Finfish farming is going through major development with the emphasis on offshore farming in particular with new species. There are several cage designs being used successfully in inshore locations but these have proved ill suited to offshore applications. One exception to this has been a cage system developed and manufactured by Bonnar Engineering / Dunlop Oil and Marine. This system is based on floating hose technology from the oil and dredging industries.
In many countries there is increasing public and planning resistance to placing of cages in inshore locations primarily because of their impact on visual amenity. In addition it is well known that fish perform much better in offshore sites where the water exchange is invariably greater. This has and will lead to the industry moving farms further offshore. Due to the severe weather and sea conditions encountered the farmer needs to be certain that his valuable stock are secure. The Tempest range of cages can provide the farmer with the best solution. The cages are in use in some of the most exposed sites in the world and being operated successfully. Dunlop Oil and Marine are world leaders in the design, manufacture and supply of large bore hoses used at offshore oil loading terminals. Their technical expertise and high concern for quality means that they are well qualified to help the fishfarming industry in its move to more exposed locations. The constant wave motion at these sites exacts a heavy toll in terms of cumulative damage to the collar structure. The use of Dunlop hoses has been proven with some hoses still in use almost 20 years after installation. The farmer knows he is getting a quality product from an internationally renowned company backed up by a comprehensive after sales service and continuous development programme.
Full range of cages, to suit every need
Modular design allows for cages to be rafted together economically
• Inherent flexibility allowing cages to be moored in offshore conditions
• Prevailing offshore conditions give better water exchange
- Healthier, larger, and better quality fish
- Pollution/environmental problems eliminated
• Sea data/mooring studies available
• Large boats can moor alongside for service and maintenance
Cage Systems
The modular design of the Tempest cage system offers the fish farmer a number of options in the configuration of the farm. The cages can be installed as a single or double line or incorporated with hexagons in a grid system. Raft systems can result in significant cost savings as they can be extended by adding only three sides of the square to form an additional cage.
The cages incorporate flexible rubber hoses which are pressurised to provide the correct degree of bending stiffness in the cage structure. Rigid steel walkways can be fitted to each corner section to facilitate the safety of personnel working on the cage. The most common side length is 16 metres giving an enclosed area of 256 square metres. With a net depth of 10 metres and stocked at 15kgs to the cubic metre the maximum biomass is about 40 tons. To maintain net shape and volume a maximum weight of 1000kgs can be suspended from the collar.
Hexagonal Cages
These cages are similar in design to the Tempest Squares, incorporating pressurised flexible rubber hoses with the option of rigid steel walkways at both ends of each side. The most popular cage has 16 metre sides giving a surface area of 660 square metres. With a 10 metre deep net the enclosed volume is approximately 6,600 m3 giving a production capacity of around 100 tonnes.
The Tempest Hexagonal can be moored independently or in a grid system. The hexagonal cage can also be incorporated with squares to give the farmer maximum flexibility in production planning. To maintain net shape and hence volume up to 1.5 tonnes can be suspended from the collar.
Octagonal Cages
This cage is the most economical of all the cages in the range giving the lowest cost per square metre of enclosed area. As with the other Tempest cages, the Tempest Octagonal incorporates the same flexible hose technology, pressurised to provide the correct degree of bending stiffness in the cage collar. The corners can be fitted with rigid steel walkways to provide a safe working platform.
The most popular form of this cage is with 16 metre sides giving an enclosed area of 1235m2. With a 10 metre deep net the volume is approximately 16,000m3 giving a biomass production capacity of 200 tons at 15kgs/m3. To maintain net shape and hence volume up to 2000kgs of weight can be suspended from the collar. In most applications this cage is used as a production cage.
A 16 x 16 metre square has been developed which attaches to the octagon using one of the sides as the fourth side of the square. This square can be used for a number of purposes such as holding/starvation of fish for harvest, grading or holding extra biomass. This can be put on and removed at sea.
Workrafts
Harvesting
The raft can be fitted with a powerpack to run various applications hydraulically such as a paddlewheel, airlift or a brailler. The raft can be fitted with a harvesting line and provide a storage area for bins. It is easily towed short distances with an outboard and longer distances with a larger boat. Depending on the load profile the raft can draw as little as 1 metre so allowing access to tidal piers.
Net changing/farm maintenance
The raft can be fitted with a crane on a base supplied by us which can be used to change nets and other routine farm operations requiring a crane or a capstan.
Food storage
By fitting a crane the raft can be used to store food for boats to take off that may otherwise be unable to access a suitable pier. It can also be used to site an automatic feeding system for the smaller farm using bulk bags. A boat can be unloaded by the crane and the hopper filled by the same crane. Load carrying capacity can be easily accommodated at the design stage and all steelwork galvanised. The raft can be delivered by road as it is easily disassembled.
Other Products
• Seaboard Anchors
• Harvester Cages
• Rafts
• Pontoons
• Transporters
• Submersible Model
