Reactive Stress Coping Styles Research Articles

Flathead grey mullet (Mugil cephalus) juveniles exhibit consistent proactive and reactive stress coping styles

Stress coping styles (SCS) are defined as a coherent set of individual physiological and behavioural differences in stress responses that are consistent across context and over time. Nowadays, an increased attention has been paid to fish welfare in aquaculture production and to consistent behavioural response to stress in captivity, since these aspects present direct implications on fish health, quality and farming productivity. Therefore, the present study aimed to evaluate the differences between proactive and reactive stress coping styles and their consistency over time and across contexts in flathead grey mullet Mugil cephalus juveniles reared in captivity. Fish were submitted to two runs of a set of behavioural tests, with a four-months interval: one group test (risk-taking test) and three individual tests (restraining, predator and confinement tests), followed by the quantification of blood cortisol and glucose concentrations (control and post-stress). Results confirmed the existence of proactive and reactive SCS in mullet juveniles and demostrated that behavioural responses in most of the tests were consistent over time (between runs) and across contexts (among tests). Fish that crossed from the safe to the risky area in the risk-taking test also displayed higher activity and escape attempts and lower basal levels of cortisol and glucose than fish than did not cross. This work reported for the first time the consistency of stress coping styles over time and across contexts in M. cephalus juveniles. Due to the increased interest in understanding adaptive mechanisms underlying consistent individual behaviours in response to stressful situations, are of interest for the aquaculture industry to improve productive performance of this fish species. Further studies are required to investigate how different selective pressures might influence the expression and consistency of SCS over time and across contexts.

Selecting suitable behavioural tests to identify proactive and reactive stress coping styles in flathead grey mullet (Mugil cephalus) juveniles

Identifying Stress Coping Styles (SCS) in new species of interest for aquaculture has important implications for its future domestication and adaptation to captivity. Individual variability allows to select the potential positive characteristics for fish production. The main aim of this study was to identify phenotypic individual differences and characterize proactive and reactive SCS in flathead grey mullet (Mugil cephalus) juveniles by exposing fish to different stress situations and evaluating their individual and group responses to level behavioural and physiology. Juveniles were subjected to one group test (risk-taking) and five individual tests (predator, first feeding after stress, restraining, new environment and confinement). All assays were repeated twice, with a one-month interval between tests. Blood samples were taken from each individual (before and after stress) to quantify cortisol and glucose plasma concentrations. Flathead grey mullet juveniles exhibited a high inter-individual variability with two extremes of behaviours: proactive and reactive profiles that were characterized by opposed behavioural (activity time and escape attempts) and physiological (levels of cortisol and glucose) responses to stress and were consistent over time and across contexts. The flathead grey mullet juveniles showed differences in their predisposition for risk taking. Likewise, the Principal Component Analysis showed that three individual stress tests (predator, restraining and confinement tests) were reliable to characterize SCS in this fish species. This work reported for the first time the existence of stress coping styles in M. cephalus juveniles and the selection of a set of reliable behavioural tests to identify phenotypic profiles in flathead grey mullet. These results might be of interest for the aquaculture industry to improve fish welfare and health and to adjust management protocols for rearing this fish species in captivity.

Investigating the physiological response and antibody concentration of gilthead sea bream (Sparus aurata) following Vibrio anguillarum vaccination depending on the stress coping style

Stress coping styles (SCSs) are defined as coherent sets of individual physiological and behavioral differences in stress response consistent across time and context and are described in a wide range of taxa, including fishes. These differences in behavior and physiology are of great interest because they may have direct implications on animal health, welfare, and performance in farming systems, including aquaculture. In this study, the physiological responses of sea bream (Sparus aurata) from different SCSs following Vibrio anguillarum vaccination were monitored. Fish were first screened either bold or shy (proxy of proactive and reactive SCSs, respectively) using group risk-taking tests and were then injected with a vaccine against V. anguillarum. Following vaccination, the fish were implanted with an accelerometer tag to monitor their swimming activity (proxy of energy expenditure), and blood sampling was carried out to measure health and welfare parameters (e.g., cortisol, glucose, hemoglobin) and aspecific immunity (e.g., protease, total proteins). In addition, blood was also collected at three different sampling times to screen antibody levels and, thus, to evaluate the efficiency of the vaccine. Following vaccination, bold fish displayed lower swimming activity values, indicative of lower energy expenditure, and also displayed higher levels of hematocrit, total proteins, and lysozyme in the plasma than the shy ones, which could be indicative of better health/welfare status and greater aspecific immunity. Finally, the V. anguillarum vaccination appeared to be more efficient in bold fish since the number of total antibodies was found higher than in shy fish 1 month after vaccination. Such results could help improve both health/welfare and productivity of farmed sea breams by selecting more robust fish, better adapted to farming conditions.

