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Work carried out since the late 70s has provided key insights into the comparative biomechanics, kinematics, behaviour, and neurobiology of fish escape responses. With environmental change expected to affect the physiology and biomechanics of aquatic ectotherms, there is a growing interest in understanding how environmental stressors impact the swimming performance and behaviour of fishes during escape responses, particularly in the context of predator-prey interactions. As the study of fish swimming continues to expand, there have been repeated calls to standardise experiments and reporting practices to facilitate integrative and comparative studies. Here, we provide a set of practical guidelines for conducting, analysing, and reporting experiments on escape responses in fish, including a reporting checklist to assist authors undertaking these experiments. These resources will facilitate executing and reporting escape response experiments in a rigorous and transparent fashion, helping to advance the study of fish swimming in an era of rapid environmental change.

Accelerative manoeuvres, such as fast-starts, are crucial for fish to avoid predation. Escape responses are fast-starts that include fundamental survival traits for prey that experience high predation pressure. However, no previous study has assessed escape performance in neonate tropical sharks. We quantitatively evaluated vulnerability traits of neonate tropical sharks by testing predictions on their fast-start escape performance. We predicted (1) high manoeuvrability, given their high flexibility, but (2) low propulsive locomotion owing to the drag costs associated with pectoral fin extension during escape responses. Further, based on previous work on dogfish, Squalus suckleyi, we predicted (3) long reaction times (as latencies longer than teleosts, >20 ms). We used two-dimensional, high-speed videography analysis of mechano-acoustically stimulated neonate blacktip reef shark, Carcharhinus melanopterus (n=12), and sicklefin lemon shark, Negaprion acutidens (n=8). Both species performed a characteristic C-start double-bend response (i.e. two body bends), but single-bend responses were only observed in N. acutidens. As predicted, neonate sharks showed high manoeuvrability with high turning rates and tight turning radii (3–11% of body length) but low propulsive performance (i.e. speed, acceleration and velocity) when compared with similar-sized teleosts and S. suckleyi. Contrary to expectations, escape latencies were

We investigated the combined effects of Ocean Warming (OW), Acidification (OA) and predator cues (Non-Consumptive Effects; NCEs) of two predators with contrasting feeding-digestion strategies on the mussel Perumytilus purpuratus. We considered starfish-NCEs (partially external digestion) and snail-NCEs (internal digestion). Mussels were exposed for 13 weeks to cross-factored OA (~500 and ~1400 μatm, pCO2) and OW (~15 and ~20 °C) conditions, in the presence/absence of NCEs from one or both predators. Mussels exposed to both NCEs exhibited smaller length and buoyant weight growth than those under control or snail-NCEs conditions. Mussels exposed to starfish-NCEs exhibited smaller wet mass than control mussels. OW and starfish-NCEs in isolation or combined with snail-NCEs increased mussel oxygen consumption. Byssal biogenesis was affected by the three-factors interaction. Clearance rates were affected by the OW × OA interaction. We suggest that mainly starfish-NCEs, in isolation or interacting with OA or/and OW, can threat mussel traits and the associated community.

[Extract:] In their study, Clark et al. suggest that previous studies on the effects of elevated levels of CO2 on the behaviour of coral reef fishes are not repeatable and that ocean acidification does not impair the behaviour of coral reef fishes, even though six significant behavioural effects were detected in their study, each of which was dismissed for a different reason. They then compare the means and variances of six previous ocean acidification studies in fish with a data distribution that is derived from a multi-species compilation of their own data to conclude that the results of previous studies are statistically improbable. However, Clark et al. did not closely repeat previous studies, as they did not replicate key species, used different life stages and ecological histories and changed methods in important ways that reduce the likelihood of detecting the effects of ocean acidification.

The unique engulfment filtration strategy of microphagous rorqual whales has evolved relatively recently (

