By Gina Forsyth
“In the absence of an equivalent Canadian Standard, Marine Harvest Canada has voluntarily committed to apply the stringent Norwegian standards for marine farm sites,” said Matt Clarke, Marine Engineering Manager. Working with Norwegian company Aqualine, based in Trondheim, Marine Harvest is taking advantage of the growing body of scientific knowledge that is leading to continual improvement, an essential component to even more successful farming practices. Marine Harvest has embraced NS9415 – the Norwegian Standard on Marine Fish Farms, which was developed by Standards Norway and adopted by the Norwegian Government as law.
With industry design approaches evolving with experience, the company is moving away from rigid steel pen systems and embracing flexible plastic circles, which are reinforced with steel for strength. Each pen moves independently of one another, resulting in less tension and stress on the entire system. “In the past, we’d batten down the hatches on sites when poor weather was on its way, but now we’re rolling with nature’s punches. The technology afforded by plastic cage systems allows the farm to move in response to dynamic loading.”
In the past the science of wind, waves, and current and their effects on pen systems weren’t considered as essential as they are today. Now however, the importance of distributing the load (or force) of these environmental factors evenly across each pen is an engineering priority for both staff safety and the security of the fish.
Although more robust cage infrastructure is important, it’s only part of the picture. “We’re continuing to improve our collection of site
Computer models help estimate loading on anchors and ropes. This example shows the stressors should an anchor line break (middle right side). Loading is shown in tonnes.
data to provide us with accurate information so we can make the appropriate decisions. “We have to make sure that our anchoring simulations accurately account for each site’s unique location and weather conditions.” Using inaccurate simulations can lead to poor designs and increased problems, explains Matt.
Another step forward has been in the area of anchors. Concrete blocks used as dead-weight anchors have long been used in BC’s marine industries. However, it is very hard to predict how much holding power a concrete block will provide. Instead, mechanical plough anchors shaped like large hooks are becoming the standard choice. These anchors are sturdier and should they shift even slightly, they have the ability to re-hook themselves into the site bottom. “This approach allows us to have more confidence in our anchors” said Matt.
Fish grow more successfully in water with higher oxygen levels; these naturally exist in less protected areas. Working to the Norwegian standards of anchoring and cage design also increases the options for new site locations. Exposed areas, where wind, wave, and water currents are particularly high-energy, can now be more seriously considered. By conducting a thorough engineering analysis that takes into account the actual environmental conditions of an area, we can make informed decisions on what sites to choose and how to anchor them.
