The Marine Stewardship Council will not be including aquaculture in its certification and labelling programme for the foreseeable future.
With 45% of the world's fish supplies currently coming from fish farms, the MSC's Board of Trustees moved last week to clarify its position.
"It is the board's belief that accelerating the delivery of the MSC's existing programme of certifying wild capture fisheries must remain the priority for its work," the MSC said.
"We are helping to create a market for sustainable wild-caught fish that is serving as an incentive for more and more fisheries to seek independent third-party certification."
A spokesman added that the MSC was not taking a "philosophical position" - it simply did not have the resources to expand into aquaculture at the present time, though it did not rule it out in future.
Young's Seafood has developed its own Fish for Life sustainable standard to allow it to monitor fisheries not covered by the MSC.