subside is the only option. Frequently this means that what begins as a minor issue,
combined with adverse conditions over several days, eventually causes major
damage and there is absolutely nothing on-site personnel can do to prevent it. In
some cases main component issues such as mooring failures or broken structural
pieces will not result in a permanent setback to a project. Other situations, however,
such as gaping holes in netting, cages breaking free and going adrift/sinking, or
catastrophic failure of an entire cage system present an entirely different set of
circumstances. The offshore environment is extremely challenging and it should be
noted that every project in the GoM to date has had one or several of these events
occur, often simultaneously.
In addition to the high energy environment of the GoM, another serious issue
with netting and other containment materials is biofouling. The wave and current
forces exerted on the cage systems stress the components and as barnacles,
hydroids, and other organisms accumulate this stress increases. Antifouling paint
and other coatings are available and were applied to cage materials however these
are meant to reduce biofouling and are not capable of eliminating it altogether. Each
year during the spring and early summer the GoM waters begin to warm and a
significant amount of fouling occurred very quickly on the cage systems. The only
options available are to either clean a cage in place or replace components when the
accumulation becomes severe. Needless to say, the challenge of changing a 30–
40 m diameter net that weighs several tons in the offshore GoM environment
resulted in the cleaning option being employed. Figure 13.4 shows the preventative
effect of copper based antifoulant paint on fiberglass panels on the left, with the top
row being the treated samples. On the right the drag created by a virtual carpet of
hydroids is seen on cage netting in a strong current. In addition to creating additional stress on all the system components, the deformation of much of the netting
also effectively reduced the cage volume significantly. Any future offshore projects
in the Gulf, however, will have to seriously consider biofouling and how to prevent
and adequately deal with the inevitable growth of numerous marine organisms,
particularly on the netting or containment materials.
Logistically speaking, operating at exposed locations offshore is significantly
more expensive than onshore and near shore sites, largely due to transportation
costs. Personnel, cage systems, maintenance equipment, fish, and feed are some of
items that have to be transported by either air or sea to the project site whether the
platform involved is manned or unmanned. Both platform situations have been tried
during the GoM projects and each had its advantages as well as disadvantages.
Certainly having a large, stable structure with multiple decks, living quarters, a
power supply and crane in an otherwise uninhabitable offshore environment is an
asset to an aquaculture venture. In the two projects off the coast of Texas, cages
were either attached directly to the legs of a platform or mooring lines from the
system were connected to the structure(s) at various points as shown in Fig. 13.5.
380
J.B. Kaiser and M.D. Chambers
combined with adverse conditions over several days, eventually causes major
damage and there is absolutely nothing on-site personnel can do to prevent it. In
some cases main component issues such as mooring failures or broken structural
pieces will not result in a permanent setback to a project. Other situations, however,
such as gaping holes in netting, cages breaking free and going adrift/sinking, or
catastrophic failure of an entire cage system present an entirely different set of
circumstances. The offshore environment is extremely challenging and it should be
noted that every project in the GoM to date has had one or several of these events
occur, often simultaneously.
In addition to the high energy environment of the GoM, another serious issue
with netting and other containment materials is biofouling. The wave and current
forces exerted on the cage systems stress the components and as barnacles,
hydroids, and other organisms accumulate this stress increases. Antifouling paint
and other coatings are available and were applied to cage materials however these
are meant to reduce biofouling and are not capable of eliminating it altogether. Each
year during the spring and early summer the GoM waters begin to warm and a
significant amount of fouling occurred very quickly on the cage systems. The only
options available are to either clean a cage in place or replace components when the
accumulation becomes severe. Needless to say, the challenge of changing a 30–
40 m diameter net that weighs several tons in the offshore GoM environment
resulted in the cleaning option being employed. Figure 13.4 shows the preventative
effect of copper based antifoulant paint on fiberglass panels on the left, with the top
row being the treated samples. On the right the drag created by a virtual carpet of
hydroids is seen on cage netting in a strong current. In addition to creating additional stress on all the system components, the deformation of much of the netting
also effectively reduced the cage volume significantly. Any future offshore projects
in the Gulf, however, will have to seriously consider biofouling and how to prevent
and adequately deal with the inevitable growth of numerous marine organisms,
particularly on the netting or containment materials.
Logistically speaking, operating at exposed locations offshore is significantly
more expensive than onshore and near shore sites, largely due to transportation
costs. Personnel, cage systems, maintenance equipment, fish, and feed are some of
items that have to be transported by either air or sea to the project site whether the
platform involved is manned or unmanned. Both platform situations have been tried
during the GoM projects and each had its advantages as well as disadvantages.
Certainly having a large, stable structure with multiple decks, living quarters, a
power supply and crane in an otherwise uninhabitable offshore environment is an
asset to an aquaculture venture. In the two projects off the coast of Texas, cages
were either attached directly to the legs of a platform or mooring lines from the
system were connected to the structure(s) at various points as shown in Fig. 13.5.
380
J.B. Kaiser and M.D. Chambers