Stores stocked seafood from MSC-certified fisheries for fear of criticism from environmental campaign groups if they did not do so, said Martin Jassa, an analyst at strategic planners Callander McDowell.
Research had shown sustainability to be low on seafood shoppers' lists of priorities, he claimed.
The increase in the number of fisheries applying for MSC certification was a reflection of the increased commitment of supermarkets to the scheme, Jassa added.
However, the MSC claimed its own research showed consumer recognition of the MSC logo had increased from 9% to 12% over the past 12 months.
"Consumers are increasingly responsive to the role that they can play in rewarding good practice," said an MSC spokesman.