In Morton v
Canada (Fisheries and Oceans), 2015 FC 575, the Federal court
put unusually strong reliance on the precautionary principle to
strike down parts of an aquaculture licence granted by the Minister of Fisheries and Oceans (the
"Minister") to Marine Harvest, a multinational seafood
Marine Harvest operated a fish farm in Shelter Bay, BC, not far from the wild Pacific salmon migration route along the Fraser River. In March, 2013, the company transferred infected Atlantic salmon from one of its hatcheries to Shelter Bay. The Fisheries Act aquaculture licence allowed them to do it, because both the hatchery and the fish farm were within the same "Salmonid Transfer Zone".
Alexandra Morton, a noted biologist, launched a court challenge against the Minister and Marine Harvest in Federal Court. Ms. Morton successfully argued that allowing this movement of infected smolts conflicted with the overriding requirements of the Fishery (General) Regulations, SOR/93-53 (FGRs), which prohibit fish transfers that may adversely affect wild fish or harm their protection and conservation.
The 2012 Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River concluded that there is some risk posed to wild sockeye salmon from diseases on fish farms. It recommended that ensuring the health of wild stocks should be "DFO's number one priority in conducting fish health work" (Cohen Commission, The Uncertain Future of Fraser River Sockeye, vol 2 at 113 and vol 1 at 474).
The Minister argued that that the court should be highly
deferential to his department's expertise on complex matters of
fisheries science. Since he was satisfied that the virus in the
infected smolts had not been proven to cause disease in wild
Pacific salmon, his decision must be presumed to be reasonable
unless Ms. Morton could prove otherwise.
Fortunately, the Court disagreed.
Under the precautionary principle, a lack of full scientific certainty (in this case, how harmful the virus is to wild Pacific salmon) does not excuse lax regulation. Allowing the transfer of infected fish into open pens near the wild fish run did not err on the side of caution, and did not reflect the precautionary principle.
 The evidence before the Court demonstrates that there is a body of credible scientific study, conducted by respected scientists in different countries, establishing a causal relationship between PRV [the virus] and HSMI [the disease]. The evidence also indicates that there are scientists who question the link – but concede that no other disease agent has been identified as the culprit for HSMI. ... Thus, although there is a healthy debate between respected scientists on the issue, the evidence suggests that the disease agent (PRV) may be harmful to the protection and conservation of fish, and therefore a "lack of full scientific certainty should not be used a reason for postponing measures to prevent environmental degradation".
The Federal Court accepted the precautionary principle as a norm of substantive Canadian law, to be used in the interpretation of all statutes and regulations. The Marine Harvest license conditions were invalid, and conflicted with section 56 of the FGRs, both as a matter of general statutory interpretation and because the FGRs must be interpreted through the lens of the precautionary principle:
 The precautionary principle recognizes, that as a matter of
sound public policy the lack of complete scientific certainty
should not be used as a basis for avoiding or postponing measures
to protect the environment, as there are inherent limits in being
able to predict environmental harm. Moving from the realm public
policy to the law, the precautionary principle is at a minimum, an
established aspect of statutory interpretation, and arguably, has
crystallized into a norm of customary international law and
substantive domestic law...
 The consequence of interpreting subsection 56(b) consistently with the precautionary principle is that the licence conditions must also reflect the precautionary principle. As the licence conditions cannot derogate from or be inconsistent with subsection 56(b), they therefore cannot derogate from the precautionary principle.
This may be the strongest, most nuanced judicial statement on the precautionary principle in Canada since the Supreme Court of Canada first recognized it in 114957 Canada Ltée (Spraytech, Société d'arrosage) v Hudson (Town), 2001 SCC 40.
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