Behavioral variation shows heritability in juvenile brown trout Salmo trutta

Effects of Cheliped Amputation on the Personality of Crayfish

Animal personality, which describes inter-individual differences and intra-individual consistency in behaviors across time and contexts, has been widely observed and has significance for both ecology and evolution. Morphological modifications, particularly during early life stages, may highly influence animal behavior in adulthood; thus, exploring this relationship can elucidate personality development throughout ontogeny. In this study, we reared juvenile crayfish (Procambarus clarkii) with different degrees of cheliped mutilation and explored their personality patterns, including exploration and aggression, when they reached sexual maturity. Male crayfish showed repeatability in exploration, and both sexes showed repeatability in aggression. We observed no significant correlation between the two behavioral traits, indicating the absence of behavioral syndromes. Moreover, exploration did not differ according to the type of mutilation, but crayfish with more intact chelipeds were more aggressive, and males were more aggressive than females. These results indicate that cheliped mutilation may modify the average levels of personality traits associated with competition or self-defense. Our study provides insights into how morphological modifications may shape animal personalities in adulthood.

Interpopulation variation of behavioural and morphological traits that affect downstream displacement of the juvenile white-spotted charr Salvelinus leucomaenis

Downstream displacement, the passive downstream dispersal of riverine organisms, can generate evolutionary pressures that selectively remove susceptible individuals from upstream habitats. These evolutionary pressures may accumulate over time in fish populations situated upstream of a tall check dam that displaced fish are unable to swim over and can be diluted by the homing of displaced individuals in the absence of such barriers. Here, we conducted interpopulation comparisons between above-dam and unrestricted open-stream populations of the juvenile white-spotted charr Salvelinus leucomaenis to test the hypothesis that above-dam juveniles possess more advantageous traits that reduce downstream displacement than open-stream juveniles. We focused on sedentary behaviour and body depth, both of which are known to affect downstream displacement. Interpopulation comparisons revealed that juveniles from above-dam populations were consistently more sedentary than those from open-stream populations. On the other hand, there were no systematic differences in body depth between above-dam and open-stream populations. These results are consistent with the evolution of behaviours in above-dam populations that inhibit downstream displacement. However, several other factors could explain the results obtained and further studies will be needed to confirm the presence of behavioural evolution in our study system.

The consistency of exploration behaviours across life stages in a native Australian rodent, the fawn-footed mosaic-tailed rat Melomys cervinipes

Many species show inter-individual variation in exploratory behaviours that are consistent over time, reflecting a personality. Differences in exploration can affect how individuals acquire resources and use their environment. However, few studies have considered whether exploratory behaviours are consistent across developmental life stages, such as when individuals disperse out the natal territory or when they become sexually mature. We therefore investigated the consistency of exploration behaviours towards a novel object and novel environment in a native Australian rodent, the fawn-footed mosaic-tailed rat Melomys cervinipes across development. Individuals were tested in an open field test and novel object test for five trials across four different life stages (pre-weaning, recently weaned, independent juvenile, sexually mature adult). We found that individual mosaic-tailed rats were consistent in their exploration of novel objects over these life stages, as these behaviours were repeatable and did not change across testing replicates. However, how individuals explored novel environments was not repeatable and changed across development, with exploration peaking during the independent juvenile stage. These results suggest that the way an individual interacts with novel objects may be somewhat constrained by genetic or epigenetic effects early in development, whereas spatial exploration could be more flexible to facilitate developmental shifts, such as dispersal. The life stage of an animal should therefore be taken into consideration when assessing personality in different species.

