Aquaculture potential of Atlantic wolffish (Anarhichas lupus): stress and physiological responses to acute handling.

The Atlantic wolffish (Anarhichas lupus) is a cold-water species with the potential to diversify aquaculture in Northern countries. Few studies have investigated the stress physiology of Atlantic wolffish, and the current knowledge on stress in wolffish species is largely derived from the closely related spotted wolffish (Anarhichas minor). In the current study, Atlantic wolffish were exposed to handling stress mimicking common husbandry conditions in aquaculture such as repeated air exposure and net-chasing. Samples were taken prior to stress exposure (pre-stress; control) as well as 5- and 24-h post-stress. A series of primary and secondary acute stress response parameters were assessed: plasma cortisol, glucose and lactate levels, hematological indices (hemoglobin, Hb; hematocrit, Hct; mean corpuscular hemoglobin concentration, MCHC), and osmoregulatory capacity through plasma osmolality and gill Na⁺/K⁺ATPase (NKA) activity. Other secondary stress responses with implications for fish health and welfare are intestinal integrity and transport functions. These parameters were assessed using the Ussing chamber technique. The cortisol peak values were low in comparison to other fish species studied after acute handling stress and occurred as late as 24 h post-stress, suggesting that Atlantic wolffish is a slow and low cortisol responder. Plasma glucose remained stable, whereas lactate concentrations significantly decreased between 5 and 24 h after stress. There was no effect on pH, Hb, or Hct, although a significant increase in MCHC was found after 5 h and 24 h, originating from a small increase in Hb. This result suggests a minor increase in Hb synthesis after stress exposure. The intestinal integrity and transport functions as well as gill NKA-activity remained unchanged after stress exposure. In conclusion, Atlantic wolffish appears to exhibit a relatively moderate stress response, characterized by a slow and low primary stress response and minimal secondary effects following husbandry-related acute stress. These findings contribute to the understanding of the species' potential for development as a candidate for marine, cold-water aquaculture.