Phenotypic stress response does not influence the upper thermal tolerance of male Atlantic salmon (Salmo salar).

Fish can be identified as either low responders (LR) or high responders (HR) based on post-stress cortisol levels and whether they exhibit a proactive or reactive stress coping style, respectively. In this study, male Atlantic salmon (Salmo salar) from 17 families reared at 9°C were repeatedly exposed to an acute handling stress over a period of four months, with plasma cortisol levels measured at 1h post-stress. Fish were identified as either LR or HR if the total Z-score calculated from their cortisol responses fell into the lower or upper quartile ranges, respectively; with intermediate responders (IR) classified as the remainder. Salmon characterized as LR, IR or HR were then subjected to an incremental thermal challenge, where temperature was raised at 0.2°C day-1 from their acclimation temperature (12°C) to mimic natural sea-cage farming conditions during the summer in Newfoundland. Interestingly, feed intake remained high up to 22°C, while previous studies have shown a decrease in salmon appetite after ∼16-18°C. After the first three mortalities were recorded at elevated temperature, a subset of LR and HR salmon were exposed to another acute handling stress event at 23.6°C. Basal and post-stress measurements of plasma cortisol, glucose and lactate did not differ between stress response phenotypes at this temperature. In the end, the average incremental thermal maximum (ITMax) of LR and HR fish was not different (25.1°C). In comparison, the critical thermal maximum (CTMax; temperature increased at 2°C h-1) of the remaining IR fish that had been held at 12°C was 28.5°C. Collectively, these results: 1) show that this population of Atlantic salmon is very thermally tolerant, and further question the relevance of CTMax in assessing responses to real-world temperature changes; and 2) indicate that characterization of stress phenotype at 9°C is not predictive of their stress response or survival at high temperatures. Therefore, selection of fish based on phenotypic stress response at low temperatures may not be beneficial to incorporate into Atlantic salmon breeding programs, especially if the goal is to improve growth performance and survival at high temperatures in sea-cages.

Npas4a expression in the teleost forebrain is associated with stress coping style differences in fear learning

Learning to anticipate potentially dangerous contexts is an adaptive behavioral response to coping with stressors. An animal’s stress coping style (e.g. proactive–reactive axis) is known to influence how it encodes salient events. However, the neural and molecular mechanisms underlying these stress coping style differences in learning are unknown. Further, while a number of neuroplasticity-related genes have been associated with alternative stress coping styles, it is unclear if these genes may bias the development of conditioned behavioral responses to stressful stimuli, and if so, which brain regions are involved. Here, we trained adult zebrafish to associate a naturally aversive olfactory cue with a given context. Next, we investigated if expression of two neural plasticity and neurotransmission-related genes (npas4a and gabbr1a) were associated with the contextual fear conditioning differences between proactive and reactive stress coping styles. Reactive zebrafish developed a stronger conditioned fear response and showed significantly higher npas4a expression in the medial and lateral zones of the dorsal telencephalon (Dm, Dl), and the supracommissural nucleus of the ventral telencephalon (Vs). Our findings suggest that the expression of activity-dependent genes like npas4a may be differentially expressed across several interconnected forebrain regions in response to fearful stimuli and promote biases in fear learning among different stress coping styles.

Differential effects of ethanol on behavior and GABAA receptor expression in adult zebrafish (Danio rerio) with alternative stress coping styles

