CONTAINMENT SPECIAL
who should advise on whether a change to the cage and/or mooring specification is required. Any required alterations should be implement- ed by the farmer before the site is stocked or the new elements of the installations are used.
Interaction with other marine users Collision with non-aquaculture marine traf- fic has not been identified as a cause of an escape in Scotland since records began in May 2002, although there was at least one incident prior to this. Nevertheless, this issue has been of concern in the Mediterranean, where it has led to at least one major escape incident. An industry level discussion should be held with the Maritime and Coastguard Agency (MCA) and other organisations in regard to collision prevention approaches for fish farm instal- lations and any recommendations should be taken forward.
Design testing and provision of information to farmers It appears that there is little information available to aid farmers in their choice of equipment, other than manufacturers’ bro- chures and sales literature. This particularly relates to empirical data on cage performance and mooring design in different environmental conditions. It was recommended that research into the stresses and design limitations of dif- ferent types of equipment be undertaken to help address this issue.
Land-based farms and stock transfers
Freshwater tank sites
While escapes from screen failure are rela- tively few, they were identified throughout the study period and should be easily addressed. Aluminium tank screens are commonly used and can be easily damaged during routine operations, creating opportunities for escape incidents. Such escapes could be mitigated by the use of a ‘mortality tank’, outside the main fish tank, which can retain any escaping fish as well as collecting fish mortalities. The Code of Good Practice for Scottish Finfish Aquaculture (CoGP, 2006) requires that the outflow from a settlement pond is screened. The design of the screen should be such that fish cannot pass through the screen apertures or around the frame sides. Aluminium and plastic should not be used as a material for final screens discharging directly to a wa- tercourse. Consideration should be given to specifying the design of final outflow screens such that any ‘leakage’ escapees are retained by them. The use of a secondary system to contain escapes in the event of catastrophic
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tank failure is under discussion in Norway and should be considered in Scotland.
Transfer pipe failure Transfer pipes are used to move fish to and from wellboats and lorries. Transfer pipes should be inspected prior to use and during use, particularly just after starting the op- eration. Pipes with visible damage, including leaks, should not be used. There has been concern expressed about the older type of ‘mucon’ valve which led to one incident. The types of valves appropriate for use should be researched and specified. Secure methods of attachment from the pipe to the tanks and at each join of lengths of pipe should be pro- vided. They should be inspected prior to and during use. Consideration should be given to measures to ensure they remain secure during use.
Helicopter bucket incidents There were four helicopter bucket escape incidents during the study period, resulting in a reported loss of nearly 14,000 fish. Three of
OPPOSITE PAGE: ATTACHING A MOORING LEG TO A ROPE RING
– ANY SUCH JOINS SHOULD BE REGULARLY CHECKED
ABOVE: SAMPLING FISH WITH HAND NETS OCCASIONALLY LEADS TO AN ESCAPE
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