To understand how climate change stressors might affect marine organisms and support adequate projections it is important to know how multiple stressors may be modulated by the presence of other species. We evaluated the direct effects of ocean warming (OW) and ocean acidification (OA) together with non-consumptive effects (NCEs) of the predatory crab Acanthocyclus hassleri on early ontogeny fitness-related traits of the commercially important rocky-shore keystone gastropod Concholepas concholepas. We measured the response of nine traits to these stressors at either the organismal level (survival, growth, feeding rates, tenacity, metabolic rate, calcification rate) or sub-organismal level (nutritional status, ATP-supplying capacity, stress condition). C. concholepas survival was not affected by any of the stressors. Feeding rates were not affected by OW or OA; however, they were reduced in the presence of crab NCEs compared with control conditions. Horizontal tenacity was affected by the OA × NCEs interaction; in the presence of NCEs, OA reduced tenacity. The routine metabolic rate, measured by oxygen consumption, increased significantly with OW. Nutritional status assessment determined that carbohydrate content was not affected by any of the stressors. However, protein content was affected by the OA × NCEs interaction; in the absence of NCEs, OA reduced protein levels. ATP-supplying capacity, measured by citrate synthase (CS) activity, and cellular stress condition (HSP70 expression) were reduced by OA, with reduction in CS activity found particularly at the high temperature. Our results indicate C. concholepas traits are affected by OA and OW and the effects are modulated by predator risk (NCEs). We conclude that some C. concholepas traits are resilient to climate stressors (survival, growth, horizontal tenacity and nutritional status) but others are affected by OW (metabolic rate), OA (ATP-supplying capacity, stress condition), and NCEs (feeding rate). The results suggest that these negative effects can adversely affect the associated community.

Using social groups (i.e. schools) of the tropical damselfish Chromis viridis, we test how familiarity through repeated social interactions influences fast-start responses, the primary defensive behaviour in a range of taxa, including fish, sharks, and larval amphibians. We focus on reactivity through response latency and kinematic performance (i.e. agility and propulsion) following a simulated predator attack, while distinguishing between first and subsequent responders (direct response to stimulation versus response triggered by integrated direct and social stimulation, respectively). In familiar schools, first and subsequent responders exhibit shorter latency than unfamiliar individuals, demonstrating that familiarity increases reactivity to direct and, potentially, social stimulation. Further, familiarity modulates kinematic performance in subsequent responders, demonstrated by increased agility and propulsion. These findings demonstrate that the benefits of social recognition and memory may enhance individual fitness through greater survival of predator attacks., Nadler et al examined how social familiarity influences fast-start defensive responses in the tropical damselfish Chromis viridis. They showed that fish in familiar schools responded faster to threats and the behaviour of others in the school than those in unfamiliar schools, which indicates that social recognition and memory can modify fish anti-predator behaviour.

Abstract In studies of social behaviour, social bonds are usually inferred from rates of interaction or association. This approach has revealed many important insights into the proximate formation and ultimate function of animal social structures. However, it remains challenging to compare social structure between systems or time-points because extrinsic factors, such as sampling methodology, can also influence the observed rate of association. As a consequence of these methodological challenges, it is difficult to analyse how patterns of social association change with demographic processes, such as the death of key social partners. Here we develop and illustrate the use of binomial mixture models to quantitatively compare patterns of social association between networks. We then use this method to investigate how patterns of social preferences in killer whales respond to demographic change. Resident killer whales are bisexually philopatric, and both sexes stay in close association with their mother in adulthood. We show that mothers and daughters show reduced social association after the birth of the daughter’s first offspring, but not after the birth of an offspring to the mother. We also show that whales whose mother is dead associate more with their opposite sex siblings and with their grandmother than whales whose mother is alive. Our work demonstrates the utility of using mixture models to compare social preferences between networks and between species. We also highlight other potential uses of this method such as to identify strong social bonds in animal populations. Significance statement Comparing patters of social associations between systems, or between the same systems at different times, is challenging due to the confounding effects of sampling and methodological differences. Here we present a method to allow social associations to be robustly classified and then compared between networks using binomial mixture models. We illustrate this method by showing how killer whales change their patterns of social association in response to the birth of calves and the death of their mother. We show that after the birth of her calf, females associate less with their mother. We also show that whales’ whose mother is dead associate more with their opposite sex siblings and grandmothers than whales’ whose mother is alive. This clearly demonstrates how this method can be used to examine fine scale temporal processes in animal social systems.

Many vertebrate animals employ anaerobic pathways during high-speed exercise, even if it imposes an energetic cost during postexercise recovery, expressed as excess postexercise oxygen consumption (EPOC). In ectotherms such a fish, the initial anaerobic contribution to exercise is often substantial. Even so, fish may recover from anaerobic pathways as swimming exercise ensues and aerobic metabolism stabilizes, thus total energetic costs of exercise could depend on swimming duration and subsequent physiological recovery. To test this hypothesis, we examined EPOC in striped surfperch (Embiotoca lateralis) that swam at high speeds (3.25 L s-1 ) during randomly ordered 2-, 5-, 10-, and 20-min exercise periods. We found that EPOC was highest after the 2-min period (20.9 mg O2 kg-1 ) and lowest after the 20-min period (13.6 mg O2 kg-1 ), indicating that recovery from anaerobic pathways improved with exercise duration. Remarkably, EPOC for the 2-min period accounted for 72% of the total O2 consumption, whereas EPOC for the 20-min period only accounted for 14%. Thus, the data revealed a striking decline in the total cost of transport from 0.772 to 0.226 mg O2 ·kg-1 ·m-1 during 2- and 20-min periods, respectively. Our study is the first to combine anaerobic and aerobic swimming costs to demonstrate an effect of swimming duration on EPOC in fish. Clarifying the dynamic nature of exercise-related costs is relevant to extrapolating laboratory findings to animals in the wild.