Individual variation, personality, and the ability of animals to cope with climate change

The Sixth Assessment of the Intergovernmental Panel on Climate Change describes negative effects of climate change on animals occurring on a larger scale than previously appreciated. Animal species are increasingly experiencing more frequent and extreme weather in comparison with conditions in which the species evolved. Individual variation in behavioural and physiological responses of animals to stimuli from the environment is ubiquitous across all species. Populations with relatively high levels of individual variation are more likely to be able to survive in a range of environmental conditions and cope with climate change than populations with low levels of variation. Behavioural and physiological responses are linked in animals, and personality can be defined as consistent individual behavioural and physiological responses of animals to changes in their immediate environment. Glucocorticoids (cortisol and corticosterone) are hormones that, in addition to metabolic roles, are released when the neuroendocrine stress system is activated in response to stimuli from the environment perceived to be threatening. The size of a glucocorticoid response of an animal is an indication of the animal’s personality. Animals with reactive personalities have relatively high glucocorticoid responses, are relatively slow and thorough to explore new situations, and are more flexible and able to cope with changing or unpredictable conditions than animals with proactive personalities. Animals with reactive personalities are likely to be better able to cope with environmental changes due to climate change than animals with proactive personalities. A reaction norm shows the relationship between phenotype and environmental conditions, with the slope of a reaction norm for an individual animal a measure of phenotypic plasticity. If reaction norm slopes are not parallel, there is individual variation in plasticity. Populations with relatively high individual variation in plasticity of reaction norms will have more animals that can adjust to a new situation than populations with little variation in plasticity, so are more likely to persist as environments change due to climate change. Future studies of individual variation in plasticity of responses to changing environments will help understanding of how populations of animals may be able to cope with climate change.

Selecting aggressiveness to improve biological control agents efficiency

In agroecosystems, omnivorous predators are recognized as potential biological control agents because of the numerous pest species they prey on. Nonetheless, it could be possible to enhance their efficiency through artificial selection on traits of economical or ecological relevance. Aggressiveness, which defines the readiness of an individual to display agonistic actions toward other individuals, is expected to be related to zoophagy, diet preferences and to a higher attack rate. The study aimed to assess the aggressiveness degree of the damsel bug, Nabis americoferus, and to estimate its heritability. We hypothesized that a high aggressiveness degree can be selected, and that males are more aggressive than females. Using artificial selection, we reared two separate populations, each composed of nine genetically isolated lines characterized by their different aggressiveness degree (aggressive, docile and non-selected). After three generations, we had efficiently selected aggressive behavior. The realized heritability was 0.16 and 0.27 for aggressiveness and docility in the first population. It was 0.25 and 0.23 for the second population. Males were more aggressive than females only for the second population. The potential of these individuals as biological control agents and the ecological consequences of aggressiveness are discussed.

Technical suitability and reliability of an in vivo and non-invasive biosensor-type glucose assessment as a potential biomarker for multiple stressors in fishes: an evaluation on Salmonids

Regardless of the wide use of glucose measurements in stress evaluation, there are some inconsistencies in its acceptance as a stress marker. To meet the challenge and test the reliability/suitability of glucose measurement in practice, we simulated different environmental/anthropogenic exposure scenarios in this study. We aimed to provoke stress in fish followed by a 2-week stress recovery period and under the cumulative effect of leachate fish exposed to pathogenic oomycetes (Saprolegnia parasitica) to represent a possible infection in fish. We selected stream-resident and anadromous brown trout ecotypes (Salmo trutta) representing salmonids with different migratory behaviour strategies. Here, we analysed glucose content in fish-holding water, blood and gills to determine glucose suitability as a potential biomarker of fish response to environmental challenges. Additionally, swimming behavioural parameters and haematocrit were measured. The results indicated that the quantity of glucose released in the holding water of stressed fish increased considerably and remained substantially higher throughout the stress recovery period than the control level. Correspondingly, the circulating levels of glucose in blood and gills decreased over time in fish exposed to different stressors. A significant decrease in swimming activity of fish was observed during the first hours of leachate exposure and increased in fish exposed to S. parasitica compared to control. Our study is the first to ensure the validity and reliability of glucose response in evaluating physiological stress in fish under chemical and biological stimuli, indicating its sensitivity and response range of glucose measurement in fish-holding water.

