmental conditions (water temperature and water oxygen concentration). The equation obtained was introduced into a coupled hydrodynamic-ecological numerical model able to reproduce the variability of the water temperature, salinity, dissolved oxygen, and of the main dissolved nutrients and chlorophylla. The coupled empirical-numerical model was used to reproduce the temporal and spatial variation in MS of a M. cephalus fish population in the Oristano gulf and the Cabras lagoon system (Italy), a typical Mediterranean shallow water environment. Results from numerical simulations show that during the spring and the beginning of summer period, Cabras lagoon provides a higher MS for M. cephalus than the Oristano gulf. During the rest of the year, apart from some transitional phases, the gulf provides more suitable conditions (higher MS) for M. cephalus. The obtained results are in general accordance with fisheries data, showing that M. cephalus catches are highest during the endJuly to August period, as they migrate out of the lagoon. This approach, combined with observation on the temporal and spatial distribution of fishes, can allow predictions of fish productivity in nonlimiting conditions.

The escape behaviour of schooling herring startled by an artificial sound stimulus was observed by means of high speed video filming. Response latencies showed two distinct peaks, at 30 ms and c. 100 ms. Escape responses belonging to the two latency groups showed different turning rates during the first stage of the response, and showed different escape trajectories. We suggest that long latency escapes may be responses to startled neighbours or simply weak responses to the sound stimulus. In addition, the different contraction rates during the C-bend formation seen in the two latency groups may imply differences in the neuronal commands. The escape responses of herring were directed away from the stimulus more often than towards it (88% of the total). These away responses were more common in long latency responses, suggesting that the latter enable herring to be more accurate in discerning the direction of the threat. Startled fish contracting their body towards the stimulus (performing a towards response) appear to correct their escape course, since their escape trajectory distribution is non-uniformty distributed around 360° and directed away from the stimulus. We hypothesize that when herring are schooling, the ability of each fish to correct its trajectory following turns towards the stimulus is enhanced.

SUMMARY Inter-individual variation in physiological performance traits, which is stable over time, can be of potential ecological and evolutionary significance. The fish escape response is interesting in this regard because it is a performance trait for which inter-individual variation may determine individual survival. The temporal stability of such variation is, however, largely unexplored. We quantified individual variation of various components of the escape response in a population of European sea bass (Dicentrarchus labrax), considering both non-locomotor (responsiveness and latency) and locomotor (speed, acceleration, turning rate, turning angle and distance travelled in a fixed time, Desc) variables. We assessed whether variation in performance was temporally stable and we searched for any trade-offs among the components of the response that might explain why the variation persisted in the population. The coefficient of variation was high for all components, from 23% for turning rate to 41% for Desc, highlighting the non-stereotypic nature of the response. Individual performance for all variables was significantly repeatable over five sequential responses at 30 min intervals, and also repeatable after a 30 day interval for most of the components. This indicates that the variation is intrinsic to the individuals, but there was no evidence for trade-offs amongst the components of the response, suggesting that, if trade-offs exist, they must be against other ecologically important behavioural or performance traits.

Elevated carbon dioxide (CO 2 ) has recently been shown to affect chemosensory and auditory behaviour, and activity levels of larval reef fishes, increasing their risk of predation. However, the mechanisms underlying these changes are unknown. Behavioural lateralization is an expression of brain functional asymmetries, and thus provides a unique test of the hypothesis that elevated CO 2 affects brain function in larval fishes. We tested the effect of near-future CO 2 concentrations (880 µatm) on behavioural lateralization in the reef fish, Neopomacentrus azysron . Individuals exposed to current-day or elevated CO 2 were observed in a detour test where they made repeated decisions about turning left or right. No preference for right or left turns was observed at the population level. However, individual control fish turned either left or right with greater frequency than expected by chance. Exposure to elevated-CO 2 disrupted individual lateralization, with values that were not different from a random expectation. These results provide compelling evidence that elevated CO 2 directly affects brain function in larval fishes. Given that lateralization enhances performance in a number of cognitive tasks and anti-predator behaviours, it is possible that a loss of lateralization could increase the vulnerability of larval fishes to predation in a future high-CO 2 ocean.

Summary Escape responses are used by many animal species as their main defence against predator attacks. Escape success is determined by a number of variables; important are the directionality (the percentage of responses directed away from the threat) and the escape trajectories (ETs) measured relative to the threat. Although logic would suggest that animals should always turn away from a predator, work on various species shows that these away responses occur only approximately 50–90% of the time. A small proportion of towards responses may introduce some unpredictability and may be an adaptive feature of the escape system. Similar issues apply to ETs. Theoretically, an optimal ET can be modelled on the geometry of predator–prey encounters. However, unpredictability (and hence high variability) in trajectories may be necessary for preventing predators from learning a simple escape pattern. This review discusses the emerging trends in escape trajectories, as well as the modulating key factors, such as the surroundings and body design. The main ET patterns identified are: (1) high ET variability within a limited angular sector (mainly 90–180 deg away from the threat; this variability is in some cases based on multiple peaks of ETs), (2) ETs that allow sensory tracking of the threat and (3) ETs towards a shelter. These characteristic features are observed across various taxa and, therefore, their expression may be mainly related to taxon-independent animal design features and to the environmental context in which prey live – for example whether the immediate surroundings of the prey provide potential refuges.