This study investigated the oxygen consumption of the putative oxygen conformer marbled swamp eel Synbranchus marmoratus during progressive hypoxia. Earlier studies have not reached agreement on whether S. marmoratus is a conformer or regulator. Our results support the view that S. marmoratus is an oxygen regulator, like most bony fishes.

Fast escape responses to a predator threat are fundamental to the survival of mobile marine organisms. However, elasmobranchs are often underrepresented in such studies. Here, we measured the escape latency (time interval between the stimulus and first visible reaction) of mechanically induced escape responses in the Pacific spiny dogfish, Squalus suckleyi, and in two teleosts from the same region, the great sculpin, Myoxocephalus polyacanthocephalus, and the pile perch, Rhacochilus vacca. We found that the dogfish had a longer minimum latency (66.7 ms) compared with that for the great sculpin (20.8 ms) and pile perch (16.7 ms). Furthermore, the dogfish had a longer latency than that of 48 different teleosts identified from 35 different studies. We suggest such long latencies in dogfish may be due to the absence of Mauthner cells, the giant neurons that control fast escape responses in fishes.

International audience; We review knowledge on applications of sustained aerobic swimming as a tool to promote productivity and welfare of farmed fish species. There has been extensive interest in whether providing active species with a current to swim against can promote growth. The results are not conclusive but the studies have varied in species, life stage, swimming speed applied, feeding regime, stocking density and other factors. Therefore, much remains to be understood about mechanisms underlying findings of 'swimming-enhanced growth', in particular to demonstrate that swimming can improve feed conversion ratio and dietary protein retention under true aquaculture conditions. There has also been research into whether swimming can alleviate chronic stress, once again on a range of species and life stages. The evidence is mixed but swimming does improve recovery from acute stresses such as handling or confinement. Research into issues such as whether swimming can improve immune function and promote cognitive function is still at an early stage and should be encouraged. There is promising evidence that swimming can inhibit precocious sexual maturation in some species, so studies should be broadened to other species where precocious maturation is a problem. Swimming performance is a heritable trait and may prove a useful selection tool, especially if it is related to overall robustness. More research is required to better understand the advantages that swimming may provide to the fish farmer, in terms of production, mitigation and selection.

Fast escape responses to a predator threat are fundamental to the survival of mobile marine organisms. However, elasmobranchs are often underrepresented in such studies. Here, we measured the escape latency (time interval between the stimulus and first visible reaction) of mechanically induced escape responses in the Pacific spiny dogfish

To evade predators, many prey perform rapid escape movements. The resulting escape trajectory (ET) – measured as the angle of escape direction relative to the predator’s approach path – plays a major role in avoiding predation. Previous geometrical models predict a single ET; however, many animals (fish and other animal taxa) show highly variable ETs with multiple preferred directions. Although such a high ET variability may confer unpredictability, preventing predators from adopting counter-strategies, the reasons why animals prefer specific multiple ETs remain unclear. Here, we constructed a novel geometrical model in which Tdiff (the time difference between the prey entering the safety zone and the predator reaching that entry point) is expected to be maximized. We tested this prediction by analyzing the escape responses of Pagrus major attacked by a dummy predator. At each initial body orientation of the prey relative to the predator, our model predicts a multimodal ET with an optimal ET at the maximum Tdiff (Tdiff,1) and a suboptimal ET at a second local maximum of Tdiff (Tdiff,2). Our experiments show that when Tdiff, 1–Tdiff, 2 is negligible, the prey uses optimal or suboptimal ETs to a similar extent, in line with the idea of unpredictability. The experimentally observed ET distribution is consistent with the model, showing two large peaks at 110–130° and 170–180° away from the predator. Because various animal taxa show multiple preferred ETs similar to those observed here, this behavioral phenotype may result from convergent evolution that combines maximal Tdiff with a high level of unpredictability. Significance Statement Animals from many taxa escape from suddenly approaching threats, such as ambush predators, by using multiple preferred escape trajectories. However, the reason why these multiple preferred escape trajectories are used is still unknown. By fitting a newly constructed model to the empirical escape response data, we show that the seemingly complex multiple preferred escape trajectories can arise from a simple geometrical rule which maximizes the time difference between when the prey enters the safety zone and when the predator reaches that entry point. Our results open new avenues of investigation for understanding how animals choose their escape trajectories from behavioral and neurosensory perspectives.

