Posted by: marineharvestcanada | July 17, 2009

Sea Floor monitoring always a priority

depomodEvery human activity has an impact so it should be no surprise that both the provincial Ministry of Environment and federal Fisheries and Oceans regulations require our farm sites to do on-going testing that ensures a confined effect under the site and to the surrounding area.

“We welcome the opportunity to monitor our environmental foot-print”, said Greg Gibson, Environmental Assessment Biologist, adding that successful farm site operations depend on a consistently clean and healthy marine environment.

Testing for benthic impact, or the ways in which a farm site affects a specific underwater area, is done on average every 20 to 24 months at each site. This usually happens when the site reaches the maximum amount of fish by weight that it is authorized for just before harvest or just after fish have been transferred away from the site.

The monitoring of the sea floor beneath pen sites is done in one of two ways. Sites that have “soft bottoms” have the sediment samples analyzed for a variety of elements, including copper, zinc, sediment grain size (SGS), total volatile solids (TVS), and sulphides. Sulphides are a by-product of the breakdown of
organic material such as fish feces and can be measured on site.

At rocky “hard bottom” sites, there is no sediment available to test. However, this doesn’t mean they are exempt. Information is gathered at consistent video sample points on transect lines, as for “soft bottom” sites and then compared to video from an unaffected (reference) area. Survey locations are specifically selected to correspond with both the dominant and secondary current directions of each site. The majority of the data comes from collection points at 0 meters, 30 meters as well as the boundary of the tenure to “document a decreasing gradient of effects,” said Greg. The way the Ministry of Environment and Fisheries and Oceans analyze the information is different, depending on their specific regulations, commented Greg. Whether it’s during operation or before fish are introduced to the farm, the sediment samples must not exceed set standards. A site will be fallowed if the results are outside acceptable levels. The sea floor begins to clean up during harvest as the site is emptied of fish. It will be restocked with fish when the sampling results fall within acceptable levels. Our large database shows that sites generally remediate quickly due to improved feeding practices and water currents that effectively disperse organic waste accumulation, added Greg, also commenting that it’s common for sites to never surpass the levels set out for prestocking conditions when the maximum number of fish are on-site. “This allows us the greatest flexibility for our crop planning,” he said.

By Gina Forsyth

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