Selection on fish personality differs between a no-take marine reserve and fished areas

Marine reserves can protect fish populations by increasing abundance and body size, but less is known about the effect of protection on fish behaviour. We looked for individual consistency in movement behaviours of sea trout in the marine habitat using acoustic telemetry to investigate whether they represent personality traits and if so, do they affect survival in relation to protection offered by a marine reserve. Home range size had a repeatability of 0.21, suggesting that it represents a personality trait, while mean swimming depth, activity and diurnal vertical migration were not repeatable movement behaviours. The effect of home range size on survival differed depending on the proportion of time fish spent in the reserve, where individuals spending more time in the reserve experienced a decrease in survival with larger home ranges while individuals spending little time in the reserve experienced an increase in survival with larger home ranges. We suggest that the diversity of fish home range sizes could be preserved by establishing networks of marine reserves encompassing different habitat types, ensuring both a heterogeneity in environmental conditions and fishing pressure.

Fluoxetine results in misleading conclusions on fish behavior

Fluoxetine is an antidepressant medicine causing relaxation and mood improvement in people, with silencing certain personality traits in some cases. The question arise if such phenomena can be observed in nontarget organisms such as fish. Fluoxetine affects fishes behavior; however, it is not known if the medicine affects its "personality." This study aimed to evaluate the reaction of the invasive Neogobius fluviatilis and native Gobio gobio individuals to fluoxetine at environmental concentration of 360 ng/L. We prepared three variants of the experiments: (a) behavioral trials with unexposed fishes, (b) behavioral trials with the same fishes after 21 days of fluoxetine exposure, and (c) behavioral trials with the same fishes after 21-day depuration period, that is, without fluoxetine. The fishes reaction time (RT), that is, difference in time spent on reaching food with and without the necessity of overcoming the obstacle, was analyzed. Additionally, the personality, bold or shy, traits of each fish individual, was assigned. The results indicated that environmental concentrations of the antidepressant influenced RT. The average RT of the fishes cultured with fluoxetine was by 7-min shorter in comparison with the nonexposed control. Share of individuals exposed to fluoxetine assigned as bold raised to 71.4% in comparison with 46.4% in nonexposed control. This sheds new light on wild fishes behavior caught from freshwater. Environmental concentrations of the antidepressant influenced the time of fishes reaction and share individuals assigned as bold. Moreover, 21-day recovery lasting might be not enough to get fluoxetine effect on fishes.

Does parental angling selection affect the behavior or metabolism of brown trout parr?

The behavior of organisms can be subject to human-induced selection such as that arising from fishing. Angling is expected to induce mortality on fish with bold and explorative behavior, which are behaviors commonly linked to a high standard metabolic rate. We studied the transgenerational response of brown trout (Salmo trutta) to angling-induced selection by examining the behavior and metabolism of 1-year-old parr between parents that were or were not captured by experimental fly fishing. We performed the angling selection experiment on both a wild and a captive population, and compared the offspring for standard metabolic rate and behavior under predation risk in common garden conditions. Angling had population-specific effects on risk taking and exploration tendency, but no effects on standard metabolic rate. Our study adds to the evidence that angling can induce transgenerational responses on fish personality. However, understanding the mechanisms of divergent responses between the populations requires further study on the selectivity of angling in various conditions.

Examining the effects of chronic, lake-wide elevated temperatures on behavioural expression in largemouth bass, Micropterus salmoides

Many behaviours have differential fitness consequences across thermal and ecological contexts, indicating that both ecological shifts and warming temperatures induced by climatic change may alter how organisms behave. However, empirical evidence of temperature-driven behavioural selection in natural systems is lacking. We compared behaviours and behavioural syndromes related to activity, exploration, boldness and aggression in populations of largemouth bass (Micropterus salmoides) from ambient lakes to the those from artificially warmed, power plant cooling lakes to investigate changes in behaviours associated with warmer environments. Activity, exploration, boldness and aggression of juvenile largemouth bass were assessed in laboratory conditions using a novel environment assay and a risky situation assay. We found that activity and exploratory behaviours were higher and decreased through first year ontogeny in populations from heated lakes, whereas these behaviours were lower and showed no relationship through ontogeny in populations from ambient lakes. We attribute these differences to the changes in food source availability in heated lakes associated with temperature-driven ecological effects. Bold and aggressive behaviours tended to differ between populations, as did correlations between behaviours, but did not differ between ambient and heated lakes. The findings of this work identify that large ecological changes associated with warming environments, such as food availability, may drive changes in some aspects of behavioural expression in largemouth bass but that other aspects of behavioural expression may be driven by lake-specific factors not related to warming.