© 2020. Published by The Company of Biologists Ltd. Billfishes are well known for their distinctive elongated rostra, i.e. bills. The functional significance of billfish rostra has been frequently discussed and the recent discovery of an oil gland (glandula oleofera) at the base of the rostrum in swordfish, Xiphias gladius, has added an interesting facet to this discussion regarding the potential co-evolution of gland and rostra. Here, we investigated the oil gland and oil pores (through which the oil is brought to the skin surface) of four billfish species - swordfish, Atlantic blue marlin (Makaira nigricans), Indo-Pacific sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) - and provide detailed evidence for the presence of an oil gland in the last three. All four species had a high density of oil pores on the forehead which is consistent with the hypothesis of hydrodynamic benefits of the oil. The extension of the pores onto the front half of the rostrum in sailfish and striped marlin, but not in swordfish or blue marlin, suggests that the oil may have additional functions. One such function could be linked to the antibacterial and anti-inflammatory properties of the oil. However, the available evidence on predatory rostrum use (and hence the likelihood of tissue damage) is only partly consistent with the extension of pores on rostra across species. We conclude that the oil gland probably serves multiple, non-mutually exclusive functions. More detailed information on rostrum use in blue marlin and swordfish is needed to better link behavioural and morphological data with the aim of accomplishing a full comparative analysis.

Wave-induced surge conditions are found in shallow marine ecosystems worldwide; yet, few studies have quantified how cyclical surges may affect free swimming animals. Here, we used a recently adapted respirometry technique to compare the energetic costs of a temperate fish species (Cymatogaster aggregata) swimming against a steady flow versus cyclical unidirectional and bidirectional surges in which unsteady swimming (such as accelerating, decelerating and turning) occurs. Using oxygen uptake (ṀO(2)) as an estimate of energetic costs, our results reveal that fish swimming in an unsteady (i.e. cyclical) unidirectional flow showed no clear increase in costs when compared to a steady flow of the same average speed, suggesting that costs and savings from cyclical acceleration and coasting are near equal. Conversely, swimming in a bidirectional cyclical flow incurred significantly higher energetic costs relative to a steady, constant flow, likely due to the added cost of turning around to face the changing flow direction. On average, we observed a 50% increase in ṀO(2) of fish station holding within the bidirectional flow (227.8 mg O(2) kg(−1) h(−1)) compared to a steady, constant flow (136.1 mg O(2) kg(−1) h(−1)) of the same mean velocity. Given wave-driven surge zones are prime fish habitats in the wild, we suggest the additional costs fish incur by station holding in a bidirectional cyclical flow must be offset by favourable conditions for foraging and reproduction. With current and future increases in abiotic stressors associated with climate change, we highlight the importance of incorporating additional costs associated with swimming in cyclical water flow in the construction of energy budgets for species living in dynamic, coastal habitats.

Wave-induced surge conditions are found in shallow marine ecosystems worldwide; yet, few studies have quantified how cyclical surges may affect free swimming animals. Here, we used a recently adapted respirometry technique to compare the energetic costs of a temperate fish species (Cymatogaster aggregata) swimming against a steady flow versus cyclical unidirectional and bidirectional surges in which unsteady swimming (such as accelerating, decelerating and turning) occurs. Using oxygen uptake (ṀO2) as an estimate of energetic costs, our results reveal that fish swimming in an unsteady (i.e. cyclical) unidirectional flow showed no clear increase in costs when compared to a steady flow of the same average speed, suggesting that costs and savings from cyclical acceleration and coasting are near equal. Conversely, swimming in a bidirectional cyclical flow incurred significantly higher energetic costs relative to a steady, constant flow, likely due to the added cost of turning around to face the changing flow direction. On average, we observed a 50% increase in ṀO2 of fish station holding within the bidirectional flow (227.8 mg O2 kg−1 h−1) compared to a steady, constant flow (136.1 mg O2 kg−1 h−1) of the same mean velocity. Given wave-driven surge zones are prime fish habitats in the wild, we suggest the additional costs fish incur by station holding in a bidirectional cyclical flow must be offset by favourable conditions for foraging and reproduction. With current and future increases in abiotic stressors associated with climate change, we highlight the importance of incorporating additional costs associated with swimming in cyclical water flow in the construction of energy budgets for species living in dynamic, coastal habitats.