Variation in stress responses between individuals are linked to factors ranging from stress coping styles to sensitivity of neurotransmitter systems. Many anxiolytic compounds (e.g. ethanol) can increase stressor engagement through modulation of neurotransmitter systems and are used to investigate stress response mechanisms. There are two alternative suites of correlated behavioral and physiological responses to stressors (stress coping styles) that differ in exploration tendencies: proactive and reactive stress coping styles. By chronically treating individuals differing in stress coping style with ethanol, a GABA-acting drug, we assessed the role of the GABAergic system on the behavioral stress response. Specifically, we investigated resulting changes in stress-related behavior (i.e. exploratory behavior) and whole-brain GABAA receptor subunits (gabra1, gabra2, gabrd, & gabrg2) in response to a novelty stressor. We found that ethanol-treated proactive individuals showed lower stress-related behaviors than their reactive counterparts. Proactive individuals showed significantly higher expression of gabra1, gabra2, and gabrg2 compared to reactive individuals and ethanol treatment resulted in upregulation of gabra1 and gabrg2 in both stress coping styles. These results suggest that impacts of ethanol on stress-related behaviors vary by stress coping style and that expression of select GABAA receptor subunits may be one of the underlying mechanisms.

Contextual fear learning and memory differ between stress coping styles in zebrafish

Animals frequently overcome stressors and the ability to learn and recall these salient experiences is essential to an individual’s survival. As part of an animal’s stress coping style, behavioral and physiological responses to stressors are often consistent across contexts and time. However, we are only beginning to understand how cognitive traits can be biased by different coping styles. Here we investigate learning and memory differences in zebrafish (Danio rerio) displaying proactive and reactive stress coping styles. We assessed learning rate and memory duration using an associative fear conditioning paradigm that trained zebrafish to associate a context with exposure to a natural olfactory alarm cue. Our results show that both proactive and reactive zebrafish learn and remember this fearful association. However, we note significant interaction effects between stress coping style and cognition. Zebrafish with the reactive stress coping style acquired the fear memory at a significantly faster rate than proactive fish. While both stress coping styles showed equal memory recall one day post-conditioning, reactive zebrafish showed significantly stronger recall of the conditioned context relative to proactive fish four days post-conditioning. Through understanding how stress coping strategies promote biases in processing salient information, we gain insight into mechanisms that can constrain adaptive behavioral responses.

Differences in stress and disease resilience related to emergence time for first feeding in farmed rainbow trout (Oncorhynchus mykiss).

Salmonid individuals show a relatively high variability in the time required to abandon the gravel nest where they hatch, the so-called 'emergence time'. Different behavioral and physiological traits have been shown to be associated with emergence time in wild salmonids. In general, early- and late-emerging fish have traits resembling those of proactive and reactive stress coping styles, respectively. Proactive fish are considered to be more resilient to stress and probably to disease, so it was hypothesized that fish with different emergence times have different abilities to resist repeated episodes of stress without suffering deleterious effects on their welfare or health status. In this study, rainbow trout eyed eggs were hatched and larvae were fractionated according to their emergence time (early fraction: first 20% of fish to emerge; intermediate fraction: mid 20%; late fraction: last 20%). When the fish were 4 months old, they were exposed to a daily repeated stress protocol for 15 days. The next day, both naïve and repeatedly stressed fish were exposed to an acute stress challenge. Different plasma (cortisol, glucose, lactate) as well as CNS (serotonergic activity) stress markers were assessed to evaluate the stress resilience of the different groups. Furthermore, an intraperitoneal infection challenge with Flavobacterium psychrophilum was carried out to assess disease resilience. Altogether, the results showed that fish from different fractions displayed differences in activation of the hypothalamus-pituitary-inter-renal axis, indicating a higher stress resilience in the fish with early emergence times. However, those differences were not reflected in the ability of the different fractions to grow and perform well in terms of growth, or in the ability to overcome infection with bacteria, which was similar for all the emergence fractions. This suggests that discriminating fish according to emergence time would probably have little effect in improving the performance and the welfare of farmed fish.

Emergence Time and Skin Melanin Spot Patterns Do Not Correlate with Growth Performance, Social Competitive Ability or Stress Response in Farmed Rainbow Trout.