The behavioural responses of wild (predator-experienced) and hatchery-reared (predator-naive) cod Gadus morhua to standardized mechano-acoustic (MA) stimuli were compared in the laboratory. Wild fish responded mainly with freezing and fast-start escapes away from the stimulus, whereas hatchery-reared fish often ignored or approached the stimulus. Wild fish also had stronger responses, turning faster during escapes and reducing activity immediately after the stimulus. Both fish types were less active on a 'risky' bare substratum after the stimulus. The antipredator responses of wild fish were consistent to repeated stimuli, whereas hatchery-reared fish that had generally only encountered harmless stimuli showed more variable responses with lower repeatability. This suggests that experience plays a role in shaping the behavioural response of fishes to MA stimuli.

Angelfish (Pterophyllum eimekei) employ two types of fast-starts, single bend (SB) and double bend (DB). Higher performance (distance travelled, velocity, acceleration) and smaller angles of turn are found in DB responses than in SB responses. The percentage of DB responses is inversely related to body size. Small fish employ DB responses for all escape angles, whereas larger fish commonly show SB responses. This is due to a decrease in maximum DB escape angles for larger fish. Escape angles for pooled SB and DB responses are size-independent. Distance covered within a given time, maximum velocity, and maximum acceleration for pooled SB and DB responses are size-independent. With the exception of the smallest fish, angelfish show submaximal performance when making large turns. We suggest that angelfish employ a particular type of response depending on their predators' strike angle. Extremely small and large fish use principally DB and SB responses, respectively. The employment of SB and DB responses in small and large fish, respectively, may be restricted to a narrow range of predator strike angles.

Although fish escape trajectories are linearly related to stimulus direction, they vary considerably after the initial turn away from the stimulus. Past studies of escape trajectories in fish and other animals have been analysed by employing linear plots of stimulus angle versus body turning angle. Here, we define escape trajectories as a circular variable, with 0° as stimulus direction. Angelfish (Pterophyllum eimekei) escape in non-random trajectories when the stimulus is presented laterally, within an angular zone of approximately 30–120° (discriminating zone). The circular plot of escape trajectories shows a bimodal pattern that cannot be revealed by linear analysis. Angelfish escape preferentially at 180° and 130° away from the stimulus, maximizing the distance covered from the stimulus and escaping at the limit of their discriminating zone, respectively. Angelfish correct their responses when turning towards the stimulus, suggesting that escape trajectories are modulated by sensory feedback. Re-analysis of published work on other animals, by employing circular histograms of escape trajectories, reveals multimodal patterns which are also not apparent from the linear plots. We suggest that the presence of multiple preferred trajectories may be adaptive in preventing predators from learning any single fixed pattern of response and compensating for it.

The hypothesis of a differential effect of hypoxia on activity in shoaling v. solitary fish was tested in golden grey mullet Liza aurata. In both solitary and shoaling fish, (1) swimming activity increased significantly at

Members of the family Embiotocidae exhibit a distinct gait transition from exclusively pectoral fin oscillation to combined pectoral and caudal fin propulsion with increasing swimming speed. The pectoral–caudal gait transition occurs at a threshold speed termed U p–c. The objective of this study was to partition aerobic and anaerobic swimming costs at speeds below and above the U p–c in the striped surfperch Embiotoca lateralis using swimming respirometry and video analysis to test the hypothesis that the gait transition marks the switch from aerobic to anaerobic power output. Exercise oxygen consumption rate was measured at 1.4, 1.9 and 2.3 L s–1. The presence and magnitude of excess post-exercise oxygen consumption (EPOC) were evaluated after each swimming speed. The data demonstrated that 1.4 L s–1 was below the U p–c, whereas 1.9 and 2.3 L s–1 were above the U p–c. These last two swimming speeds included caudal fin propulsion in a mostly steady and unsteady (burst-assisted) mode, respectively. There was no evidence of EPOC after swimming at 1.4 and 1.9 L s–1, indicating that the pectoral–caudal gait transition was not a threshold for anaerobic metabolism. At 2.3 L s–1, E. lateralis switched to an unsteady burst and flap gait. This swimming speed resulted in EPOC, suggesting that anaerobic metabolism constituted 25% of the total costs. Burst activity correlated positively with the magnitude of the EPOC. Collectively, these data indicate that steady axial propulsion does not lead to EPOC whereas transition to burst-assisted swimming above U p–c is associated with anaerobic metabolism in this labriform swimmer. * COT : cost of transport EPOC : excess post-exercise oxygen consumption f b : burst frequency f c : caudal fin beat frequency f p : pectoral fin beat frequency L F : fork length L S : standard length ![Graphic][1] : oxygen consumption rate RMR : routine metabolic rate U : swimming speed U crit : critical swimming speed U opt : optimum swimming speed U p–c : pectoral–caudal gait transition speed [1]: /embed/inline-graphic-32.gif

