Refinement of computer models for determining distribution of finfish
aquaculture wastes and transfer of technology to regulatory agencies
Newell, C.R., Great Eastern Mussel Farms, Inc., Tenants Hbr., Me., USA and
V.G. Panchang, Dept. of Civil Engineering, University of Maine, Orono, Me. USA
ABSTRACT
Considerable effort is being invested in making measurements of
hydrodynamic, water quality and benthic parameters for monitoring and
regulating the environmental impacts of marine finfish cage culture. The
associated costs, generally borne by the industry, are large. Further,
discrete measurements over limited time periods at specific sites do not
give a truly representative overall picture; they cannot address spatial and
temporal variations within lease sites or the the cumulative effects of
several operations within a coastal embayment. In a previous project funded
by NOAA NMFS (technical report Maine Sea Grant TR-93-1), we have evaluated
mathematical computer modelling methods and demonstrated their effectiveness
in resolving these difficulties. We have recommended a ste-wise
comprehensive modelling strategy that involves a systematic investigation of
tidal and storm-induced currents, wave effects, waste transport (using a
particle tracking model), resuspension, and decay. These models, if accepted
by regulatory agencies, can result in significant cost savings to the
industry.
In our new project (November 1995 - April 1997) we wish to determine,
via measurements using a field-deployed annular flume called the Sea
Carousel, the critical shear velocity at which settled wastes are eroded and
resuspended. At present, this information does not exist and this aspect was
observed to be a critical parameter affecting lateral spread of particulate
aquaculture waste.
We also propose to package all the models in a form usable by state and
federal regulators, and transfer the technology (hardware and software) to
regulators in Maine, who may apply the product to routine monitoring of
existing lease sites and evaluation of potential new lease sites in Maine.
In addition, we will examine model predictions relative to existing data on
sediment granulometry and visual video transects at several study sites in
Cobscook Bay, Washington County, Maine. It is anticipated that at least
half of the finfish aquaculture sites currently monitored are highly
erosional and costly monitoring of those sites may not be necessary.