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Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00401

    What is the limit of sustained swimming in Atlantic salmon post smolts?

    Malthe Hvas*, Ole Folkedal, Frode Oppedal

    *Corresponding author:

    ABSTRACT: A trend in Atlantic salmon aquaculture is to establish new production sites that are susceptible to extreme weather conditions. Strong and persistent water currents may here compromise fish welfare. To define acceptable current conditions necessitates assessments of sustained swimming abilities that is fuelled solely by aerobic metabolism and does not result in fatigue. In this study, the limit of sustained swimming was quantified with regards to both speed and time in Atlantic salmon of ~700 g and ~39 cm at 12°C by testing fish in groups of 10 in a large swim tunnel respirometer. First, critical swimming speed (Ucrit) (107 cm s–1) and minimum cost of transport (66 cm s–1) were measured. Sustained swimming trials at constant speeds were then performed based on a percentage of the group mean Ucrit (80, 85, 90, 95, 100 or 105%). Fish were here forced to swim until they fatigued, or until 72 h had passed. To our surprise, most fish were able to sustain 80 and 85% Ucrit for 72 consecutive hours. However, at the highest speeds, fatigue was reached within the first 2 h. By categorizing fatigue times of individual fish into <2 h, 2–72 h, or >72 h, significant differences in relative swimming speeds were found that corresponded to 2.7, 2.5 and 2.2 body lengths s–1, respectively. These results document impressive sustained swimming capacities in farmed Atlantic salmon and adds important temporal insights in ambient current limits with regards to fish welfare at exposed aquaculture sites.