Copyright by the Ecological Society of America, Marine reserves are assumed to protect a wide range of species from deleterious effects stemming from exploitation. However, some species, due to their ecological characteristics, may not respond positively to protection. Very little is known about the effects of life history and ecological traits (e.g., mobility, growth, and habitat) on responses of fish species to marine reserves. Using 40 data sets from 12 European marine reserves, we show that there is significant variation in the response of different species of fish to protection and that this heterogeneity can be explained, in part, by differences in their traits. Densities of targeted size-classes of commercial species were greater in protected than unprotected areas. This effect of protection increased as the maximum body size of the targeted species increased, and it was greater for species that were not obligate schoolers. However, contrary to previous theoretical findings, even mobile species with wide home ranges benefited from protection: the effect of protection was at least as strong for mobile species as it was for sedentary ones. Noncommercial bycatch and unexploited species rarely responded to protection, and when they did (in the case of unexploited bentho-pelagic species), they exhibited the opposite response: their densities were lower inside reserves. The use of marine reserves for marine conservation and fisheries management implies that they should ensure protection for a wide range of species with different life-history and ecological traits. Our results suggest this is not the case, and instead that effects vary with economic value, body size, habitat, depth range, and schooling behavior., Sí

Escape responses are used by most fish species in order to avoid predation. Escape responses include a number of behavioral and kinematic components, such as responsiveness, reaction distance, escape latency, directionality, and distance-derived performance. All of these components can contribute to escape success. Work on the context-dependent variability has focused on reaction distance, and suggests that this component is largely determined by the relative cost and benefits of escaping (economic hypothesis). For example, reaction distance was found to depend on many factors related to perceived risk and cost of escaping, such as the attack speed and size of the predators, the proximity to refuges, and engagement in other activities (e.g., feeding). Evidence from many behavioral, kinematic, and physiological studies suggest that performance in other components of the escape response is also not always maximized. For example, escape latencies may increase in the presence of schooling neighbors, and escape speed is higher in fish that have been subject to higher predation pressure. In addition, all escape components are further modulated by the effect of environmental factors. Variability in escape components can be interpreted by using both ultimate and proximate explanations, for example, the effect of stimulus strength on escape latency can be interpreted as the triggering neural threshold varying with stimulus strength (proximate explanation) and high intensity stimuli representing higher risk to the prey (ultimate explanation). An integrative approach is suggested for a full, ecologically relevant, assessment of escape performance in fish.

SUMMARYThe adoption of postures as a response to threats is often interpreted in terms of predator detection or signalling (e.g. vigilance and defence display). The possibility that an alternative or additional function of anti-predator postures might be to enhance the subsequent escape has been largely unexplored. Here, we use black goby (Gobius niger) to test the hypothesis that a postural curvature caused by a bending response (i.e. a slow muscle contraction which bends the body with no forward displacement)induced by a weak stimulus (WS) may affect escape responses. Three experiments were carried out. (1) Control and WS-stimulated fish were startled using lateral mechanical stimuli, to test whether the orientation of the postural C-bend affected escape direction and performance. Postural curvature was defined as positive when escapes were towards the convex side of the postural C-shape, and negative when they were towards the concave side. Locomotor performance increased with postural curvature, although fish showed a preference for escaping away from the stimulus regardless of postural curvature. (2) Control and WS-stimulated fish were startled from above, hence minimising the directionality of the threat on the horizontal plane. WS-stimulated fish showed a bias towards escaping from a positive curvature,thereby enhancing their locomotor performance. (3) Field observations with stimuli coming from above showed that gobies escape most often towards the convex side of the postural C-shape. By escaping from positively curved postures, most of the initial tailsweep is directed backwards and may provide more thrust than when starting from straight or negatively curved postures. Hence, the anti-predator posture adopted by alerted benthic fishes may`prepare' them for their subsequent escape response because it conveys an advantage when they are attacked from above (a likely occurrence), although when gobies are stimulated horizontally, escape direction may be favoured over high locomotor performance when the two trade off.

The fast-start escape response in fish is essential for predator avoidance, but almost nothing is known about whether sublethal concentrations of pollutants can impair this reflex. Ammonia, a pervasive pollutant of aquatic habitats, is known to have toxic effects on nervous and muscle function in teleost fish. Golden gray mullet (Liza aurata L.) were exposed for 24 h to sublethal ammonia concentrations in seawater (control, 400 micromol L(-1), or 1,600 micromol L(-1) NH(4)Cl), and then their response to startling with a mechanical stimulus was measured with high-speed video. Initiation of the escape response was significantly slowed by ammonia exposure: response latency rose proportionally from50 ms in controls to300 ms at a concentration of 1,600 micromol L(-1 ) NH(4)Cl. This indicates toxic effects on nervous function within the reflex arc. Impaired escape performance was also observed: maximum turning rate, distance covered, velocity, and acceleration were significantly reduced by45% at a concentration of 1,600 micromol L(-1) NH(4)Cl. This indicates toxic effects on fast-twitch glycolytic white muscle function, the muscle type that powers the fast-start response. These neuromotor impairments were associated with significant ammonia accumulations in venous plasma and white muscle and brain tissue. These results indicate that anthropogenic ammonia pollution in aquatic habitats may increase the vulnerability of fish to predation, especially by birds and mammals that are not affected by water ammonia concentrations.