Sperm cryopreservation reduces offspring growth

Sperm cryopreservation is routinely used in reproductive medicine, livestock production and wildlife management. Its effect on offspring performance is often assumed to be negligible, but this still remains to be confirmed in well-controlled within-subject experiments. We use a vertebrate model that allows us to experimentally separate parental and environmental effects to test whether sperm cryopreservation influences offspring phenotype under stress and non-stress conditions, and whether such effects are male-specific. Wild brown trout (Salmo trutta) were stripped for their gametes, and a portion of each male's milt was cryopreserved. Then, 960 eggs were simultaneously fertilized with either non-cryopreserved or frozen-thawed semen and raised singly in the presence or absence of a pathogen. We found no significant effects of cryopreservation on fertilization rates, and no effects on growth, survival nor pathogen resistance during the embryo stage. However, fertilization by cryopreserved sperm led to significantly reduced larval growth after hatching. Males varied in genetic quality as determined from offspring performance, but effects of cryopreservation on larval growth were not male-specific. We conclude that cryopreservation causes a reduction in offspring growth that is easily overlooked because it only manifests itself at later developmental stages, when many other factors affect growth and survival too.

Food deprived largemouth bass (Micropterus salmoides) are inactive and stressed, but do not show changes in lure inspections

Coping style traits, including physiology and behavior, can be used to predict if fish are vulnerable to capture by hook-and-line angling. Typically, fish with proactive coping styles are selectively captured, but effects of environmental influences, such as food availability, on the completion of each step leading to a successful angling capture (i.e., activity rates, encountering a lure, lure inspection, lure-striking, and ingestion) have not been quantified. Therefore, the objective of this study was to quantify the effects among activity behavior, stress (cortisol) responsiveness, and food availability on lure inspection behaviors of largemouth bass. No relationships were found between activity, stress responsiveness, and food availability to determine lure inspections. However, food deprivation decreased activity rates and increased baseline cortisol concentrations of largemouth bass. Additionally, after feeding treatments, fish with low baseline cortisol concentrations were more likely to inspect lures in both the fed and food deprived treatments. Results further discuss the implications of study findings to help fisheries managers predict the evolutionary impacts of angling.

Experimental crossbreeding reveals strain-specific variation in mortality, growth and personality in the brown trout (Salmo trutta)

Although hybridization between populations with low genetic diversity may induce heterosis, it can also lead to reduced fitness of hybrid offspring through outbreeding depression and loss of local adaptations. Using a half-sib mating design, we studied on brown trout (Salmo trutta) how hybridization of migratory hatchery-strain females with males from various strains would affect early mortality, growth and personality in F₁ offspring. No differences in mortality or alevin body length were found between the crossing groups by the end of the yolk-sac stage. At later developmental stages, higher mortality and slower growth in one of the geographically distant hybrid groups indicated potential outbreeding depression. The personality component indicating boldness and exploration tendency showed fairly low genetic variation and no phenotypic differences among the crossing groups while the personality component related to freezing behavior indicated stronger freezing responses in the purebred and local cross strain when compared to the two other strains. However, the purebred hatchery strain possessed stronger additive genetic tendency for boldness and explorative behavior, and weaker genetic tendency for freezing behavior, when compared to the wild × hatchery hybrid group. Our results add to the cumulating evidence of risks related to the stocking of fish strains from non-native origins.

Do Metabolic Traits, Vulnerability to Angling, or Capture Method Explain Boldness Variation in Eurasian Perch?

The pace-of-life syndrome (POLS) concept predicts that individuals with high baseline metabolic rates demonstrate high boldness, aggressiveness, and activity, especially in food acquisition, with associated relatively greater energy requirements. In fishes, these behaviors may increase individual vulnerability to angling. To test the predictions of the POLS concept, we quantified individual standard metabolic rate (SMR) and boldness in both wild-caught and hatchery-reared Eurasian perch (Perca fluviatilis). We found both SMR and boldness to be repeatable traits but detected no correlation between them. Individual vulnerability to angling was assessed in the hatchery-reared perch, but we found no difference in boldness or SMR between vulnerable and nonvulnerable perch. Wild-caught perch were ice fished using either natural or artificial bait, and we observed no differences in boldness or SMR with respect to bait type or capture order. Our findings do not support the predictions of the POLS concept and, consistent with earlier studies in perch, suggest that angling may not drive selection against boldness in this species.