In wild salmonid fish, specific individual behavioral traits have been correlated with the timing of fry emergence from their gravel spawning nests; Early emerging fish display more aggressive behavior and have a higher probability of becoming socially dominant, compared to fish that emerge at a later stage. Apart from aggression and dominance, other behavioral and metabolic traits, such as boldness, metabolic rate, or growth, have also been linked to emergence time. Altogether, the traits of early- and late-emerging fish resemble those of the proactive and reactive stress-coping style, respectively. As proactive fish are considered more resilient to stress, it may be desirable to select these for aquaculture production. However, it is currently unclear to what extent the link between emergence time and stress-coping styles is maintained in the selective breeding of farmed fish. In the present study, eyed eggs from a commercial supplier were hatched, and larvae fractionated according to their emergence time. Later on, juvenile fish from different emergence fractions were subjected to a stress challenge and also tested to evaluate their competitive ability for food. Beyond some slight dissimilarities in the acute stress responses, emergence fraction displayed no correlation with growth rates, or the ability to compete for feed. Within the whole group of fish utilized in the experiments, no relationship between skin melanin spot pattern and growth performance, stress response intensity, or competitive ability was found. Altogether, the differences in physiological traits related to emergence time were not as strong as those found in earlier studies. It is hypothesized, that the origin and degree of domestication of the fish might be partly responsible for this. The predictive value of skin spots or emergence time to infer the fish stress coping style in farmed fish is also discussed.

Predicting multifarious behavioural divergence in the wild

Many animals show complex behaviours that can have important ecological and evolutionary consequences. Environmental variation can lead to divergent selection that consistently favours particular behaviours in different environments; but how predictably multiple aspects of animal behaviour diverge in response to different environmental conditions remains unclear. We tested whether populations evolving under different levels of predation risk show predictable and repeatable population-level behavioural differences in all five primary components of animal personality: aggression, sociability, boldness, activity and exploration. We formulated and tested a priori predictions of divergence for each behaviour using the adaptive radiation of Bahamas mosquitofish, Gambusia hubbsi (family Poeciliidae), inhabiting vertical water-filled caves (blue holes) where they have evolved for thousands of years in either the presence or absence of predatory fish. Mosquitofish behaviours differed consistently, and largely predictably, between predation regimes: low-predation mosquitofish showed reduced sociability and greater exploration of a novel environment compared to high-predation counterparts. However, some differences were sex dependent: only females showed greater boldness and only males displayed reduced aggressiveness in low-predation populations. Activity levels did not differ between predation regimes. All populations showed a behavioural syndrome characteristic of either proactive or reactive stress-coping styles with regard to exploration. Exploration behavioural syndromes were more similar among populations that evolved in similar predation regimes, regardless of genetic relatedness. Using laboratory-born, high-predation mosquitofish, we confirmed that exploratory behaviours have a genetic basis and show significant within-individual repeatability. Our results suggest that environmental variation, such as chronic predation risk, can lead to repeatable, and often predictable, changes in multifarious animal behaviours, and that various aspects of behaviour can diversify more or less independently of one another. Considering the ecological importance of these behaviours, the ability to forecast behavioural shifts in a rapidly changing world could serve as a valuable conservation tool.

Correlated evolution of personality, morphology and performance

Evolutionary change in one trait can elicit evolutionary changes in other traits due to genetic correlations. This constrains the independent evolution of traits and can lead to unpredicted ecological and evolutionary outcomes. Animals might frequently exhibit genetic associations among behavioural and morphological-physiological traits, because the physiological mechanisms behind animal personality can have broad multitrait effects and because many selective agents influence the evolution of multiple types of traits. However, we currently know little about genetic correlations between animal personalities and nonbehavioural traits. We tested for associations between personality, morphology and locomotor performance by comparing zebrafish (Danio rerio) collected from the wild and then selectively bred for either a proactive or reactive stress coping style ('bold' or 'shy' phenotypes). Based on adaptive hypotheses of correlational selection in the wild, we predicted that artificial selection for boldness would produce correlated evolutionary responses of larger caudal regions and higher fast-start escape performance (and the opposite for shyness). After four to seven generations, morphology and locomotor performance differed between personality lines: bold zebrafish exhibited a larger caudal region and higher fast-start performance than fish in the shy line, matching predictions. Individual-level phenotypic correlations suggested that pleiotropy or physical gene linkage likely explained the correlated response of locomotor performance, while the correlated response of body shape may have reflected linkage disequilibrium, which is breaking down each generation in the laboratory. Our results indicate that evolution of personality can result in concomitant changes in morphology and whole-organism performance, and vice versa.

Differential responses to environmental challenge by common carp Cyprinus carpio highlight the importance of coping style in integrative physiology.

