World Aquaculture Society Meetings

Add To Calendar 20/02/2017 15:15:0020/02/2017 15:35:00America/ChicagoAquaculture America 2017offshore aquaculture in the southern california bight: an assessment of aquamodel parameter sensitivty and farm environmental performance   Room 13The World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY

offshore aquaculture in the southern california bight: an assessment of aquamodel parameter sensitivty and farm environmental performance  

James A. Morris, Jr., J. Barry King, and Jack Rensel
 NOAA National Ocean Service
National Centers for Coastal Ocean Science
 Coastal Aquaculture Siting & Sustainability
101 Pivers Island Road
Beaufort, North Carolina 28516

To assist with open ocean aquaculture development in the Southern California Bight, we have developed an AquaModel computer simulation for the first fish farm to be permitted in federal waters. AquaModel was chosen as the modeling platform because it is a validated model that is used around the world to provide real-time, simultaneous benthic and water column environmental performance.  The Rose Canyon Fisheries proposed farm plans to annually produce approximately 5,000 metric tons of California Yellowtail (Seriola dorsalis) valued over $80 million off the coast of Southern California.  AquaModel benthic simulations suggested that increases in total organic carbon (TOC) under the cage array increases from the ambient concentration of 0.01% of the total mass of sediment materials to a maximum of 0.012% of total mass, an 18% increase in TOC, but a 0.0018 fractional increase in sediment total mass.  This increase is negligible and within natural background variation in TOC. Sediment sulfide increased slightly during neap (low flow situations), and quickly returned to zero when near sea floor flows returned.  The highest recorded value of sulfide was 530 µM. The presence of sulfides in the sediment typically lasted for less than a day.  Increase in sulfide was not observed 100 meters from the cage array. Sediment DO typically ranged between 3.3 and 4.6 ppm, depending on the DO content and flow of the ambient ocean directly at the seafloor.  Ambient bottom oxygen was field measured at 3.8 ppm in winter months. The lowest singular sediment DO was calculated as 1.86 ppm at a bottom flow of 0.95 cm/s and lasted only one hour before the current increased and DO returned to average values. Average surface water velocity was 18 cm/sec.  With a 26 m diameter cage, the total water volume is changed every 2.6 minutes, which carries heavy supply of DO and dilutes excreted ammonia to nearly indiscernible concentrations near and inside the cage. Prevailing dispersive bottom current direction was to the SSW (205 degrees) and therefore away from shore. Water column DO immediately downstream of the highest density cage during lowest flow periods (0.8 cm/s) was calculated to be 6.78 ppm compared to ambient which was 7.4 ppm.  Decreases in cage DO was not detectable during medium and high current flow periods. The highest observed dissolved nitrogen concentration was calculated to be 1.1 mg-at/m3 (0.015 ppm) which was 0.008 ppm above background during low surface flow periods inside the cage.  This increase in nitrogen is diluted within a few 10's of meters of the cage array depending on current direction and velocity. Subsequently, it is assimilated by phytoplankton that may be grazed by zooplankton that can be modeled with the AquaModel3D far field application also developed for this project. These results provide a first case study of marine cage culture environmental performance in the Southern California Bight.

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