Friends of Clayoquot Sound: News 060504: Study finds increased levels of mercury in rockfish located near active fish farms

May 4, 2006

Study finds increased levels of mercury in rockfish located near active fish farms

A recent study published on-line in Environmental Science and Technology found elevated levels of mercury in rockfish living near salmon farms, with rockfish in Ahousaht territory found to have the highest mercury levels of fish sampled. Traditional foods such as clams and rockfish are a major component of the diet in many First Nations communities along British Columbia's coastline.

The study concludes prey eaten by rockfish obtained mercury through fish feces and uneaten feed pellets from the seabed beneath the fish farms. It states that concentration of methylmercury in rockfish should not be considered a temporary industry side-effect, unlike depletion of oxygen in the seabed beneath the farms, and increases in invertebrates and bottom-feeding fish.

Celina Tuttle, coordinator of the Wild Salmon and Aquaculture program with the Friends of Clayoquot Sound, welcomes the study and the proactive efforts of First Nations communities to look into issues that potentially can negatively impact the health of people and marine ecosystems. "The steady decline in marine resources and the possible health risks posed by open net pen salmon farming underscores the need for increased research, collaboration and transparency between all stakeholders on issues around the industry," says Tuttle.

Methylmercury is an organic form of mercury, the most toxic form, which bio-accumulates in fish and animals higher up the food chain. It affects the central nervous system and in some cases irreversibly damages areas of the brain. In milder cases of mercury poisoning, adults complain of reductions in motor skills and dulled senses of touch, taste and sight. Although levels of methylmercury in fish sampled did not exceed Health Canada guidelines, the joint First Nations'-academic study cautions that it is unknown how mercury levels will respond to future increases in the number and size of farms, stating that "Aquaculture management plans in all areas should begin to address potential effects on contaminant levels in wild [flora and fauna]."

"There are a lot of unknowns, and positions very polarized," said Tuttle, urging adoption of the Precautionary Principal with respect to management of the salmon farming industry. In summary, the Principal states that where there is some evidence of serious harm final definitive proof should not be necessary before protective action is taken.

Rockfish were sampled in sites exposed to farm wastes and reference sites, isolated from farm waste in terms of current and tide patterns, in the territories of the Ahousaht, Kitasoo/Xaixais and the Musgamagw Tsawataineuk Tribal Council. Sampling was conducted over several visits to each territory in July - December 2004 and October 2005. The study was undertaken in response to concerns of some coastal First Nations communities about safety of traditional foods harvested from the oceans, and to assess the potential of salmon farming to influence food safety.

"These findings have huge implications for coastal communities who supplement their diets with rockfish and other marine foods. We need to pay much more attention to contaminant issues related to fish farms and ongoing monitoring will be an important part of that effort," says Tuttle. The Friends of Clayoquot Sound, a member of the Coastal Alliance for Aquaculture Reform, supports use of closed containment technologies for farming salmon, which greatly reduces the risk of disease and parasite transfer to wild fish, adequate treatment of all waste water, elimination of fish escapes and elimination of use of chemicals or pesticides.

"Ecosystemic Effects of Salmon Farming Increase mercury Contamination in Wild Fish," abstract: http://pubs.acs.org/journals/esthag/index.html. For information about Friends of Clayoquot Sound, Wild Salmon and Aquaculture Program: Celina Tuttle, tel: 250-725-4218, email: celina@focs.ca, www.farmedanddangerous.org

PO Box 489, 331 Neill St., Tofino BC V0R 2Z0
250-725-4218 info@focs.ca