Common carp Cyprinus carpio displaying proactive or reactive stress coping styles were acclimated to two environmental regimes (low oxygen and low temperature), and selected groups were tested for response to an inflammatory challenge (Escherichia coli lipopolysaccharide, LPS). Plasma glucose and lactate levels were measured, as were selected C. carpio-specific messenger (m)RNA transcript abundance, including cortisol receptor (CR), enolase (ENO), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and interleukin-1-beta (IL1β) was measured in individual whole brain samples. Basal levels (in sham injected fish held in normoxic conditions at 25° C) of plasma lactate and glucose differed between coping styles, being significantly lower in proactive individuals. Both variables increased in response to LPS challenge, with the exception of plasma glucose in reactive fish held in hypoxia. Baseline levels of gene expression under control conditions were significantly different for GAPDH between behavioural phenotypes. The responses to experimental challenge were sometimes diametrically opposed between stress-coping styles in a transcript-specific manner. For CR and GAPDH, for example, the response to LPS injection in hypoxia were opposite between proactive and reactive animals. Proactive fish showed decreased CR and increased GAPDH, whereas reactive showed the opposite response. These results further highlight that screening for stress-coping styles prior to experiments in adaptive physiology can significantly affect the interpretation of data obtained. Further, this leads to a more finely tuned analytical output providing an improved understanding of variation in individual responses to both environmental and inflammatory challenge.

Characterizing the neurotranscriptomic states in alternative stress coping styles.

BackgroundAnimals experience stress in many contexts and often successfully cope. Individuals exhibiting the proactive versus reactive stress coping styles display qualitatively different behavioral and neuroendocrine responses to stressors. The predisposition to exhibiting a particular coping style is due to genetic and environmental factors. In this study we explore the neurotranscriptomic and gene network biases that are associated with differences between zebrafish (Danio rerio) lines selected for proactive and reactive coping styles and reared in a common garden environment.ResultsUsing RNA-sequencing we quantified the basal transcriptomes from the brains of wild-derived zebrafish lines selectively bred to exhibit the proactive or reactive stress coping style. We identified 1953 genes that differed in baseline gene expression levels. Weighted gene coexpression network analyses identified one gene module associated with line differences. Together with our previous pharmacological experiment, we identified a core set of 62 genes associated with line differences. Gene ontology analyses reveal that many of these core genes are implicated in neurometabolism (e.g. organic acid biosynthetic and fatty acid metabolic processes).ConclusionsOur results show that proactive and reactive stress coping individuals display distinct basal neurotranscriptomic states. Differences in baseline expression of select genes or regulation of specific gene modules are linked to the magnitude of the behavioral response and the display of a coping style, respectively. Our results expand the molecular mechanisms of stress coping from one focused on the neurotransmitter systems to a more complex system that involves an organism’s capability to handle neurometabolic loads and allows for comparisons with other animal taxa to uncover potential conserved mechanisms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1626-x) contains supplementary material, which is available to authorized users.

Coupling between stress coping style and time of emergence from spawning nests in salmonid fishes: Evidence from selected rainbow trout strains (Oncorhynchus mykiss)

Correlations between behavioral and physiological traits, often referred to as stress coping styles, have been demonstrated in numerous animal groups. Such trait variations often cluster in two contrasting styles, with animals characterized as either proactive or reactive. In natural populations of salmonid fishes, emergence from spawning nests, when fry establish a territory and shifts from exogenous to endogenous feeding, is a crucial niche shift with a high selection pressure. The timing of this event is correlated to behavioral and physiological traits such as aggression, boldness/shyness, dominance, and metabolic rate; resembling those of proactive and reactive stress coping styles. In farmed fish populations, however the relation between emergence and stress coping styles seems to be absent, an effect which has been related to lack of selection pressure during emergence. In the present study two rainbow trout strains genetically selected as LR (low-responsive) and HR (high-responsive) trout, characterized with proactive (LR) and reactive (HR) stress coping traits, was used to further investigate the relationship between the time of emergence and stress coping style in salmonid fishes. For this task LR and HR larvae were hatched in mixed batches, and thirty individuals from the earliest and latest 25% of emerging larvae were randomly collected. Thereafter, a line specific genetic marker was used to distinguish the proportion of LR and HR occurring in early and late fractions. The result demonstrates a higher proportion of LR fry in the early fraction in comparison to the HR fry, which emerged at a higher proportion during the late period. Early emerging individuals had larger yolk reserves at emergence, lending further support to a relationship between emergence times, yolk reserves at emergence and stress coping styles in salmonids. Smaller larval bodies in early compared to late emerging individuals suggest that this difference in yolk size reflects differences in developmental stages at emergence. These data suggests that a genetic link between emergence time and stress coping style persists in captive salmonid fishes.