Linking organismal growth, coping styles, stress reactivity, and metabolism via responses against a selective serotonin reuptake inhibitor in an insect

Evidence suggests that brain serotonin (5-HT) is one of the central mediators of different types of animal personality. We tested this assumption in field crickets Gryllus integer using a selective serotonin reuptake inhibitor (SSRI). Crickets were selected for slow and rapid development and tested for their coping styles under non-stressful conditions (time spent exploring a novel object). Resting metabolic rate, maximum metabolic rate and latency to resume activity were measured under stressful conditions (stress reactivity). Measurements were taken (i) before and (ii) during the SSRI treatment. Before the SSRI treatment, a strong negative correlation was observed between coping style and stress reactivity, which suggests the existence of a behavioral syndrome. After the SSRI treatment, the syndrome was no longer evident. The results of this study show that 5-HT may be involved in regulating behavior not only along a stress reactivity gradient but also along a coping styles axis. The relationship between personality and the strength and direction of 5-HT treatment on observed behaviors indicates trait-like individual differences in 5-HT signaling. Overall, these findings do not support recent ideas arising from the pace-of-life syndrome (POLS) hypothesis, which predict higher exploration and metabolic rates in rapidly developing bold animals.

A physiological perspective on fisheries-induced evolution

There is increasing evidence that intense fishing pressure is not only depleting fish stocks but also causing evolutionary changes to fish populations. In particular, body size and fecundity in wild fish populations may be altered in response to the high and often size‐selective mortality exerted by fisheries. While these effects can have serious consequences for the viability of fish populations, there are also a range of traits not directly related to body size which could also affect susceptibility to capture by fishing gears—and therefore fisheries‐induced evolution (FIE)—but which have to date been ignored. For example, overlooked within the context of FIE is the likelihood that variation in physiological traits could make some individuals within species more vulnerable to capture. Specifically, traits related to energy balance (e.g., metabolic rate), swimming performance (e.g., aerobic scope), neuroendocrinology (e.g., stress responsiveness) and sensory physiology (e.g., visual acuity) are especially likely to influence vulnerability to capture through a variety of mechanisms. Selection on these traits could produce major shifts in the physiological traits within populations in response to fishing pressure that are yet to be considered but which could influence population resource requirements, resilience, species’ distributions and responses to environmental change.

Maternal effects in vulnerability to eye-parasites and correlations between behavior and parasitism in juvenile Arctic charr

Hatchery‐reared fish show high mortalities after release to the wild environment. Explanations for this include potentially predetermined genetics, behavioral, and physiological acclimation to fish farm environments, and increased vulnerability to predation and parasitism in the wild. We studied vulnerability to Diplostomum spp. parasites (load of eye flukes in the lenses), immune defense (relative spleen size) and antipredator behaviors (approaches toward predator odor, freezing, and swimming activity) in hatchery‐reared juvenile Arctic charr (Salvelinus alpinus) using a nested mating design. Fish were exposed to eye‐fluke larvae via the incoming water at the hatchery. Fish size was positively associated with parasite load, but we did not find any relationship between relative spleen size and parasitism. The offspring of different females showed significant variation in their parasite load within sires, implying a dam effect in the vulnerability to parasites. However, the family background did not have any effect on spleen size. In the mean sire level over dams, the fish from the bolder (actively swimming) families in the predator trials suffered higher loads of eye flukes than those from more cautiously behaving families. Thus, the results indicate potentially maternally inherited differences in vulnerability to eye‐fluke parasites, and that the vulnerability to parasites and behavioral activity are positively associated with each other at the sire level. This could lead to artificial and unintentional selection for increased vulnerability to both parasitism and predation if these traits are favored in fish farm environments.

