This is partly a question of sustainability. Frozen tuna is “far more ecological than air-freighted fresh tuna,” Jean-Luc Meklemberg, who heads Comptoirs Oceaniques’ site in Boulogne-sur-mer, northern France, said.

It's also about quality. Comptoirs Oceaniques, which sells under the 'Fish Is Life' brand, only buys tuna frozen at minus 60 degrees. “It’s the only one that guarantees the quality,” Meklemberg said.

It also fits within the group’s aim to increase its sales to the retail segment, he said.

“We work more and more with the retail segment such as Metro Cash & Carry and wholesalers.