Effects of maternal stress coping style on offspring characteristics in rainbow trout (Oncorhynchus mykiss)

Maternal size, age, and allostatic load influence offspring size, development, and survival. Some of these effects have been attributed to the release of glucocorticoids, and individual variation in these stress hormones is related to a number of traits. Correlated traits are often clustered and used to define the proactive and reactive stress coping styles. Although stress coping styles have been identified in a number of animal groups, little is known about the coupling between stress coping style and offspring characteristics. In the present study, plasma cortisol levels in ovulated mothers and cortisol levels in non-fertilized eggs from two rainbow trout (Oncorhynchus mykiss) strains selected for high (HR) and low (LR) post-stress plasma cortisol levels were compared. Offspring characteristics such as egg size, larval growth, and energy reserves also were compared between the two strains. Maternal plasma and egg cortisol levels were correlated, but no difference between the HR and LR strains was detected in either parameter. LR females produced larger eggs, and larvae with larger yolk sacs compared to HR females, however no differences in larval body size (excluding the yolk) was detected between strains. Considering that the HR and LR strains have a number of correlated behavioral and physiological traits that resemble the reactive and proactive stress coping styles, respectively, the results suggest that proactive mothers invest more energy into their offspring, producing larvae with larger energy reserves. It is possible that larger energy reserves in proactive larvae support the energy requirement for establishing and defending territory in salmonid fish. Furthermore, in the present study we found a positive relationship between mother plasma cortisol and egg cortisol; however neither mother plasma cortisol nor egg cortisol differed between strains. These results indicate that cortisol endowment from the mother to the offspring plays a minor role in the transfer of the behavioral and physiological traits which separates these strains.

Consistent boldness behaviour in early emerging fry of domesticated Atlantic salmon (Salmo salar): Decoupling of behavioural and physiological traits of the proactive stress coping style

Individual variation in the way animals cope with stressors has been documented in a number of animal groups. In general, two distinct sets of behavioural and physiological responses to stress have been described: the proactive and the reactive coping styles. Some characteristics of stress coping style seem to be coupled to the time to emerge of fry from spawning redds in natural populations of salmonid fishes. In the present study, behavioural and physiological traits of stress coping styles were compared two and five months after emergence in farmed Atlantic salmon (Salmo salar), using individuals with an early or late time to emerge. Initially, compared to late emerging individuals, early emerging individuals showed a shorter time to resume feeding after transfer to rearing in isolation. Resumption of feeding after isolation was suggested to be related to boldness behaviour, rather than hunger, in the present study. This observation was repeated five months after emergence, demonstrating behavioural consistency over time in this trait. However, in other traits of proactive and reactive stress coping styles, such as social status, resting metabolism or post stress cortisol concentrations, early and late emerging individuals did not differ. Therefore, this study demonstrates that boldness in a novel environment is uncoupled from other traits of the proactive and reactive stress coping styles in farmed salmonids. It is possible that this decoupling is caused by the low competitive environment in which fish were reared. In natural populations of salmonids, however, the higher selection pressure at emergence could select for early emerging individuals with a proactive coping style.

Response to environmental change in rainbow trout selected for divergent stress coping styles

An extensive literature has documented differences in the way individual animals cope with environmental challenges and stressors. Two broad patterns of individual variability in behavioural and physiological stress responses are described as the proactive and reactive stress coping styles. In addition to variability in the stress response, contrasting coping styles may encompass a general difference in behavioural flexibility as opposed to routine formation in response to more subtle environmental changes and non-threatening novelties. In the present study two different manipulations, relocating food from a previously learned location, and introducing a novel object yielded contrasting responses in rainbow trout selected for high (HR) and low (LR) post stress plasma cortisol levels. No difference was seen in the rate of learning the original food location; however, proactive LR fish were markedly slower than reactive HR fish in altering their food seeking behaviour in response to relocated food. In contrast, LR fish largely ignored a novel object which disrupted feeding in HR fish. Hence, it appears that the two lines appraise environmental cues differently. This observation suggests that differences in responsiveness to environmental change are an integral component of heritable stress coping styles, which in this particular case, had opposite effects on foraging efficiency in different situations. Context dependent fitness effects may thus explain the persistence of stable divergence of this evolutionary widespread trait complex.