Hormonal responsiveness to stress is negatively associated with vulnerability to angling capture in fish

Differences in behavior and physiology amongst individuals often alter relative fitness levels in the environment. However, the ideal behavioral/physiological phenotype in a given environment may be altered by human activity, leading to an evolutionary response in the affected population. One example of this process can be found in fisheries (including recreational freshwater fisheries), where selective capture and harvest of individuals with certain phenotypes can drive evolutionary change. While some life history traits and behavioral tendencies influencing capture likelihood have been studied, the physiological mechanisms driving this vulnerability remain poorly understood. To address this, we assessed how two major physiological characteristics (hormonal responsiveness to stress and metabolic phenotype) and one behavioral characteristic (boldness) impact the likelihood of an individual being captured by anglers. Largemouth bass, Micropterus salmoides, derived from a population artificially selected for differential angling vulnerability were assessed for boldness and for stress responsiveness (as indicated by plasma cortisol levels) following an air-exposure challenge. Largemouth bass were then stocked into a pond where experimental angling trials took place, and a subset of captured and uncaptured fish were afterwards assessed for metabolic phenotype. The results showed that stress responsiveness was the primary driver of angling vulnerability, with individuals that experienced lower rises in cortisol following the air-exposure challenge more likely to be captured. Neither boldness nor metabolic phenotype influenced capture probability. The results from this study indicate that fisheries-induced selective pressure may act on physiology, potentially altering stress responsiveness and its associated behaviors in populations exploited by recreational anglers.

To be so bold: boldness is repeatable and related to within individual behavioural variability in North Island robins

Behavioural research traditionally focusses on the mean responses of a group of individuals rather than variation in behaviour around the mean or among individuals. However, examining the variation in behaviour among and within individuals may also yield important insights into the evolution and maintenance of behaviour. Repeatability is the most commonly used measure of variability among individuals in behavioural research. However, there are other forms of variation within populations that have received less attention. One such measure is intraindividual variation in behaviour (IIV), which is a short-term fluctuation of within-individual behaviour. Such variation in behaviour might be important during interactions because it could decrease the ability of conspecific and heterospecific individuals to predict the behaviour of the subject, thus increasing the cost of the interaction. In this experiment, we made repeated measures of the latency of North Island robins to attack a prey in a novel situation (a form of boldness) and examined (i) repeatability of boldness (the propensity to take a risk), (ii) IIV of boldness, and (iii) whether there was a significant relationship between these two traits (a behavioural syndrome). We found that boldness was highly repeatable, that there were high levels of IIV in boldness, and that there was a negative relationship between boldness and IIV in boldness. This suggests that despite high levels of repeatability for this behaviour, there were also still significant differences in IIV among different individuals within the population. Moreover, bolder individuals had significantly less IIV in their boldness, which suggests that they were forming routines (which reduces behavioural variability) compared to shyer individuals. Our results definitively demonstrate that IIV itself varies across individuals and is linked with key behavioural traits, and we argue for the importance of future studies aimed at understanding its causes and consequences for behavioural interactions.

Brain cortisol receptor expression differs in Arctic charr displaying opposite coping styles

Individually consistent behavioral and physiological responses to stressful situations (often referred to as coping styles) has been reported in many animal species. Differences in hypothalamic-pituitary axis reactivity characterize individuals, and it has been proposed that the glucocorticoid (gr) and mineralocorticoid (mr) receptors are fundamental in regulating coping styles. We sorted individuals into reactive and proactive coping styles by collapsing behavioral outputs from net restraint and confinement stress tests in a principal component analysis. We then analyzed plasma cortisol levels, serotonin neurochemistry and the relative mRNA expression of gr1 and mr in stressed individuals per coping style. Proactive fish were characterized as having a lower serotonergic activity and being more active under stress. In addition, proactive fish had higher hypothalamic gr1 and mr abundance and a higher mr/gr1 ratio, compared to reactive fish. We found no significant differences in cortisol or telencephalic mRNA, gr1 and mr expression, or their ratio. Brain MR and GR have been proven to have an important role in the appraisal, coping and adaptation to stressful stimuli, so that a higher expression of these receptors in proactive fish suggests increased tolerance and performance under stress, compared to reactive individuals. We present evidence of a conserved neuroendocrine mechanism associated with coping styles in a fish species which is ecologically very diverse and considered to be the most cold-adapted fish in freshwater. We propose that this may be a first step into exploiting this model in order to better understand climate-change related effects in sub populations and ecophenotypes.

