SARF 054
CONTAINMENT SPECIAL
tidal range, current, nature of the seabed as well as fish husbandry and welfare etc. The study recommends that appropriate environmental data appropriate for design- ing moorings and specifying cages should be collected for establishing a new cage site or modifying an existing one. This should include a specified range of variables and time period, including when conditions would be expected to be at their worst.
ations where cages are close to the shore and there is suitable substrate. It may occasionally be used in areas with a rocky sea bed. While many farmers prefer the use of moor- ing pins where possible, as they are considered to be extremely reliable, one event was identi- fied where a line of rock pins failed in bad weather, indicating that rock pins can also be subject to failure.
Use of mooring professionals In most, though not all, cases, the moorings and cages at new sites will now be specified by an independent professional engineer. How- ever, there are still some instances where an installation may be designed on the basis of experience and local knowledge. Such an ap- proach may not provide a guarantee that the correct environmental information has been used in the design. Nor does it ensure that appropriate calculations of forces have been undertaken and that components are manu- factured to the quality standards required to meet those forces.
The study team recommended that moor- ings and cages should be designed by suitably qualified and experienced persons. Alterna- tively, the farmer’s design should be approved by a suitably qualified third party. It may also be worth considering an accreditation scheme for mooring and cage designers. It is likely that a number of existing sites remain which have not been designed by engineers. Although to some extent these have proved themselves by the passage of time, the damage caused by the 2005 hurricane illustrates that farmers should ensure that all sites have been designed to meet the full range of environmental conditions that could be expected.
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Environmental monitoring Moorings and cage specifications should be designed with full recognition of environmental conditions, including wind speeds, wave data,
With one exception, farmers were not aware of the environmental conditions their mooring and cage installations had been designed to withstand. It is recommended that a specific re- turn period (for a one in xx years event) should be considered for the Scottish industry, based upon advice from meteorologists and engi- neers and taking due regard of severe weather events over the past two or three decades, as well as climate change. All installations should now be able to withstand weather conditions such as the January 2005 storm as a mini- mum, with an additional safety factor. A number of mooring failures – in both sea water and freshwater – appear to have started with the failure of a single component, such as a mooring line. Installations should be de- signed to allow for the failure of at least one such component, which should include the most strategic components – known as building in redundancy – without a breakdown in the overall system.
Farmers were also not aware of whether their installations had been designed to any specific engineering standards or if there was a universal standard for floating aquaculture installations. It is recommended that standards should be specified for the Scottish aquaculture industry.
Designing for the location Although the specification of installations in Scottish aquaculture has, in general, increased over time, there are no specific requirements. Given that cage and mooring failure has ac- counted for the highest proportion of escaped fish since records began in 2002, a standard which sets out the minimum requirements for all elements of the establishment of a new cage site or the modification of an existing one was recommended in the SARF 054 study. This would help prevent the recurrence of escapes in major storm events.
Such a standard should ensure that the site be designed to withstand the loads gener- ated on the installation by the environmental conditions that may be expected in that area – ie to be location and equipment specific. This means that installations at more exposed sites would require higher specifications than those in more sheltered areas and should apply to cages, barges, moorings and related compo- nents.
The technical standard NS 9415 is the mandatory basis for the design of aquaculture installations in Norway. The SARF 054 report recommended that the ICWG should consider whether some or all of this should be adopted
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