Amoebic gill disease increases energy requirements and decreases hypoxia tolerance in Atlantic salmon ( Salmo salar ) smolts

• Published in: Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
• Main Authors: Bowden, AJ, Adams, MB, Andrewartha, SJ, Elliott, NG, Frappell, PB, Clark, TD
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Inc 2022
• Subjects: Agricultural; Veterinary and Food Sciences; Fisheries sciences; Aquaculture; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.1016/j.cbpa.2021.111128; http://www.ncbi.nlm.nih.gov/pubmed/34952237; http://ecite.utas.edu.au/152033

Globally, Atlantic salmon ( Salmo salar Linnaeus) aquaculture is now routinely affected by amoebic gill disease (AGD; Neoparamoeba perurans ). The disease proliferates throughout the summer and is implicated in decreasing tolerance of salmon to environmental perturbations, yet little empirical evidence exists to support these observations. Using salmon acclimated to 15 or 19C, our aim was to determine the effects of clinically light-moderate (industry-relevant) AGD on metabolism ( Ṁ O 2rest and Ṁ O 2max ), aerobic scope ( Ṁ O 2max Ṁ O 2rest ), excess post-exercise oxygen consumption (EPOC), and hypoxia tolerance. An increase in Ṁ O 2rest (~8% and~13% increase within the 15 and 19C acclimation groups, respectively) with increasing disease signs demonstrated an increase in baseline energy requirements as the disease progressed. Conversely, Ṁ O 2max remained stable at both temperatures (~364mg O 2 kg −1 h −1 ), resulting in a decline in aerobic scope by 13 and 19% in the 15 and 19C groups, respectively. There was evidence of a decrease in hypoxia tolerance as the dissolved oxygen concentrations at loss of equilibrium increased by ~8% with more severe lesion coverage of the gills. These results suggest an increase in basal energy requirements and reduction in hypoxia tolerance as AGD proliferates, lending support to the idea that AGD reduces environmental tolerance. However, the lack of an effect of acclimation temperature indicates that the temperature-disease interaction may be more complicated than currently thought.