Summary The short-lived annual fish Nothobranchius furzeri shows extremely short captive life span and accelerated expression of age markers, making it an interesting model system to investigate the effects of experimental manipulations on longevity and age-related pathologies. Here, we tested the effects of dietary restriction (DR) on mortality and age-related markers in N. furzeri . DR was induced by every other day feeding and the treatment was performed both in an inbred laboratory line and a longer-lived wildderived line. In the inbred laboratory line, DR reduced age-related risk and prolonged maximum life span. In the wild-derived line, DR induced early mortality, did not reduce general age-related risk and caused a small but significant extension of maximum life span. Analysis of agedependent mortality revealed that DR reduced demographic rate of aging, but increased baseline mortality in the wildderived strain. In both inbred- and wild-derived lines, DR prevented the expression of the age markers lipofuscin in the liver and Fluoro-Jade B (neurodegeneration) in the brain. DR also improved performance in a learning test based on conditioning (active avoidance in a shuttle box). Finally, DR induced a paradoxical up-regulation of glial fibrillary acidic protein in the brain.

The kinematics of turning manoeuvres and the distance-time performance in escape responses of startled angelfish (Pterophyllum eimekei) are investigated employing high-speed cinematography (400Hz). All escape responses observed are C-type fast-starts, in which the fish assumes a C shape at the end of the initial body contraction (stage 1). Kinematic analysis of the subsequent stage (stage 2) allows the response to be classified into two types: single bend (SB), in which the tail does not recoil completely after the formation of the C, and double bend (DB), in which it does. The two types of response have different total escape angles (measured from the subsequent positions of the centre of mass, SB 120·0°; DB 73·3°, P Distance-time performance is also different in the two response types, mainly because of differences in stage 2 (maximum velocity for SB 0

Antipredator behavior is vital for most animals and calls for accurate timing and swift motion. Whereas fast reaction times [1] and predictable, context-dependent escape-initiation distances [2] are common features of most escape systems, previous work has highlighted the need for unpredictability in escape directions, in order to prevent predators from learning a repeated, fixed pattern [3,4,5]. Ultimate unpredictability would result from random escape trajectories. Although this strategy would deny any predictive power to the predator, it would also result in some escape trajectories toward the threat. Previous work has shown that escape trajectories are in fact generally directed away from the threat, although with a high variability [5,6,7,8]. However, the rules governing this variability are largely unknown. Here, we demonstrate that individual cockroaches (Periplaneta americana, a much-studied model prey species [9,10,11,12,13,14]) keep each escape unpredictable by running along one of a set of preferred trajectories at fixed angles from the direction of the threatening stimulus. These results provide a new paradigm for understanding the behavioral strategies for escape responses, underscoring the need to revisit the neural mechanisms controlling escape directions in the cockroach and similar animal models, and the evolutionary forces driving unpredictable, or ?protean? [3], antipredator behavior.

The success of MPAs in conserving fishing resources and protecting marine biodiversity relies strongly on how well they meet their planned (or implicit) management goals. From a review of empirical studies aiming at assessing the ecological effects of Mediterranean and Macaronesian MPAs, we conclude that establishing an MPA is successful for (i) increasing the abundance/biomass, (ii) increasing the proportion of larger/older individuals, and (iii) enhancing the fecundity of commercially harvested populations; also, MPAs demonstrated to be effective for (iv) augmenting local fishery yields through biomass exportation from the protected area, and (v) inducing shifts in fish assemblage structure by increasing the dominance of large predator species. However, the attraction for tourism and diving due to ecological benefits of protection can cause damages likely to reverse some of the MPA effects. Other expected effects are more subject to uncertainty, and hence need more research, such as (vi) causing density-dependent changes in life history traits and (vii) protecting the recruitment of commercially important species, (viii) protecting marine biodiversity (including genetic diversity), (ix) causing ecosystem-wide effects such as trophic cascades, and (x) increasing community and ecosystem stability, thus promoting resilience and faster recovery from disturbance. Meta-analysis of data arising from these case studies are used to establish the overall effect of MPAs, and its relationship to MPA features, such as size of no-take area or time since protection. Based on the review and the meta-analyses, specific recommendations are provided for MPA management, regarding the establishment of goals and objectives, site selection, MPA design and zoning, planning, and monitoring. Finally, a series of recommendations for MPA research are offered to drive future research in MPA issues in the Mediterranean and Macaronesia., peer-reviewed

Hypoxia is a phenomenon occurring in marine coastal areas with increasing frequency. While hypoxia has been documented to affect fish activity and metabolism, recent evidence shows that hypoxia can also have a detrimental effect on various antipredator behaviours. Here, we review such evidence with a focus on the effect of hypoxia on fish escape responses, its modulation by aquatic surface respiration (ASR) and schooling behaviour. The main effect of hypoxia on escape behaviour was found in responsiveness and directionality. Locomotor performance in escapes was expected to be relatively independent of hypoxia, since escape responses are fuelled anaerobically. However, hypoxia decreased locomotor performance in some species (Mugilidae) although only in the absence of ASR in severe hypoxia. ASR allows fish to show higher escape performance than fish staying in the water column where hypoxia occurs. This situation provides a trade-off whereby fish may perform ASR in order to avoid the detrimental effects of hypoxia, although they would be subjected to higher exposure to aerial predation. As a result of this trade-off, fishes appear to minimize surfacing behaviour in the presence of aerial predators and to surface near shelters, where possible.For many fish species, schooling can be an effective antipredator behaviour. Severe hypoxia may lead to the disruption of the school unit. At moderate levels, hypoxia can increase school volume and can change the shuffling behaviour of individuals. By altering school structure and dynamics, hypoxia may affect the well functioning of schooling in terms of synchronization and execution of antipredator manoeuvres. School structure and volume appear to be the results of numerous trade-offs, where school shape may be dictated by the presence of predators, the need for energy saving via hydrodynamic advantages and oxygen level.The effects of hypoxia on aquatic organisms can be taxon specific. While hypoxia may not necessarily increase the vulnerability of fish subject to predation by other fish (since feeding in fish also decreases in hypoxia), predators from other taxa such as birds, jellyfish or aquatic mammals may take advantage of the detrimental effects of hypoxia on fish escape ability. Therefore, the effect of hypoxia on fish antipredator behaviours may have major consequences for the composition of aquatic communities.