Linking morphological differences in foraging adaptations to prey choice and feeding strategies has provided major evolutionary insights across taxa. Here, we combine behavioural and morphological approaches to explore and compare the role of the rostrum (bill) and micro-teeth in the feeding behaviour of sailfish ( Istiophorus platypterus ) and striped marlin ( Kajikia audax ) when attacking schooling sardine prey. Behavioural results from high-speed videos showed that sailfish and striped marlin both regularly made rostrum contact with prey but displayed distinct strategies. Marlin used high-speed dashes, breaking schools apart, often contacting prey incidentally or tapping at isolated prey with their rostra; while sailfish used their rostra more frequently and tended to use a slower, less disruptive approach with more horizontal rostral slashes on cohesive prey schools. Capture success per attack was similar between species, but striped marlin had higher capture rates per minute. The rostra of both species are covered with micro-teeth, and micro-CT imaging showed that species did not differ in average micro-tooth length, but sailfish had a higher density of micro-teeth on the dorsal and ventral sides of their rostra and a higher amount of micro-teeth regrowth, suggesting a greater amount of rostrum use is associated with more investment in micro-teeth. Our analysis shows that the rostra of billfish are used in distinct ways and we discuss our results in the broader context of relationships between morphological and behavioural feeding adaptations across species.

We evaluated the effects of projected, near future ocean acidification (OA) and extreme events of temperature (warming or cooling) on the thermal tolerance of Concholepas concholepas, a coastal benthic keystone species. Three separate trials of an experiment were conducted by exposing juvenile C. concholepas for 1 month to one of two contrasting pCO

Environmental factors add constraints to organismal performance at their extremes, but support optimal performance at energetically beneficial conditions. In aquatic environments , salinity adds costs for ion transportation to the energetic budgets of osmoregulating animals, such as teleost fishes. These additional costs may limit the available energy for important ecological traits of fishes, including maximal and optimal swimming performance, which are required for successful foraging and migration in the wild. Here, we hypothesize that swimming performance, and its related costs, will be optimized at near-isoosmotic salinity, and decline under more saline conditions. Using the euryhaline shiner perch ( Cymatogaster aggregata) as a model for coastal fishes, we determined critical swimming speeds and oxygen consumption rates during swimming at salinities of 12 g kg−1 (near-isoosmotic, brackish, S12) and 31 g kg−1 (hyperosmotic, marine, S31). Most tested metrics were unaffected by salinity, including aerobic scope, active metabolic rate and optimal swimming speed. Likewise, critical swimming speed (in body lengths per second, BL s−1) was not significantly different between fishes acclimated to S12 (4.8 ± 0.6 BL s−1) or S31 (5.1 ± 0.5 BL s−1, means ± SD, n = 5) suggesting that the fish could swim and hunt for prey equally well regardless of salinity. However, S31 conditions did cause comparatively higher oxygen consumption rates at swimming speeds from 0.5 to 1.5 BL s−1 , and a 20% increase in the extrapolated standard metabolic rate (i.e. cost of maintaining bodily functions). Our results confirm that there is an added energetic cost of salinity, but highlight that the cost of osmoregulation appears minimal relative to the energetic demands of swimming, and consequently has no effect on the maximal swimming performance of adult shiner perch. Given the strong salinity gradients naturally encountered in many coastal ecosystems, these data provide an explanation for the capacity of a coastal roaming species to move in an out of coastal habitat zones without significantly compromising their ability to hunt prey, avoid predation and migrate. As climate change locally affects environmental salinity, our results offer valuable insight towards the effects of environmental perturbations on fishes in coastal marine and estuarine habitats.

Sea urchin harvesting has rapidly expanded in the last decades. Since many sea urchin species play important ecological role, large-scale commercial sea urchin fisheries can have complex effects on benthic communities. In many temperate regions, overharvesting has compromised marine ecosystems to such an extent that reintroduction of sea urchins raised in captivity may be a valid solution for the enhancement of depleted marine wild populations. In some regions of the Mediterranean Sea, improving the growth efficiency of captive sea urchin Paracentrotus lividus to be reintroduced has become a widespread practice. However, no study has yet considered the potential behavioural effects of raising sea urchins in captivity when they are introduced in the natural environment. This study provides information about the behavioural effects of captivity on P. lividus in terms of locomotion performance, a trait that can be fundamental for responding to predators and for relocation after environmental disturbances such as currents and waves. Movements of captive-born and wild sea urchins were video-recorded and compared in (i) total exposure to external cues, (ii) partial exposure to external cues and (iii) absence of external cues. Latency of locomotion, average speed and average velocity of sea urchins showed significant differences with respect to the level of exposure and their origin (i.e. wild vs. captive-born). Our results demonstrate that captive-born sea urchins in the wild showed long latency and slower locomotor performance when compared to wild sea urchins. Conversely, the straightness-of-path and locomotion direction of captive-born and wild sea urchins were similar in natural settings. Our results therefore suggest that captive-born sea urchins suffer the negative effects of captivity when introduced in a natural environment. Understanding the factors that decrease the performance of sea urchin will be important for developing procedures aimed at minimizing the negative effect of captivity before release into the wild.

