Quantifying and modelling of the nitrogenous wastes associated with the commercial culture of Atlantic cod (Gadus morhua L.)

• Main Author: Oliver, Robert L.A.
• Other Authors: Telfer, Trevor, Roy, William, Seafish Highlands and Islands Enterprise, School of Natural Sciences, Aquaculture
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Institute of Aquaculture 2008
• Subjects: Atlantic cod (Gadus morhua L.); Nitrogenous wastes; Atlantic cod; Fishes Nutrition; Nitrogen cycle; Marine biology Scotland; Norway; atlantic cod; Atlantic salmon; Gadus morhua; Salmo salar
• Online Access: http://hdl.handle.net/1893/1741; http://dspace.stir.ac.uk/bitstream/1893/1741/1/Drew%20Thesis%20v2.pdf

In Scotland, environmental regulation restricts commercial cod culture to the equivalent of 66 % of that granted for commercial Atlantic salmon (Salmo salar L.) farms. This calculation is based on estimations of nitrogen discharge from the difference in protein content between salmon and cod diets, with the higher levels of protein in cod diets suggesting a higher nitrogen discharge compared to that observed for salmon diets. In turn, this could potentially result in increased nitrogen enrichment of a marine ecosystem. The aims of this study (quantifying and modeling of nitrogenous wastes associated with the commercial culture of Atlantic cod (Gadus morhua L.) were achieved through a series of tank and cage investigations, each of which studied juvenile and adult Atlantic cod. The study provided data with respect to nitrogen excretion from juvenile and adult fish in both systems. This would allow the development of dispersion models and the calculation of nitrogen budgets for commercial cod culture, thus providing environmental regulators data independent of salmon models to create regulations that would be specifically applied to cod farming. The tank - based studies investigated three diet formulations produced by EWOS® Innovation in Norway, as a 4 mm pellet (juvenile study) and as a 7 mm pellet (adult study). The three iso -energetic diets varied primarily in protein content (40 %, 50 % and 60 %). Two tank studies, one on juvenile and one on adult cod, investigated growth, condition and tissue composition, and the production of dissolved nitrogenous wastes over a 5 and 7 month period respectively. At the beginning of the acclimation period prior to the adult tank study commencing, the fish had a mean weight of approximately 1275 g. The difference in the final weight promoted by each diet was not significant (with an approximate final weight of 2400 g), suggesting that a low protein diet (40 % protein) promoted similar growth to a high protein diet (60 % protein). Other growth and condition parameters were ...