Environmental constraints in aquatic habitats have become topics of concern to both the scientific community and the public at large. In particular, coastal and freshwater habitats are subject to dramatic variability in various environmental factors, as a result of both natural and anthropogenic processes. The protection and sustainable management of all aquatic habitats requires greater understanding of how environmental constraints influence aquatic organisms. Locomotion and predator–prey interactions are intimately linked and fundamental to the survival of mobile aquatic organisms. This paper summarizes the main points from the review and research articles which comprise the theme issue ‘Environmental constraints upon locomotion and predator–prey interactions in aquatic organisms’. The articles explore how natural and anthropogenic factors can constrain these two fundamental activities in a diverse range of organisms from phytoplankton to marine mammals. Some major environmental constraints derive from the intrinsic properties of the fluid and are mechanical in nature, such as viscosity and flow regime. Other constraints derive from direct effects of factors, such as temperature, oxygen content of the water or turbidity, upon the mechanisms underlying the performance of locomotion and predator–prey interactions. The effect of these factors on performance at the tissue and organ level is reflected in constraints upon performance of the whole organism. All these constraints can influence behaviour. Ultimately, they can have an impact on ecological performance. One issue that requires particular attention is how factors such as temperature and oxygen can exert different constraints on the physiology and behaviour of different taxa and the ecological implications of this. Given the multiplicity of constraints, the complexity of their interactions, and the variety of biological levels at which they can act, there is a clear need for integration between the fields of physiology, biomechanics, behaviour, ecology, biological modelling and evolution in both laboratory and field studies. For studies on animals in their natural environment, further technological advances are required to allow investigation of how the prevailing physico-chemical conditions influence basic physiological processes and behaviour.

Swimming is critical to the ecology of many fishes as it determines, for example, their ability to forage, to escape predators, and to migrate. The information about locomotion in primitive fishes is, however, sparse and unevenly distributed. For example, sustained exercise performance has been studied in the primitive groups with a migratory lifestyle such as lampreys and sturgeons, whereas fast‐start performance has been investigated in sit‐and‐wait predators such as the bichirs and gars. Very little is known about locomotion in lungfishes, typically considered rather sedentary species. The lamprey has been a model for studies of the neural circuits that drive axial locomotion, but this information has yet to be put into a clear evolutionary context relative to other fishes. Indeed, there have been relatively few studies aimed explicitly at investigating the evolution of locomotor performance in primitive fishes, aside from some studies on startle behaviors. Great caution should be exercised when making literature‐based comparisons between “the teleosts” and single primitive species, or discrete phylogenetic groups with particular life histories and morphologies (e.g., sturgeons). The evidence does indicate, however, that primitive fishes perform exercise less well than teleosts with similar lifestyles. This is true for swimming endurance, critical speed swimming, and fast starts. Thus, the evolution of fishes to the teleosts has, in fact, been associated with evolution of “better” exercise performance. It is tempting to speculate that improved locomotor ability might have contributed to the dominance of the teleosts today.

In hypoxia, gray mullet surface to ventilate well-oxygenated water in contact with air, an adaptive response known as aquatic surface respiration (ASR). Reflex control of ASR and its behavioral modulation by perceived threat of aerial predation and turbid water were studied on mullet in a partly sheltered aquarium with free surface access. Injections of sodium cyanide (NaCN) into either the bloodstream ( internal) or ventilatory water stream ( external) revealed that ASR, hypoxic bradycardia, and branchial hyperventilation were stimulated by chemoreceptors sensitive to both systemic and water O-2 levels. Sight of a model avian predator elicited bradycardia and hypoventilation, a fear response that inhibited reflex hyperventilation following external NaCN. The time lag to initiation of ASR following NaCN increased, but response intensity ( number of events, time at the surface) was unchanged. Mullet, however, modified their behavior to surface under shelter or near the aquarium edges. Turbid water abolished the fear response and effects of the predator on gill ventilation and timing of ASR following external NaCN, presumably because of reduced visibility. However, in turbidity, mullet consistently performed ASR under shelter or near the aquarium edges. These adaptive modulations of ASR behavior would allow mullet to retain advantages of the chemoreflex when threatened by avian predators or when unable to perceive potential threats in turbidity.