International audience; Understanding how marine organisms will be affected by global change is of primary importance to ensure ecosystem functioning and nature contributions to people. This study meets the call for addressing how life‐history traits mediate effects of ocean acidification on fish. We built a database of overall and trait‐mediated responses of teleost fish to future CO2 levels by searching the scientific literature. Using a meta‐analytical approach, we investigated the effects of projected CO2 levels by IPCC for 2050–2070 and 2100 on fish eco‐physiology and behavior from 320 contrasts on 42 species, stemming from polar to tropical regions. Moreover, since organisms may experience a mosaic of carbonate chemistry in coastal environments (e.g., in estuaries, upwelling zones and intertidal habitats), which may have higher pCO2 values than open ocean waters, we assessed responses from additional 103 contrasts on 21 fish species using pCO2 levels well above IPCC projections. Under mid‐century and end‐of‐century CO2 emission scenarios, we found multiple CO2‐dose‐dependent effects on calcification, resting metabolic rate, yolk, and behavioral performances, along with increased predation risk and decreased foraging, particularly for larvae. Importantly, many of the traits considered will not confer fish tolerance to elevated CO2 and far‐reaching ecological consequences on fish population replenishment and community structure will likely occur. Extreme CO2 levels well above IPCC projections showed effects on fish mortality and calcification, while growth, metabolism, and yolk were unaffected. CO2 exposures in short‐term experiments increased fish mortality, which in turn decreased in longer‐term exposures. Whatever the elevated CO2 levels considered, some key biological processes (e.g., reproduction, development, habitat choice) were critically understudied. Fish are an important resource for livelihoods in coastal communities and a key component for stability of marine ecosystems. Given the multiple trait‐mediated effects evidenced here, we stress the need to fill the knowledge gap on important eco‐physiological processes and to expand the number and duration of ocean acidification studies to multi‐generational, multiple stressor (e.g., warming, hypoxia, fishing), and species interactions experiments to better elucidate complex ecosystem‐level changes and how these changes might alter provisioning of ecosystem services.

When oil spills occur, behavior is the first line of defense for a fish to avoid being contaminated. We determined the avoidance threshold of the European seabass (Dicentrarchus labrax) to the water-soluble fraction (WSF) of oil using a dual-flow choice box. The results showed that a plume of 20%-diluted WSF (total polycyclic aromatic hydrocarbon [PAH] concentration: 8.54 μg L-1 ) triggered a significant avoidance response that was detected within 7.5 min of introducing WSF-contaminated water into the experimental setup. However, the ecological relevance of seabass capacity to detect and avoid WSF remains to be established. In the short term, such a response is indeed liable to reduce seabass contact time with oil-contaminated water and thus preserve their functional integrity. In the long term, however, avoidance may contribute to the displacement of a population into a possibly less auspicious environment, with consequences very similar to those of contaminant exposure, that is, disturbed population dynamics and demography. Environ Toxicol Chem 2018;37:854-859. © 2017 SETAC.

In order to make adequate projections on the consequences of climate change stressors on marine organisms, it is important to know how impacts of these stressors are affected by the presence of other species. Here we assessed the direct effects of ocean warming (OW) and acidification (OA) along with non-consumptive effects (NCEs) of a predatory crab and/or a predatory snail on the habitat-forming mussel Perumytilus purpuratus. Mussels were exposed for 10–14 weeks to contrasting pCO2 (500 and 1400 μatm) and temperature (15 and 20 °C) levels, in the presence/absence of cues from one or two predator species. We compared mussel traits at sub-organismal (nutritional status, metabolic capacity-ATP production-, cell stress condition via HSP70 expression) and organismal (survival, oxygen consumption, growth, byssus biogenesis, clearance rates, aggregation) levels. OA increased the mussels' oxygen consumption; and OA combined with OW increased ATP demand and the use of carbohydrate reserves. Mussels at present-day pCO2 levels had the highest protein content. Under OW the predatory snail cues induced the highest cell stress condition on the mussels. Temperature, predator cues and the interaction between them affected mussel growth. Mussels grew larger at the control temperature (15 °C) when crab and snail cues were present. Mussel wet mass and calcification were affected by predator cues; with highest values recorded in crab cue presence (isolated or combined with snail cues). In the absence of predator cues in the trails, byssus biogenesis was affected by OA, OW and the OA × OW and OA × predator cues interactions. At present-day pCO2 levels, more byssus was recorded with snail than with crab cues. Clearance rates were affected by temperature, pCO2 and the interaction between them. The investigated stressors had no effects on mussel aggregation. We conclude that OA, OW and the NCEs may lead to neutral, positive or negative consequences for mussels.

