ISTANBUL — Turkey's annual fish production includes 515,000 tons from cultivation and 335,000 tons came from fishing in open waters. In other words, 60% of Turkey's fish currently comes from cultivation, also known as fish farming.

It's a radical shift from just 20 years ago when some 600,000 tons, or 90% of the total output, came from fishing. Now, researchers are warning the current system dominated by fish farming is ultimately unsustainable in the country with 8,333 kilometers (5,177 miles) long.

Professor Mustafa Sarı from the Maritime Studies Faculty of Bandırma 17 Eylül University believes urgent action is needed: “Why were we getting 600,000 tons of fish from the seas in the 2000’s and only 300,000 now? Where did the other 300,000 tons of fish go?”

Professor Sarı is challenging the argument from certain sectors of the industry that cultivation is the more sustainable approach. “Now we are feeding the fish that we cultivate at the farms with the fish that we catch from nature," he explained. "The fish types that we cultivate at the farms are sea bass, sea bram, trout and salmon, which are fed with artificial feed produced at fish-feed factories. All of these fish-feeds must have a significant amount of fish flour and fish oil in them.”

That fish flour and fish oil inevitably must come from the sea. "We have to get them from natural sources. We need to catch 5.7 kilogram of fish from the seas in order to cultivate a sea bream of 1 kg," Sarı said. "Therefore, we are feeding the fish to the fish. We cannot cultivate fish at the farms if the fish in nature becomes extinct. The natural fish need to be protected. The consequences would be severe if the current policy is continued.”