SUMMARY The visual plankivorous feeding behaviour of the shiner perch(Cymatogaster aggregata) was investigated by means of a flow tank operated at various current speeds. Artemia salina was used as prey. In a second set of experiments, Artemia was darkened with black ink,to compare the visually mediated behaviour of C. aggregata while feeding on dark prey vs feeding on natural (i.e. semi-transparent)prey. The positions of the fish and its prey at the time of the feeding reaction of C. aggregata were measured in three dimensions. Prey were on average closer and more in line with the fish's axis when feeding reactions to darkened Artemia were considered, in comparison with natural Artemia. Three potential mechanisms triggering the feeding reaction of C. aggregata were explored: the prey may trigger a reaction in C. aggregata when it reaches a threshold (1) angular size, (2)angular velocity, or (3) rate of change of the angular size (i.e. loom) of the prey as it is carried passively by the current towards the fish. Our results show that angular velocity may trigger the fish's reaction when using semi-transparent prey, while loom may trigger the reaction to darkened prey. This suggests that feeding behaviour of planktivorous fish is flexible and can use different cues to trigger a motor reaction to prey with different visual characteristics. The feeding reaction appeared to occur at longer distances for semi-transparent rather than darkened Artemia. We suggest that semi-transparent Artemia were visible at greater distances because of their higher scattering (i.e. diffuse reflectance) that made them appear brighter when viewed against a dark background.

SUMMARYThe locomotor performance of dogfish during escape responses was observed by means of high-speed video. Dogfish show C-type escape responses that are comparable with those shown previously in teleosts. Dogfish show high variability of turning rates of the anterior part of the body (head to centre of mass), i.e. with peak values from 434 to 1023 deg. s-1. We suggest that this variability may be due to the presence of two types of escape manoeuvres, i.e. responses with high and low turning rates, as previously found in a teleost species. Fast responses (i.e. with high maximum turning rates, ranging between 766 and 1023 deg. s-1) showed significantly higher locomotor performance than slow responses (i.e. with low maximum turning rates, ranging between 434 and 593 deg. s-1) in terms of distance covered, speed and acceleration, although no differences were found in the turning radius of the centre of mass during the escape manoeuvres. The existence of two types of escape responses would have implications in terms of both neural control and muscular activation patterns. When compared with literature data for the locomotor performance of bony fishes, dogfish showed relatively low speed and acceleration, comparable turning rates and a turning radius that is in the low part of the range when compared with teleosts, indicating relatively high manoeuvrability. The locomotor performance observed in dogfish is consistent with their morphological characteristics: (1) low locomotor performance associated with low thrust developed by their relatively small posterior depth of section and(2) relatively high manoeuvrability associated with their high flexibility.

The specific turning radius of yellowfin tuna Thunnus albacares Cuvier is large relative to that of other fish (0.47 total body length ± 0.18, mean ± 2 s.e.). We argue that specializations for efficient steady swimming compromise performance in transient turning manoeuvres.

Two samples of Aphanius fasciatus collected in the Pilo pond (northern Sardinia, Italy) and in an adjacent pool of small surface area were analysed morphologically (235 individuals) and genetically (a subsample of 58 individuals). The aims of the present study were (i) to test the hypothesis that different predation pressures may be associated with morphological and/or genetic differences between samples from each habitat and (ii) to assess the level of divergence between the two populations. Morphological analysis was based on the relative size of fins because it has been shown to be associated with predation pressure. The relative caudal fin area (caudal fin area/total body surface) was smaller in specimens from the pool, in both males and females, whereas no differences were found for the dorsal and anal fin areas. Caudal fins with higher aspect ratio (fin depth/fin length) were found in fish from the pool but not in the pond, due to a higher fin depth. We hypothesised that specimens from the pool would show smaller caudal fin area, since they are subject to lower predation pressure. Random amplification of polymorphic DNA (RAPD) analysis revealed a relatively high degree of both within- and between-sample genetic heterogeneity. The pond and pool samples exhibited heterozygosities, which did not differ significantly by t-test. Between-sample genetic divergence was highlighted by the coancestry coefficient (theta = 0.301 +/- 0.059, P < 0.001) and analysis of molecular variance (AMOVA) (variance between sites = 41%, P < 0.001). Genetic divergence between sites with a relatively high genetic diversity within both samples suggested that the population in the pool did not originate from a single colonisation event with a small number of founders. The genetic divergence between the two populations is consistent with their differences in fin size., Deux échantillons de l’espèce Aphanius fasciatus, collectés dans l’étang de Pilo (nord de la Sardaigne, Italie) et dans une mare voisine, ont été analysés morphologiquement (235 individus) et génétiquement (un sous-échantillon de 58 individus). Les objectifs sont : 1) de tester l’hypothèse selon laquelle des pressions de prédation différentes seraient associées à des différences morphologiques et/ou génétiques entre les échantillons de chaque habitat ; 2) de déterminer le niveau de divergence entre les deux populations. L’analyse morphologique est basée sur la taille relative des nageoires car il a été démontré qu’elle dépendait de la pression de prédation. La surface relative de la nageoire caudale (surface de la nageoire caudale/surface totale du corps) est plus petite chez les spécimens de la mare aussi bien chez les mâles que chez les femelles alors qu’aucune différence n’est trouvée pour les surfaces des nageoires dorsale et anale. Les nageoires caudales à l’aspect plus haut (profondeur/longueur) se rencontrent chez les poissons de la mare mais pas chez celle de l’étang. Nous supposions que les spécimens de la mare présenteraient une surface de la nageoire caudale inférieure puisqu’ils sont soumis à une moindre pression de prédation. Une analyse par la méthode random amplification of polymorphic DNA (RAPD) révèle un degré d’hétérogénéité génétique relativement élevé aussi bien au sein d’un échantillon qu’entre les échantillons. Les échantillons de l’étang et de la mare présentent des hétérozygoties qui ne diffèrent pas significativement en utilisant le test-t. La divergence entre échantillons est mise en lumière par le coefficient de co-lignage (θ = 0,301 ± 0,059, P < 0,001) et le test Amova (variance entre sites = 41 %, P < 0,001). La divergence génétique entre sites avec une diversité génétique relativement élevée au sein des deux échantillons suggère que la population de la mare n’est pas issue d’une seule colonisation avec un faible nombre de fondateurs. La divergence génétique entre les deux populations est cohérente avec la différence de taille de leurs nageoires.