The effect of the presence and angular position of a refuge on the direction and kinematics of mechanically-induced escape responses was observed in staghorn sculpins Leptocottus armatus using high-speed video. The results showed that the angular position of the refuge did not affect locomotor performance (speed and acceleration), although it did affect the escape trajectories. Therefore, the angular position of a refuge can modulate the direction taken by the L. armatus during the early stages of their escape response and this response can be affected by both repulsive (i.e. threats) and attractive (i.e. refuges) points of reference.

Recent work has shown that the behaviour of marine organisms can be affected by elevated PCO2, although little is known about the effect of multiple stressors. We therefore investigated the effect of elevated PCO2 and temperature on locomotion and behaviour during prey searching in the marine gastropod Concholepas concholepas, a predator characteristic of the southeastern Pacific coast. Movement duration, decision time, route finding and lateralization were measured using a T-maze tank with a prey positioned behind a barrier. Four treatments, representing present day and near-future scenarios of ocean acidification and warming were used in rearing the individuals for 6 months. Regardless of the treatment, no significant differences were found in relative and absolute lateralization before and after exposure for 6 months. However, relative lateralization was not repeatable for animals tested after 6 months at elevated PCO2 at both experimental temperatures, whereas it was repeatable in individuals kept at the present day level of PCO2. We suggest that these effects may be related to a behavioural malfunction caused by elevated PCO2. Movement duration, decision time and route finding were not repeatable. However, movement duration and decision time increased and route finding decreased in elevated PCO2 (at 15°C), suggesting that elevated PCO2 has negative effects on the locomotor and sensory performance of C. concholepas in the presence of a prey odour, thereby decreasing their ability to forage efficiently.

The study of fish escape responses has provided important insights into the accelerative motions and fast response times of these animals. In addition, the accessibility of the underlying neural circuits has made the escape response a fundamental model in neurobiology. Fish escape responses were originally viewed as highly stereotypic all-or-none behaviours. However, research on a wide variety of species has shown considerable taxon-specific and context-dependent variability in the kinematics and neural control of escape. In addition, escape-like motions have been reported: these resemble escape responses kinematically, but occur in situations that do not involve a response to a threatening stimulus. This Review focuses on the diversity of escape responses in fish by discussing recent work on: (1) the types of escape responses as defined by kinematic analysis (these include C- and S-starts, and single- versus double-bend responses); (2) the diversity of neuromuscular control; (3) the variability of escape responses in terms of behaviour and kinematics within the context of predator−prey interactions; and (4) the main escape-like motions observed in various species. Here, we aim to integrate recent knowledge on escape responses and highlight rich areas for research. Rapidly developing approaches for studying the kinematics of swimming motion both in the lab and within the natural environment provide new avenues for research on these critical and common behaviours.

Striped seagrass meadows are formed by narrow ribbons which are elevated over the seabed and separated by channels. Limited information on the genesis and development of this morphological pattern, including the adaptive responses of associated biota, is preventing holistic insight into the functioning of such protected ecosystems. This paper assessed the structural dynamics of a Posidonia oceanica striped meadow and the distribution and 3D orientation of the associated bivalve Pinna nobilis. Our analysis of the interaction between bedforms, bottom currents, and the distribution of P. nobilis revealed that the striped seascape is the result of a self-organisation process driven by feedback interactions among seagrass growth, sediment deposition, and hydrodynamics. The results suggest that the ribbon wall is the most suitable sub-habitat for this species, because it supports the highest density of P. nobilis, compared to the meadow top and bottom. Here, specimens can take advantage of the resuspension induced by hydrodynamics and open their shells towards the current, thus enhancing food intake. Therefore, our results show that self-organisation in striped seagrass meadow affects the distributional pattern of P. nobilis, providing new insights into the autoecology of this species beyond the conservation implications for its habitat.

