Evaluation of stress in farmed Atlantic salmon (Salmo salar) using different biological matrices
Rouzbeh Keihani, Ana S. Gomes, Pablo Balseiro, Sigurd O. Handeland, Marnix Gorissen, Augustine Arukwe
Abstract
Atlantic salmon were subjected to an acute crowding scenario, and their subsequent stress responses were observed under three distinct swimming speed/water flow (WF) conditions: 0.5, 1, and 1.5 body lengths per second (BL/s). Feces, dermal mucus, and plasma were collected for analysis at 1, 6, and 24 h (h) post-stress. Additionally, the head kidney and two regions of the brain (pituitary and POA) were collected for transcript expression analysis. Fish swimming at 0.5 BL/s exhibited higher pre-stress (baseline) cortisol levels. Across all groups and matrices, the highest cortisol/cortisol metabolites (CM) levels were observed at the 1 h post-stress sampling point. At 6 h (second sampling time point), a clear decline toward baseline levels were observe in all groups. Significant increases in mean plasma glucose levels were observed at 1 h post-stress for all groups. The mean plasma lactate levels varied based on WF treatments, with a significant increase observed at 1 h only for the 1.5 BL/s group. Additionally, significant decreases in mean plasma lactate were noted at 6 and 24 h post-stress for some groups. The mRNA abundances of the tested genes ( star, cyp17a1, hsd11β2, srd5a1 ) increased following the stress events. These changes were not uniform across all groups and were tissue dependent. In summary, the results indicate that mucus and feces can be used as potentially less invasive matrices than blood for evaluating stress and, consequently, the welfare of Atlantic salmon in captivity. • Highest cortisol/cortisol metabolites (CM) and glucose levels at the 1 h post-stress. • Clear decline of CM at 6 h post stress toward baseline levels in all groups. • Changes in plasma lactate levels based on water flow. • Tissue-dependent expression of star, cyp17a1, hsd11β2, srd5a1 increased based on stress events. • Data indicate that mucus and feces are less invasive matrices for evaluating stress and welfare in fish.