The effect of progressive hypoxia on the structure and dynamics of herring (Clupea harengus) schools in laboratory conditions was investigated. The length, width and depth of schools of about 20 individuals were measured from video recordings to test the hypothesis that during hypoxia fish schools change their shape and volume. School shape (calculated as the ratios of length/depth, width/depth and length/width) did not change significantly during hypoxia. School length, width, depth, area and volume were all significantly increased at 20% oxygen saturation. Volume, area and width were more sensitive to hypoxia; volume and width were also increased at 25% and area at 30% oxygen saturation. The degree of position changing (shuffling) of individuals within the school was also analysed. Shuffling in normoxia was observed to occur largely through 'O-turn' manoeuvres, a 360( degrees )turn executed laterally to the school that allowed fishes in the front to move to the back. O-turn frequency during normoxia was 0.69 O-turns fish(-1) min(-1) but significantly decreased with hypoxia to 0.37 O-turns fish(-1) min(-1) at 30% oxygen saturation. Shuffling was also investigated by measuring the persistence time of individual herring in leading positions (i.e. the first half of the school). No significant changes occurred during hypoxia, indicating that the decrease in O-turn frequency does not affect shuffling rate during hypoxia, and that position shuffling in hypoxic conditions is mainly due to overtaking or falling back by individual fishes. School integrity and positional dynamics are the outcome of trade-offs among a number of biotic factors, such as food, predator defence, mating behaviour and various physical factors that may impose certain limits. Among these, our results indicate that oxygen level modulates schooling behaviour. Oxygen alters whole-school parameters at oxygen saturation values that can be encountered by herring in the field, indicating that oxygen availability is an important factor in the trade-offs that determine school volume. An increase in school volume in the wild may increase the oxygen available to each individual. However, shuffling rate is not affected by hypoxia, indicating that the internal dynamics of positioning is the result of the balance of other factors, for example related to the nutritional state of each individual fish as suggested by previous studies.

Recent studies have shown that elevated CO2 can affect the behaviour of larval and juvenile fishes. In particular, behavioural lateralization, an expression of brain functional asymmetries, is affected by elevated CO2 in both coral reef and temperate fishes. However, the potentially interacting effects of rising temperatures and CO2 on lateralization are unknown. Here, we tested the combined effect of near-future elevated-CO2 concentrations (930 µatm) and temperature variation on behavioural lateralization of a marine damselfish, Pomacentrus wardi. Individuals exposed to one of four treatments (two CO2 levels and two temperatures) were observed in a detour test where they made repeated decisions about turning left or right. Individuals exposed to current CO2 and ambient temperature levels showed a significant right-turning bias at the population level. This biased was reversed (i.e. to the left side) in fish exposed to the elevated-CO2 treatment. Increased temperature attenuated this effect, resulting in lower values of relative lateralization. Consequently, rising temperature and elevated CO2 may have different and interactive effects on behavioural lateralization and therefore future studies on the effect of climate change on brain functions need to consider both these critical variables in order to assess the potential consequences for the ecological interactions of marine fishes.

Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO 2 ) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO 2 levels (961 µatm) impair this escape behaviour during a predator–prey interaction. Elevated-CO 2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO 2 indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO 2 , as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO 2 levels could have potentially far-reaching implications for marine ecosystems.

During predator-prey encounters, a high locomotor performance in unsteady manoeuvres (i.e. acceleration, turning) is desirable for both predators and prey. While speed increases with size in fish and other aquatic vertebrates in continuous swimming, the speed achieved within a given time, a relevant parameter in predator-prey encounters, is size independent. In addition, most parameters indicating high performance in unsteady swimming decrease with size. Both theoretical considerations and data on acceleration suggest a decrease with body size. Small turning radii and high turning rates are indices of maneuverability in space and in time, respectively. Maneuverability decreases with body length, as minimum turning radii and maximum turning rates increase and decrease with body length, respectively. In addition, the scaling of linear performance in fish locomotion may be modulated by turning behaviour, which is an essential component of the escape response. In angelfish, for example, the speed of large fish is inversely related to their turning angle, i.e. fish escaping at large turning angles show lower speed than fish escaping at small turning angles. The scaling of unsteady locomotor performance makes it difficult for large aquatic vertebrates to capture elusive prey by using whole-body attacks, since the overall maneuverability and acceleration of small prey is likely to be superior to that of large predators. Feeding strategies in vertebrate predators can be related to the predator-prey length ratios. At prey-predator ratios higher than approximately 10(-2), vertebrate predators are particulate feeders, while at smaller ratios, they tend to be filter feeders. At intermediate ratios, large aquatic predators may use a variety of feeding methods that aid, or do not involve, whole body attacks. Among these are bubble curtains used by humpback whales to trap fish schools, and tail-slapping of fish by delphinids. Tail slapping by killer whales is discussed as an example of these strategies. The speed and acceleration achieved by the flukes of killer whales during tail slaps are higher and comparable, respectively, to those that can be expected in their prey, making tail-slapping an effective predator behaviour.

