S. Ferrari1*, M. F. Castanheira2, T. H. Evensen4, C. Martins2, C. Oliveira2, L. E. C. Conceição2, B. Chatain3, B. Damsgård4,5 and M.-L. Bégout1
(1) Ifremer, Place Gaby Coll, B.P. 7, 17137 L'Houmeau, France. (2) CCMAR-CIMAR L.A., Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal. (3) Ifremer, Chemin de Maguelone, 34 34250 Palavas-les-Flots, France. (4) Nofima, 9291 Tromsø, (5) Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, 9037 Tromsø, Norway.
E-mail: Marie.Laure.Begout@ifremer.fr
Introduction
In the context of aquaculture expansion and a growing awareness of fish welfare, several European projects were launched to improve fish production and welfare. Among them, FP7 COPEWELL project aims at developing a new integrative framework for the study of fish welfare based on the concepts of allostasis, appraisal and coping styles. In the last decades, studies on coping styles have demonstrated their implications in a wide range of fields, including behavioral ecology, neurosciences, aquaculture and welfare, health and diseases susceptibility and interpretations of molecular data. In the WP dedicated to coping styles, objectives are to establish non-invasive methods for reliable identification of contrasting stress coping styles, and to demonstrate and quantify the presence and consistency of individual variation in Atlantic salmon (Salmo salar), sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) using a combination of behavioral and physiological observations, gene expression and neuroendocrine analyses. The second aim is to provide a causal mechanism for the presence of welfare relevant trait correlations in farmed fish by addressing the genetic regulation of coping styles at the level of the transcriptome. The first step in this work was the characterization of coping styles and identification of their implications.
Material and methods
Individually tagged juveniles of the three species were used to investigate whether individual differences in behavioural responses to a variety of challenges were consistent over time and across contexts using both individual and grouped-based tests.
Seabass (N=30) were subjected to individual (exploration, restraining and aggression tests) and group-based tests (hypoxia test and risk taking test). Consistency over time (1.5 mo and 14 days respectively) and link with physiological responses were analyzed. Thereafter, in another experiment, seabass were screened for coping style using hypoxia test, then one triplicate (N=3x120) per coping styles (reactive, proactive, intermediate and 50/50 mix of reactive/proactive) were reared during 5mo and then submitted to an acute repeated stress (confinement twice a week during 3 weeks). Differential impact on growth and cortisol responses after an additional confinement stress were analyzed.
Seabream (N=24) were subjected to three individual-based tests (feed intake recovery in a novel environment, novel object and restraining) and two group-based tests (hypoxia test and risk-taking test). Each test was repeated twice over a period of 14 days. After the group testing an additional test was performed using the same individuals to determine individual differences in aggressiveness (aggression test). Furthermore, using another set of individuals (N=23) a confinement test inside a metabolic chamber was performed to determine individual differences in oxygen consumption.
Atlantic salmon: The correlations between individual behavioural traits and physiological stress responses were tested using individual-based tests (novel object, mirror test, novel environment) and a group screening test using oxygen avoidance (hypoxia test). A population of ca 500 fish were reared from juvenile to smolt stage (ca 60g, 10oC freshwater, surplus feeding). The population was unsorted, in order to keep the variation within the fish population and reflect a normal range in an aquaculture setting. A highly automatic group screening method was developed using two 200L tanks with a 10cm tunnel in between fitted with a PIT tag antenna. Eight groups of salmon were tested repeatedly during a highly controlled oxygen decline to 25% saturation, monitoring both the changes in water quality and ID of fish leaving to the other tank with 100% oxygen level. Samples from stressed and unstressed controls fish were collected for physiological, gene expression and neuroendocrine analyses.
Results
All studies allowed characterizing coping style in each species and the identification of divergent individual behavior, from reactive, intermediate to proactive fish.
Seabass: Group based tests appeared the most relevant for characterization of coping style. Individual behavior during hypoxia test appeared to be consistent over time and individual oxygen level to induce behavioral response was negatively correlated with plasma cortisol level after the test. Risk taking test was also consistent over time (14 days). In addition, risk-taker fish were more active than risk-avoiders and conversely. Furthermore, coping style and the manipulation of group composition appeared to have an impact on both growth and cortisol responses.
Seabream: Results showed that the behaviour during restraining and risk-taking tests was consistent over time. Consistency across contexts was also detected: individuals that tried to escape more in a restraining test, escaped faster from hypoxia, were more risk-takers and took longer to recover feed intake after transfer into a novel environment. In addition, individual differences in aggressiveness were significantly correlated with cortisol responsiveness after the net restraining test. Individual differences in oxygen consumption demonstrated that the latency to take risks was negatively correlated to activity and oxygen consumption rates, indicating that risk-avoiders (long latency) were less active and, hence, did not consume so much oxygen as risk-takers.
Atlantic salmon: The main results suggest that the oxygen avoidance test on the group level was most predictive for coping style. The fish population had no mortality and grew well during the experimental period, and developed a bimodal size distribution with a lower parr mode and a higher smolt mode. The behavioural patterns were different in the two modes, presumeably not only due to a size difference. In the hypoxia test, the fish that left the low oxygen tank had a significant lower plasma cortisol level compared to those which stayed, and this result could not be explained in terms of effects of the experimental design.
Discussion
The presence of coping styles is now well recognised in these species and their implications for aquaculture are broad. Individual fish within a population often differ in how strongly they respond, behaviourally and physiologically, under stress conditions. A failure to accommodate the coping strategies of fish under farming conditions can lead to problems linked with production (e.g. aggression, growth and disease resistance).
Taken together, the presence of coping styles in fish shows that screening for coping styles is species-specific. The recent development of group-based tests and the use of proxies may provide an opportunity for mass screening in the future. Mass screening into different coping styles may help optimizing the production systems as optimal conditions for proactive individuals are likely to be different from those of reactive individuals. In addition, the recognition that farmed fish exhibit coping styles means that a number of behavioural and physiological responses will vary as part of a common "package" that should be taken into consideration when designing breeding programs.
Acknowledgements
This research project has been supported by the European Commission under the 7th Framework Program FP7-KBBE-2010-4 Contract no.: 265957 COPEWELL