FRØYA, Norway—Salmon farmers, swimming in profits, are looking for better ways to raise their fish.

Amid growing global demand for food, aquaculture companies aim to be bigger players by investing in new feeding processes and betting on elaborate new farming techniques. By 2016, for instance, SalMar ASA—one of the world's largest salmon producers—will launch a pricey and largely untested offshore fishing platform designed by a longtime oil executive.

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