The following factors determine of we consider a site ‘offhsore’:
Location of sites:
To be considered an offshore site it must have the right combination of good water flow and wave action (high energy) and coarse sand sediment on the seafloor.
A combination of fast water movement and wave action (regularly greater than 4m) equates to a high energy site. This results in more oxygen availability and quicker flushing of carbon dioxide and ammonia which is much better for the fish. The higher energy of the water movement also reduces any impacts on the sediment and water column.
A coarse sand seabed is ideal for safe and sustainable salmon farming. The coarser, more mobile sediment under the pens is better oxygenated which means that any nutrient load (organic matter) is broken down more quickly.
The mix of high energy and inorganic coarse sand sediment is only typically found in exposed sites and they are the two factors that we combine to consider an offshore farming site. It’s not necessarily about distance from the shore, but rather having the right criteria such as wind, waves, current and suitable sediment type. Overall, this means that offshore sites have less impact on the environment than an inshore site for the same farming activity.
How do we find new potential offshore sites?
We use the best available environmental and meteorological information by undertaking joint projects with the Bureau of Meteorology to understand long-term wave and wind patterns in a variety of different locations. This is then cross-referenced by Huon with seafloor surveys and continuous in-situ monitoring over extended periods of time to assess wave and current information as we narrow the range of prospective lease locations.
Where to next?
Huon is undertaking a research project to investigate the potential of off-shore farming off the east of Cape Connella on Bruny Island. Click here to find out more.