Environmental conditions and occurrence of hypoxia within production cages of Atlantic salmon on the south coast of Newfoundland

Abstract

Dissolved oxygen (DO) levels were monitored in two marine Atlantic salmon (Salmo salar L.) cage sites on the south coast of Newfoundland (Canada) during the summer and fall of 2008 and 2009. In 2008, sites A and B had cages with stocking densities of approximately 9 kg m À 3 . In 2009, site A was being fallowed while stocking density at site B was of 10 kg m À 3 . During 2008 and 2009, few hypoxic events (de¢ned as DO o6 mg L À 1 O 2 ) were recorded at site A; however, at site B intermittent hypoxic events (46 mg L À 1 O 2 ) were observed. Our study provides a description of intermittent hypoxia occurring in salmon cages. These hypoxic events occur mostly during the summer season and last for as long as 2.5 months. Fish swimming behaviour show that water layers exhibiting low DO did not cause avoidance behaviour. This con¢rms results found by other authors. Site B exhibited low water currents below 5 m suggesting that caution should be taken before considering an increase in stocking densities in cages. Questions remain about the e¡ect of this intermittent hypoxia on ¢sh health and growth, and will be the focus of future research.

Developmental Hypoxia Has Negligible Effects on Long-Term Hypoxia Tolerance and Aerobic Metabolism of Atlantic Salmon (Salmo salar)

“…Wild and cultured salmonids are also likely to experience fluctuating DO levels during postlarval rearing. For example, salmonids reared in marine sea cage aquaculture can experience significant DO variations over temporal and spatial scales (Johansson et al 2006;Oppedal et al 2011;Burt et al 2012).…”

Aplasia of the septum transversum has no effect on plasma biochemistry following an acute hypoxic event in Atlantic salmon

“…KEY WORDS: Aquaculture · Fish welfare · Heart · Stress · Cardiovascular · Hypoxia · Oxygen saturation · Salmo salar Resale or republication not permitted without written consent of the publisher 2011a, Burt et al 2012, and low values may be seen during management practices such as handling, crowding, topical de-licing or anti-lice practices (e.g. .…”

Cage size affects dissolved oxygen distribution in salmon aquaculture

“…Poor DO conditions, below levels known to cause reduced feed consumption and in some cases even death, have been documented in standard commercial salmon cages (12 500 to 24 500 m 3 ) on 3 continents (Bergheim et al 2006, Johansson et al 2007, Burt et al 2012, Stehfest et al 2017. For this reason, any alterations to production strategy which may in crease the likelihood of poor DO conditions, such as in creasing cage size, should be approached with caution.…”