Controlled experiments to explore the use of a multi-tissue approach to characterizing stress in wild-caught Pacific halibut (Hippoglossus stenolepis)

Anita C Kroska; Nathan Wolf; Josep V Planas; Matthew R Baker; T Scott Smeltz; Bradley P Harris

doi:10.1093/conphys/coab001

Controlled experiments to explore the use of a multi-tissue approach to characterizing stress in wild-caught Pacific halibut (Hippoglossus stenolepis)

Conserv Physiol. 2021 Feb 5;9(1):coab001. doi: 10.1093/conphys/coab001. eCollection 2021.

Authors

Anita C Kroska¹, Nathan Wolf¹, Josep V Planas^{1

2}, Matthew R Baker^{1

3}, T Scott Smeltz¹, Bradley P Harris¹

Affiliations

¹ Fisheries, Aquatic Science, and Technology Laboratory, Alaska Pacific University, 4101 University Dr., Anchorage, AK 99508, USA.
² International Pacific Halibut Commission, 2320 W Commodore Way, Seattle, WA 98199, USA.
³ North Pacific Research Board, 1007 W 3rd Ave #100, Anchorage, AK 99501, USA.

Abstract

The integration of multiple tissues in physiological and ecological analyses can enhance methodological approaches, increase applications for data and extend interpretation of results. Previous investigations of the stress response in fish have focused primarily on cortisol levels in a single matrix-blood plasma-which confines interpretations of cortisol levels to a short temporal frame. Epidermal mucus has been proposed as an alternative or complement to plasma that may provide a view to cortisol levels over a different temporal window allowing comparative assessment. Here, we explore the potential for multi-tissue cortisol analysis using both plasma and epidermal mucus in Pacific halibut (Hippoglossus stenolepis). The relative timing at which cortisol increased and decreased in the two matrices as well as cortisol concentrations at estimated peak levels were compared in two trials after (i) inducing cortisol synthesis by adrenocorticotropic hormone (ACTH_1-24) administration and (ii) inducing cortisol elimination using cortisol (hydrocortisone, 98%) injection. The ACTH treatment elicited a peak plasma cortisol response approximately 12 hours post-injection, while mucus cortisol concentrations peaked later at approximately 62 hours post-injection. Exogenous cortisol treatments suggested relatively little transfer of cortisol from plasma to mucus, potentially reflecting differential effects of endogenous and exogenous cortisol. Our results suggest the potential utility of mucus as a sampling matrix that provides an extended window for detection of the stress response as compared to plasma. Results also suggest the utility of a multi-tissue approach to cortisol analysis with potential applications to applied fisheries research. Increased understanding of the relative scale of the cortisol response to stress (e.g. capture) will allow researchers and managers to better interpret the physiological condition and survival outcome of fish subjected to regulatory discard.

Keywords: Cortisol; Pacific halibut; dynamics; epidermal mucus; plasma.