The ecological and economic importance of fish act as a brake on the development of chemical dispersants as operational instruments following oil spills. Although a valuable and consistent body of knowledge exists, its use in spill response is limited. The objective of the present study was to increase current knowledge base to facilitate the translation of published data into information of operational value. Thus we investigated the dose-response relationship between dispersant-treated oil exposure and ecologically relevant consequences by combining laboratory and field experiments. Effects were examined over almost a year using juveniles of the slowly growing, commercially important European sea bass (Dicentrarchus labrax). A reliable interpretation of biomarker responses requires a complete knowledge of the factors likely to affect them. Interpopulational variability is of particular importance in environmental impact assessment because biomarker responses from a population collected in an impacted area are classically compared with those collected in a clean site. Our study revealed no effect of the exposure to dispersant-treated oil on fish hypoxia tolerance and temperature susceptibility at 1 and 11 mo post exposure. Similarly, no effect of the exposure was observed on the ability of the fish to cope with environmental contingencies in the field, regardless of the dose tested. Thus we feel confident to suggest that a 48-h exposure to chemically treated oil does not affect the ability of sea bass to cope with mild environmental contingencies. Finally, investigation of interpopulation variability revealed large differences in both hypoxia tolerance and temperature susceptibility among the 2 populations tested, suggesting that this variability may blur the interpretation of population comparisons as classically practiced in impact assessment. Environ Toxicol Chem 2019;38:210-221. © 2018 SETAC.

Climate change can have a pronounced impact on the physiology and behaviour of fishes. Notably, many climate change stressors, such as global warming, hypoxia and ocean acidification (OA), have been shown to alter the kinematics of predator–prey interactions in fishes, with potential effects at ecological levels. Here, we review the main effects of each of these stressors on fish escape responses using an integrative approach that encompasses behavioural and kinematic variables. Elevated temperature was shown to affect many components of the escape response, including escape latencies, kinematics and maximum swimming performance, while the main effect of hypoxia was on escape responsiveness and directionality. OA had a negative effect on the escape response of juvenile fish by decreasing their directionality, responsiveness and locomotor performance, although some studies show no effect of acidification. The few studies that have explored the effects of multiple stressors show that temperature tends to have a stronger effect on escape performance than OA. Overall, the effects of climate change on escape responses may occur through decreased muscle performance and/or an interference with brain and sensory functions. In all of these cases, since the escape response is a behaviour directly related to survival, these effects are likely to be fundamental drivers of changes in marine communities. The overall future impact of these stressors is discussed by including their potential effects on predator attack behaviour, thereby allowing the development of potential future scenarios for predator–prey interactions., Lay summary: Climate change in the aquatic environment is leading to global warming, OA and an increase in hypoxic areas and events. Here, we review the effects of these three major stressors of climate change on the escape response of fishes and their implications for predator–prey relationships.

Hydrocarbons contamination and hypoxia are two stressors that can coexist in coastal ecosystems. At present, few studies evaluated the combined impact of these stressors on fish physiology and behavior. Here, we tested the effect of the combination of hypoxia and petrogenic hydrocarbons on the anti-predator locomotor performance of fish. Specifically, two groups of European sea bass (Dicentrarchus labrax) were exposed to clean water (Ctrl) or oil-contaminated water (Oil). Subsequently, fish of both groups were placed in normoxic (norx) or hypoxic (hyp) experimental tanks (i.e. four groups of fish were formed: Ctrl norx, Ctrl hyp, Oil norx, Oil hyp). In these tanks, escape response 2 was elicited by a mechano-acoustic stimulus and recorded with a high speed camera. Several variables were analyzed: escape response duration, responsiveness (percentage of fish responding to the stimulation), latency (time taken by the fish to initiate a response), directionality (defined as away or toward the stimulus), distance-time variables (such as speed and acceleration), maneuverability variables (such as turning rate), escape trajectory (angle of flight) and distancing of the fish from the stimulus. Results revealed (i) effects of stressors (Ctrl hyp, Oil norx and Oil hyp) on the directionality; (ii) effects of Oil norx and Oil hyp on maneuverability and (iii) effects of Oil hyp on distancing. These results suggest that individual stressors could alter the escape response of fish and that their combination could strengthen these effects. Such an impact could decrease the probability of prey escape success. By investigating the effects of hydrocarbons (and the interaction with hypoxia) on the anti-predator behavior of fish, this work increases our understanding of the biological impact of oil spill. Additionally, the results of this study are of interest for oil spill impact evaluation and also for developing new ecotoxicological tools of ecological significance.