Preliminary model of nitrogen loads from southern bluefin tuna aquaculture

• Published in: Marine pollution bulletin 2007-09, Vol.54 (9), p.1321-1332
• Main Authors: Fernandes, Milena, Lauer, Peter, Cheshire, Anthony, Angove, Michael
• Format: Article
• Language: English
• Subjects: Animal aquaculture; Animal productions; Animals; Aquaculture; Benthic fluxes; Biological and medical sciences; Feces - chemistry; Fishes - metabolism; Fundamental and applied biological sciences. Psychology; Geologic Sediments - analysis; Marine; Models, Biological; Nitrogen; Nitrogen - analysis; Nitrogen - metabolism; Pisciculture; Sedimentation; Sediments; South Australia; Thunnus maccoyii; Vertebrate aquaculture
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2007.06.005

Farming of wild tuna in coastal areas is a relatively new aquaculture industry and little is known about the magnitude of nutrient discharges to the environment. In this work we present a preliminary model of nitrogen loads from southern bluefin tuna ( Thunnus maccoyii) aquaculture in lower Spencer Gulf, South Australia. The model was developed based on feed inputs, estimates of fish metabolism and environmental data. Two pens were monitored over a full grow-out season to determine nitrogen sedimentation fluxes, remineralization at the sediment–water interface and accumulation in the sediments. The model suggests that the high metabolic rates of tuna lead to low retention of nitrogen in fish tissues (7–12% of feed inputs) and high environmental losses (260–502 kg N tonne −1 growth). Considering Australian annual production of 4380 tonnes over initial stocked biomass, total loads can reach 1137 tonnes N per year, 86–92% lost as dissolved wastes. The nature of wastes suggests low localized impacts at current stocking densities and holding periods.