Heritability of Boldness and Hypoxia Avoidance in European Seabass, Dicentrarchus labrax

To understand the genetic basis of coping style in European seabass, fish from a full factorial mating (10 females x 50 males) were reared in common garden and individually tagged. Individuals coping style was characterized through behavior tests at four different ages, categorizing fish into proactive or reactive: a hypoxia avoidance test (at 255 days post hatching, dph) and 3 risk-taking tests (at 276, 286 and 304 dph). We observed significant heritability of the coping style, higher for the average of risk-taking scores (h² = 0.45 ± 0.14) than for the hypoxia avoidance test (h² = 0.19 ± 0.10). The genetic correlations between the three risk-taking scores were very high (r_A = 0.96–0.99) showing that although their repeatability was moderately high (r_P = 0.64–0.72), successive risk-taking tests evaluated the same genetic variation. A mild genetic correlation between the results of the hypoxia avoidance test and the average of risk-taking scores (0.45 ± 0.27) suggested that hypoxia avoidance and risk-taking tests do not address exactly the same behavioral and physiological responses. Genetic correlations between weight and risk taking traits showed negative values whatever the test used in our population i.e. reactive individual weights were larger. The results of this quantitative genetic analysis suggest a potential for the development of selection programs based on coping styles that could increase seabass welfare without altering growth performances. Overall, it also contributes to a better understanding of the origin and the significance of individual behavioral differences.

Characterization of stress coping style in Senegalese sole (Solea senegalensis) juveniles and breeders for aquaculture

The aim of this work was to characterize stress coping styles of Senegalese sole (Solea senegalensis) juveniles and breeders and to select an operational behavioural screening test (OBST) that can be used by the aquaculture industry to classify and select between behavioural phenotypes in order to improve production indicators. A total of 61 juveniles and 59 breeders were subjected to five individual behavioural tests and two grouping tests. At the end of the individual tests, all animals were blood sampled in order to measure cortisol, glucose and lactate. Three tests (restraining, new environment and confinement) characterized the stress coping style behaviour of Senegalese sole juveniles and breeders and demonstrated inter-individual consistency. Further, the tests when incorporated into a principal components analysis (PCA) (i) identified two principal axes of personality traits: 'fearfulness-reactivity' and 'activity-exploration', (ii) were representative of the physiological axis of stress coping style, and (iii) were validated by established group tests. This study proposed for the first time three individual coping style tests that reliably represented proactive and reactive personalities of Senegalese sole juveniles and breeders. In addition, the three proposed tests met some basic operational criteria (rapid testing, no special equipment and easy to apply and interpret) that could prove attractive for fish farmers to identify fish with a specific behaviour that gives advantages in the culture system and that could be used to establish selection-based breeding programmes to improve domestication and production.

State-dependent behavior and alternative behavioral strategies in brown trout (Salmo trutta L.) fry

ABSTRACT

Animals generally adjust their behavior in response to bodily state (e.g., size and energy reserves) to optimize energy intake in relation to mortality risk, weighing predation probability against the risk of starvation. Here, we investigated whether brown trout Salmo trutta adjust their behavior in relation to energetic status and body size during a major early-life selection bottleneck, when fast growth is important. Over two consecutive time periods (P1 and P2; 12 and 23 days, respectively), food availability was manipulated, using four different combinations of high (H) and low (L) rations (i.e., HH, HL, LH, and LL; first and second letter denoting ration during P1 and P2, respectively). Social effects were excluded through individual isolation. Following the treatment periods, fish in the HL treatment were on average 15-21 % more active than the other groups in a forced open-field test, but large within-treatment variation provided only weak statistical support for this effect. Furthermore, fish on L-ration during P2 tended to be more actively aggressive towards their mirror image than fish on H-ration. Body size was related to behavioral expression, with larger fish being more active and aggressive. Swimming activity and active aggression were positively correlated, forming a behavioral syndrome in the studied population. Based on these behavioral traits, we could also distinguish two behavioral clusters: one consisting of more active and aggressive individuals and the other consisting of less active and aggressive individuals. This indicates that brown trout fry adopt distinct behavioral strategies early in life.

