Establishing the optimal salinity for rearing salmon in recirculating aquaculture systems

• Main Author: Emerman, Joshua David
• Format: Text
• Language: English
• Published: University of British Columbia 2016
• Subjects: Atlantic salmon; Salmo salar
• Online Access: https://dx.doi.org/10.14288/1.0225868; https://doi.library.ubc.ca/10.14288/1.0225868

Aquaculture of salmon worldwide is a 15.3 billion dollar industry and the majority of fish are produced in net-pen systems in coastal waters. Recently producers have begun investigating the feasibility of moving salmon production onto land and into recirculating aquaculture systems (RAS). The major downsides to RAS are the startup and operational costs; however the ability to optimize many environmental variables to enhance growth and feed conversion, something impossible to do in net-pen systems, may help defray these otherwise prohibitive costs. Salinity may be the most important of these variables due to the metabolic cost of osmoregulation, which has been estimated to account for 5-50% of routine metabolic rate. Decreased osmoregulatory costs could result in a greater allocation of energy toward growth, thus shortening production times and improving feed conversion efficiency. To establish an optimal salinity for growth in salmon, seven replicate, 15,000 liter RAS were constructed at the University of British Columbia’s InSEAS research facility. I conducted a preliminary study to validate that each system was able to control water quality parameters and yield similar levels of growth and feed conversion in coho salmon (Oncorhynchus kisutch). I then conducted salinity trials with Atlantic (Salmo salar) and coho salmon. Fish were grown in five salinities ranging from freshwater to seawater (0, 5, 10, 20, 30 ppt) for approximately five months. Growth rates and feed conversion ratios (FCR) were measured throughout the trial. The fastest growth rate and lowest FCR in coho salmon was at 10 ppt, which is approximately isosmotic to the blood. Growth rate of coho at intermediate salinities was almost double that at 0 or 30 ppt through the first growth period. This trend was not seen during the second coho growth period, possibly due to a size-dependent or density effect. Unexpectedly, salinity had no effect on growth rate and FCR in Atlantic salmon, although growth rates were consistent with those seen in industry. This research will help further move salmon production out of the oceans and onto land, alleviating some of the environmental costs associated with salmon grown in the oceans.