Introduction
With the growing worldwide demand for seafood, and the depletion of many species in the natural environment aquaculture has become a crucial source of protein and now accounts for nearly half of the worldwide supply of fish consumed by humans.
The development of open ocean marine aquaculture (mariculture) farms within the United States Exclusive Economic Zone (EEZ) offers the promise of profitable commercialization with low risk to the environment and wild fish stocks.
Still concerns with the impact of fish farming on the ecosystem and with the quality of the fish grown require a thorough analysis of potential sites and other parameters of the mariculture operation.
System Science Applications with the support of the USDA, has expanded its site evaluation tool AquaModel so that it can be used by government agencies for planning, permitting and public relations. It also provides support for objective consulting services and decision support tools for the future offshore mariculture industry.
Expanded Capabilities (See menu tabs or click on links for detail)
- Displays detailed bathymetry
- Links to outputs from additional coastal flow models
- More advanced visualization of entire coastline
- Additional contouring and statistics capabilities
- Accelerated simulations of the impact of sediment waste deposition in waters where waste accumulation and the response of the benthic community is slow.
- Enhanced modeled benthic dynamics
Model Calibration by Growing Fish in a Laboratory
We have completed laboratory studies on the growth and metabolic activity of species that are candidates for large open water commercial farming in Hawai’i or in other tropical areas.
- Moi (Polydactylus sexfilis), which was the first species to be reared in net pens in Hawai'i
- Cobia (Rachycentron canadum), a fast growing species being cultured in a number of tropical locations worldwide.
The results of these physiological trials were used to construct mathematical physiological submodels for incorporation as computer code into AquaModel.
Development of a Mariculture Information System for Hawai'i
Using the updated AquaModel, We have developed a Mariculture Information System for the Island of Hawai'i. We incorporated the University of Hawai'i flow model and simulated the placement of both single and multiple fish farms there.
Observed Results
The simulations were run near the NW coast of the big island of Hawai'i where we forcasted water column and benthic effects.
Studies were run of both a single modestly-sized fish farm site and, for six slightly larger farms in the same region. We found:
- The strong currents and modest production schedule resulted in essentially no measurable adverse effect upon the seabottom anywhere in the modeling domain.
- Nearest shore, the concentration of net pen origin nitrogen would be near zero except for brief periods, particularly when the fish biomass was approaching maximum carrying capacity.
- Larger or more numerous fish farm sites could increase the concentrations near shore and possibly initiate a problem for the coral reefs.
- There were more optimal and less optimal sites in terms of phytoplankton accumulation and density.
- Effects nearshore were most pronounced from pens located inside the Kohala Coast bight, a sort of open bay that tended to reduce water flow.
- The production of phytoplankton at all locations was minimal.
This analysis indicates that some level of net pen based fish farming would be sustainable along the subject coastal area, but that there are limits or a carrying capacity where the effects would shift from non measurable or insignificant to measurable and potentially adverse.
Presently, AquaModel is the only computer software in the world that is specifically designed for forecasting these effects.