Cortisol and Behavioral Response to Handling (Acute) and Confinement (Chronic) Stressors in Juvenile Spotted Wolffish, Anarhichas minor

Abstract

The purpose of this study was to determine the cortisol response of spotted wolffish (Anarhichas minor) after exposure to air immersion and netting (acute stress) under a range of increasing densities (chronic stressor). In addition, the presence of a cumulative negative impact from chronic stress was assessed by the application of an additional acute stressor following rearing at various densities, and proxies of behavior were evaluated (feeding and aggression data). The stress response to air immersion and netting led to increasing plasma cortisol values at 0.5, 13, and 37 h post-stress, with the highest value achieved after 13 h. At 168 h, cortisol concentrations returned to similar pre-stress value. Changes in cortisol concentrations were relatively low after acute stress (five to six fold increases) and recovery time long lasting (>37 h). Prolonged rearing at 20, 30, and 40 kg m⁻² showed a non-significant trend of increasing cortisol values with increasing density, and the cortisol response after the application of an additional acute stressor was significantly altered, i.e., higher cortisol levels were measured in unstressed (chronic stress only) compared to stressed fish (chronic stress + acute stress). Our results suggest that (1) spotted wolffish is a low responder that additionally displays a long-lasting cortisol elevation following an acute stressor; (2) fixed densities did not lead to significant differences of plasma cortisol concentration or aggression levels, although involved marked changes in daily feed intake and food conversion efficiency were observed; and (3) cortisol levels reached acute stress values after prolonged chronic stress. Although this species displays indications of being relatively resistant to handling disturbances during aquaculture practices, it is nevertheless responsive to chronic stress factors that could alter the physiological response to subsequent acute stressor.

Keywords:

• Stress
• cortisol
• Anarhichas minor
• spotted wolffish
• density and behavior

Acknowledgments

*Nathalie R. Le François and Sarah Tremblay-Bourgeois contributed equally to this article.

The authors thank T. Grenier for technical assistance, A. Caron for statistical analyses, and J. W. Mandelman (New England Aquarium, Boston, ME, USA) for helpful comments on this article. This study was funded by the Ministère des Pêcheries et de l'Alimentation du Québec and the Société de Développement de l'Industrie Maricole to Nathalie R. Le François. Sarah Tremblay-Bourgeois was supported by student grants from NSERC and FQRNT.