Exploring the relationship between stress coping styles and sex, origin and reproductive success, in Senegalese sole (Solea senegalensis) breeders in captivity.

Individual animals commonly adopt different stress coping styles that have been shown to impact reproductive success and differ between sexes (female/male) and origin (wild/hatchery). Hatchery reared Senegalese sole (Solea senegalensis) exhibit a behavioural reproductive dysfunction and a complete failure to spawn viable eggs. Hence, the present study examined whether 1) reproductive success of Senegalese sole was linked to coping styles and 2) behavioural differences exist in relation to sex or origin. A total of 198 breeders held in two research institutions were submitted to three individual tests (restraining, new environment and confinement) and one grouping test (risk taking). In addition, a blood sample to quantify cortisol, glucose and lactate levels was obtained from each individual after completing the individual tests. Senegalese sole breeders showed individual differences in behaviour across the different behavioural tests that were consistent with proactive and reactive coping styles traits. However, the most striking result was that reproductive success, sex and origin of Senegalese sole was not biased to any specific coping style. Indeed, the behavioural responses were similar and consistent between fish grouped by reproductive success, sex and origin. This study presented information that contrasts with different studies on dominant aggressive species and indicated that social non-aggressive species such as Senegalese sole follow a cooperative strategy that favours equal opportunities between stress coping styles and sexes. Therefore, results suggest that maintaining both coping styles strategies are fundamental for a sustainable breeder population approach.

Senegalese sole (Solea senegalensis) coping styles are consistent over time: behavioural and physiological responses during ontogenesis.

Individuals differ in how they cope with stressful situations along a behavioural continuum, being proactive and reactive at the extremes of this continuum. Proactive individuals are usually bold, highly active and take risks, while reactive organisms are generally shy, exhibit low activity and avoid risky situations. Definitions of stress coping styles state that proactive and reactive traits are consistent over time and across contexts. The present study evaluated the individual differences in stress coping style, physiological changes and reproductive status in Senegalese sole juveniles and breeders over three and two-years, respectively. To determine stress coping style, the fish were subjected to three individual (restraining, new environment, confinement) and one group screening test (risk taking). Both groups were tested on three occasions, juveniles were tested each year and adults were tested in the first year and twice (spring and autumn) in the second year. On the third year, a proportion of the juveniles initiated puberty and the reproductive status of all individuals was assessed and compared with their behavioural responses. Results demonstrated individual differences that were consistent with proactive and reactive traits in juveniles and breeders. Significant intra-individual repeatability and consistency of juveniles and breeder's behavioural responses were observed over time and across situations. In addition, glucocorticoid levels (cortisol) were consistent for individuals. Another result to highlight was that juveniles that past puberty and initiated gametogenesis had significant higher activity, risk predisposition and lower plasma cortisol levels compared to fish that remained immature (did not initiate puberty).

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.