Shares of Norwegian salmon farming companies on the Oslo Stock Exchange didn't react favorably to mid-day news that Canadian Prime Minister Justin Trudeau's Liberal Party platform includes a vow to transition all netpen salmon farms in British Columbia to closed-containment systems.

Shares of all major listed companies plunged as markets opened, with Grieg and Mowi -- the two listed companies with operations in British Columbia -- falling the sharpest.

Mowi's dip came early, hitting a low of NOK 204 (€20.40/$22.40) per share -- down 2.3 percent from its opening high. Grieg followed suit, with its shares reaching a low of NOK 107.80 (€10.80/$11.90) before recovering to a close of NOK 109.70 (€11/$12.10).

By the end of the day, Norway Royal Salmon, Salmar and Leroy had recovered, while Grieg and Mowi remained down by 1.35 percent and 1.33 percent, respectively.

Industry reaction to the proposed move was swift, with reactions ranging from "unachievable," to "nonsense" to "shameful."

A day of bad news for salmon farming companies. Photo: IntraFish