CONTAINMENT SPECIAL
NO MORE NET CHANGING LIMITS THE CHANCE OF ESCAPES
while temperature of the water plays an impor- tant role, as this influences the types of fouling that dominate the process. ‘We have tested our product successfully in the Mediterranean market since early 2007. Nets we deployed then are still in use and, except for some microalgae, they are still com- pletely free of fouling, as is shown left.’
‘However,’ he continues, ‘in 2010 we have seen that the dominant species in the northern Atlantic differ from the Mediterranean and, consequently, we have needed to adapt our system to the local circumstances. Hydroids and mussels cause particular troubles in these waters. By the end of the summer, we were able to show that we can now also resist mus- sels and hydroids in water where these species are dominant’.
mesh was still free of fouling. ‘Even though this may have been an extreme case, as copper normally has a longer lifetime, it shows that Thorn D®
is resisting this species even in the extreme case.’
This is demonstrated by pictures taken at a Scottish fish farm where panels were deployed at the same time as full copper-treated netting. These clearly show that, after six weeks, the copper treated net needed cleaning while the Thorn-D®
Why does Thorn-D® Thorn-D®
save money?
needs to be applied only once. Though the initial investment is higher, cost savings will be reached after a period of between a year and 18 months – as no more dipping with copper antifouling or cleaning is needed. As Thorn-D®
adds up to 40 per cent
breaking load to the net, less maintenance is required as well. ‘Though the cost savings may be important, we increasingly get the impression that the biggest advantages are coming from the posi- tive containment effects that occur by using Thorn-D®
,’ adds Breur. ‘Since Thorn-D® lasts
for the lifetime of a net, there is no longer a need to change nets during the produc- tion cycle. As a consequence fish growth will increase.’
‘Normally before changing nets,’ he explains, ‘feeding is stopped for 2-3 days. Combined with reduced feeding during cleaning operations, the effective growth time for the salmon can increase by up to 10 per cent. Moreover, no more net chang- ing reduces the chance of fish escapes, an effect which doesn’t need to be expressed in money, as the benefit to sustainability is paramount.’
www.fishfarmer-magazine.com
OPPOSITE: NETTING IN THE MEDITERRANEAN – IN THE WATER SINCE EARLY 2007 (MESH SIZE 1.25 INCH)
ABOVE AND LEFT: NETTING WITH COPPER-BASED ANTIFOULING (LEFT) VERSUS THORN-D® (ABOVE) AFTER 6 WEEKS IN AUGUST/SEPTEMBER 2010 AT A FARM SITE IN SCOTLAND
61
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