SIGNIFICANCE STATEMENT

This paper provides information on the state-dependence of behavior in animals, in particular young brown trout. On the one hand, our data suggest a weak energetic state feedback where activity and aggression is increased as a response to short term food restriction. This suggests a limited scope for behavioral alterations in the face of starvation. On the other hand, body size is linked to higher activity and aggression, likely as a positive feedback between size and dominance. The experiment was carried out during the main population survival bottleneck, and the results indicate that growth is important during this stage, as 1) behavioral compensation to increase growth is limited, and 2) growth likely increases the competitive ability. However, our data also suggests that the population separates into two clusters, based on combined scores of activity and aggression (which are positively linked within individuals). Thus, apart from an active and aggressive strategy, there seems to be another more passive behavioral strategy.

Does boldness explain vulnerability to angling in Eurasian perch Perca fluviatilis?

Consistent individual differences (CIDs) in behavior are of interest to both basic and applied research, because any selection acting on them could induce evolution of animal behavior. It has been suggested that CIDs in the behavior of fish might explain individual differences in vulnerability to fishing. If so, fishing could impose selection on fish behavior. In this study, we assessed boldness-indicating behaviors of Eurasian perch Perca fluviatilis using individually conducted experiments measuring the time taken to explore a novel arena containing predator (burbot, Lota lota) cues. We studied if individual differences in boldness would explain vulnerability of individually tagged perch to experimental angling in outdoor ponds, or if fishing would impose selection on boldness-indicating behavior. Perch expressed repeatable individual differences in boldness-indicating behavior but the individual boldness-score (the first principal component) obtained using principal component analysis combining all the measured behavioral responses did not explain vulnerability to experimental angling. Instead, large body size appeared as the only statistically significant predictor of capture probability. Our results suggest that angling is selective for large size, but not always selective for high boldness.

Does Angling Technique Selectively Target Fishes Based on Their Behavioural Type?

Recently, there has been growing recognition that fish harvesting practices can have important impacts on the phenotypic distributions and diversity of natural populations through a phenomenon known as fisheries-induced evolution. Here we experimentally show that two common recreational angling techniques (active crank baits versus passive soft plastics) differentially target wild largemouth bass (Micropterus salmoides) and rock bass (Ambloplites rupestris) based on variation in their behavioural tendencies. Fish were first angled in the wild using both techniques and then brought back to the laboratory and tested for individual-level differences in common estimates of personality (refuge emergence, flight-initiation-distance, latency-to-recapture and with a net, and general activity) in an in-lake experimental arena. We found that different angling techniques appear to selectively target these species based on their boldness (as characterized by refuge emergence, a standard measure of boldness in fishes) but not other assays of personality. We also observed that body size was independently a significant predictor of personality in both species, though this varied between traits and species. Our results suggest a context-dependency for vulnerability to capture relative to behaviour in these fish species. Ascertaining the selective pressures angling practices exert on natural populations is an important area of fisheries research with significant implications for ecology, evolution, and resource management.

Animal personality as a cause and consequence of contest behaviour

We review the evidence for a link between consistent among-individual variation in behaviour (animal personality) and the ability to win contests over limited resources. Explorative and bold behaviours often covary with contest behaviour and outcome, although there is evidence that the structure of these 'behavioural syndromes' can change across situations. Aggression itself is typically repeatable, but also subject to high within-individual variation as a consequence of plastic responses to previous fight outcomes and opponent traits. Common proximate mechanisms (gene expression, endocrine control and metabolic rates) may underpin variation in both contest behaviour and general personality traits. Given the theoretical links between the evolution of fighting and of personality, we suggest that longitudinal studies of contest behaviour, combining behavioural and physiological data, would be a useful context for the study of animal personalities.