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).