Hypoxia during incubation does not affect aerobic performance or haematology of Atlantic salmon (Salmo salar) when re-exposed in later life

• Published in: Conservation Physiology
• Main Authors: Wood, At, Andrewartha, SJ, Elliott, NG, Frappell, PB, Clark, TD
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2019
• Subjects: Atlantic salmon; hypoxia; aerobic capacity; Salmo salar
• Online Access: https://eprints.utas.edu.au/34073/; https://eprints.utas.edu.au/34073/1/139792%20-%20Hypoxia%20during%20incubation%20does%20not%20affect%20aerobic%20performance%20or%20haematology%20of%20Atlantic%20salmon%20when%20re-exposed%20in%20later%20life.pdf

Hypoxia in aquatic ecosystems is becoming increasingly prevalent, potentially reducing fish performance and survival by limiting the oxygen available for aerobic activities. Hypoxia is a challenge for conserving and managing fish populations and demands a better understanding of the short- and long-term impacts of hypoxic environments on fish performance. Fish acclimate to hypoxia via a variety of short- and long-term physiological modifications in an attempt to maintain aerobic performance. In particular, hypoxia exposure during early development may result in enduring cardio-respiratory modifications that affect future hypoxia acclimation capacity, yet this possibility remains poorly investigated. We incubated Atlantic salmon (Salmo salar) in normoxia (∼100% dissolved oxygen [DO, as percent air saturation]), moderate hypoxia (∼63% DO) or cyclical hypoxia (100-25% DO daily) from fertilization until 113 days post-fertilization prior to rearing all groups in normoxia for a further 8 months. At ∼11 months of age, subsets of each group were acclimated to hypoxia (50% DO) for up to 44 days prior to haematology, aerobic metabolic rate and hypoxia tolerance measurements. Hypoxia exposure during incubation (fertilization to 113 days post-fertilization) did not affect the haematology, aerobic performance or hypoxia tolerance of juvenile salmon in later life. Juveniles acclimated to hypoxia increased maximum aerobic metabolic rate and aerobic scope by ∼23 and ∼52%, respectively, when measured at 50% DO but not at 100% DO. Hypoxia-incubated juveniles also increased haematocrit and haemoglobin concentration but did not affect acute hypoxia tolerance (critical oxygen level and DO at LOE). Thus, while Atlantic salmon possess a considerable capacity to physiologically acclimate to hypoxia by improving aerobic performance in low oxygen conditions, we found no evidence that this capacity is influenced by early-life hypoxia exposure.