Escape responses consist of sudden accelerations as reactions to threatening stimuli and are present in most animals as a means of avoiding predation. Escape responses are currently receiving increased attention as valuable models for animal behavior, ecology, and neurobiology. The path along which an animal moves during an escape response (its escape trajectory) has attracted the interest of ecologists and behaviorists in relation to its functional role in predator–prey interactions. Escape trajectories (ETs) as considered in this article refer to the initial prey response to a predator’s attack. Such a trajectory should be measured at the end of the main rotational motion present during the escape response, which usually corresponds to a specific kinematic stage of the animal’s locomotion. Beyond this stage, prey may continue escaping along a zigzag path, especially if predators follow up their attack with a chase. Keywords: stimuli; circular data; avoidence; binomial distrbution

The cerci of the cockroach are covered with identified sensory hairs, which detect air movements. The sensory neurons which innervate these hairs synapse with giant interneurons (GIs) in the terminal ganglion which in turn synapse with interneurons and leg motorneurons in thoracic ganglia. This neural circuit mediates the animal's escape behavior. The transcription factor Engrailed (En) is expressed only in the medially born sensory neurons, which suggested it could work as a positional determinant of sensory neuron identity. Previously, we used RNA interference (RNAi) to abolish En expression, and found that the axonal arborization and synaptic outputs of an identified En-positive sensory neuron changed so that it came to resemble a nearby En-negative cell, which was itself unaffected. We thus demonstrated directly that En controls synaptic choice, as well as axon projections. Is escape behavior affected as a result of this mis-wiring? Adult cockroaches keep each escape unpredictable by running along one of a set of preferred escape trajectories (ETs) at fixed angles from the direction of the threatening stimulus. The probability of selecting a particular ET is influenced by wind direction. Early instar juvenile cockroaches use the same ETs as the adults and are amenable to RNAi. En knockout significantly perturbs the animals' perception of posterior wind, altering the choice of ETs to one more appropriate for anterior wind. This is the first time that it has been shown that knockout of a transcription factor controlling synaptic connectivity can alter the perception of a directional stimulus.

The curve walking of freely moving crayfish trained to walk along a curved path during homing behaviour was investigated using a video-analysis system. The leg kinematics and leg phase relationships, as well as the relationship between stepping patterns and body axis rotation measured relative to external references, were studied. The anterior and posterior extreme positions of the power stroke (AEP and PEP, respectively) and step amplitudes were analysed. As in a previous study on crayfish curve walking on a treadmill, PEPs were more posterior in outer legs (the legs on the outside of the turn) than in the inner legs. As a result, outer legs showed larger step amplitudes than inner legs. Leg kinematics varied within each walking sequence. AEP leg angles (the angles between the body and leg axes at the AEP) tended to decrease over time for inner legs and increase for outer legs. This leg angle drift was present mainly in the anterior legs and it suggests that these legs did not completely compensate for the body rotation after each step. In addition, leg angle asymmetries in a direction opposite to that of leg angle drift were observed at the start of each curve-walking sequence, suggesting that the extensive training (3 weeks) may have allowed crayfish to anticipate the leg angle drift. The rotational component of curve walking showed a discontinuous pattern, with the animal’s body axis turning towards the inside of the curve only periodically. Analysis of cross-correlation functions showed that the angular acceleration of the body axis in the direction of the turn occurred during the power strokes of inner legs 2 and 5 and outer leg 4. While the tripod formed by these three legs showed in-phase relationships, the legs of the corresponding contralateral tripod (outer legs 2 and 5 and inner leg 4) were not in phase. We hypothesize that inner legs 2 and 5 and outer leg 4 act synergically causing the inward body rotation observed in curve-walking crayfish and that some of the asymmetries found in step geometry may be a passive phenomenon due to the body rotation.

SummaryMonitoring and measuring the behaviour and movement of aquatic animals in the wild is typically challenging, though micro-accelerometer (archival or telemetry) tags now provide the means to remotely identify and quantify behavioural states and rates such as resting, swimming, and migrating, and to estimate activity and energy budgets. Most studies use low frequency (≤32 Hz) accelerometer sampling due to battery and data-archiving constraints. In this study we assessed the effect of sampling frequency (aliasing) on activity detection probability using the great sculpin (Myoxocephalus polyacanthoceaphalus) as a model species. Feeding strikes and escape responses (fast-start activities) and spontaneous movements among 7 different great sculpin were triggered, observed and recorded using a tri-axial accelerometer sampling at 100 Hz and video records. We demonstrate that multiple parameters in the time and probability domains can statistically differentiate between activities with high detection (90%) and identification (80%) probabilities. Detection probability for feeding and escape activities decreased by 50% when sampling at 30 Hz) accelerometer sampling be used in similar lab and field studies. If battery and (or) data storage is limited, we also recommend archiving the events via an on-board algorithm that determines the highest likelihood and subsequent archiving of the various event-classes of interest.