This version available http://nora.nerc.ac.uk/7671/ NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the authors and/or other rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access This document is the author's final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. Some differences between this and the publisher's version remain. You are advised to consult the publisher's version if you wish to cite from this article. www.elsevier.comContact CEH NORA team at nora@ceh.ac.ukThe NERC and CEH trade marks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. Wilson et al. 1994;Réale et al. 2007). Notwithstanding a certain lack of consensus in terminology, the evolution of these analogues of human personality has evoked considerable scientific interest. Among the questions raised are by which mechanisms behavioural syndromes are inherited, how the variation is maintained, which circumstances benefit different complex phenotypes, and what are the costs and benefits of limited plasticity imposed by more or less fixed trait associations (DeWitt et al. 1998;Koolhaas et al. 1999;Sih et al. 2004; Dingemanse and Réale 2005;McElreath et al. 2007;Réale et al. 2007;Wolf et al. 2007). Furthermore, in the barn owl (Tyto Alba) melanin-based colouration is associated with several behavioural, morphological and physiological characteristics that have been linked to stress coping ability (Almasi et al. 2008).Based on observations that HR and LR trout differed in melanin pigmentation our hypothesis was that spotted fish, in the closely related specie Atlantic salmon (Salmo Salar), 5 would show a lower cortisol reponse to stress when compared to a non-spotted group of individuals. Furthermore, several documented changes in the behaviour of the two trout lines made us predict that also behaviour would differ between groups of spotted and non-spotted fish. The main focus of this study was therefore to test the hypothesis that there exist an association between melanin-based pigmentation and hypothalamus-pituitary-interrenal (HPIaxis) reactivity in salmonid fish. Furthermore, we tested the prediction that behavioural differences are present in two groups of fish chosen divergently on melanin pigmentation. Materials and methods Quantification of melanin-based colorationIn the studies described below, photographs of experimental fish were captured with a Canon EOS 450D digital camera and transferred to a computer for further analyses of melanin-based coloration. Prior to photography, each fish were sedated in 200 mg/l MS-222 and placed adjacent to a measuring tape with millimetre resolution, allowing for an accurate estimation of the area where spots were counted. The d...

The aim of this study was to establish whether two lines of rainbow trout divergent for their plasma cortisol response to a standardized stressor would show consistent differences in their behavioural response to a range of challenging situations. Our results show that the high-and low-responding (HR and LR) lines of rainbow trout did not differ in the aggression shown towards an intruder or in their response to the introduction of a novel object to their home environment. However, there was a difference in behaviour between the two selection lines when they were exposed to two unfamiliar environments. These results suggest that the behaviour of the HR and LR fish differs when they are challenged in unfamiliar environments, while their behaviour does not differ when they are challenged in their home environment. These observations are in agreement with studies on mammals thatshow that individuals with reactive coping styles perform similarly to proactive animals when they are challenged in a familiar environment, while they show different behaviour when they are challenged in unfamiliar environments. Thus, these results provide further evidence that the HR and LR selection lines of rainbow trout exemplify the two different coping styles described in mammals.

Individual rainbow trout were transferred to visual isolation in experimental aquaria. As a measure of the speed of acclimation, individual food intake was quantified during the first 6 d following transfer. Following acclimation, aggression was quantified by subjecting the fish to three resident-intruder tests, with 30 d of recovery between the tests. Moreover, between the resident-intruder tests (i.e., two times) the fish were exposed to an unfamiliar environment and their cortisol response was measured. The results of this study show that individuals of juvenile rainbow trout differ distinctly in their response to changes in their environment, and that this diversity in behavior is reflected by consistent behavioral traits displayed by individual fish. These traits have proven to be consistent not only over time but also across situations, revealing two distinct behavioral profiles, in the same manner as shown in studies on proactive and reactive mammals. Our results also show that the reactivity of the hypothalamic-pituitary-interrenal (HPI) axis, when exposed to a stressor, is a consistent physiological trait in juvenile rainbow trout. We found that difference in HPI axis reactivity is linked to the different behavioral profiles. However, HPI axis reactivity could not be linked directly to the singular behavioral traits measured. In other words, we did not find that the consistent behavioral traits shown by the fish were associated with a difference in HPI axis reactivity in the same manner as the reactivity of the hypothalamic-pituitary-adrenocortical axis does in mammals. Taken together, our results show that stress coping strategies akin to what has been described as reactive and proactive stress coping in mammals appear to exist in juvenile rainbow trout.

It is becoming increasingly recognized that the diversity in stressors, their intensity, predictability and the context in which they are experienced, will result in behavioral and physiological responses just as diverse. In addition, stress responses are characterized by individual variations where the physiological and behavioral reactions are associated in such a manner that distinct stress coping styles encompassing suites of correlated traits can be identified. These are often referred to as proactive and reactive stress coping styles. Proactive coping is characterized by more aggression, higher general activity and higher sympathetic activation, whereas reactive coping is characterized by immobility, lack of initiative and a higher parasympathetic/hypothalamic activation. Stable coping styles appear to coexist within populations, and these strategies appear to be largely innate. Moreover, the physiological and behavioral traits of coping styles appear to be heritable. These stress coping styles have proven to play a major role in competitive ability and subsequent social position in different species of vertebrates. However, there are also studies showing that social position can affect parameters encompassing the stress coping style of individuals. In this regard it is important, but not always easy, to distinguish between causes and effects of behavioral and physiological responses to stressors. The question raised is to what extent and rigidness stress coping styles are guided by genetic factors.

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