Tuna are safe from being fished to extinction. Eventually the cost of tuna will become so expensive it will cause the Japanese stock market to crash, causing mass suicides by rich Japanese, thus depleting the demand for tuna. /sarc
Well, "Tuna Hell" is about to unfold in Japan.:)
Fishing stocks are crashing everywhere, simply because no one owns the resource. Crashing populations simply means a higher market price, that will essentially mean that fishing will continue until the cost of catching tuna (or whatever fish) exceeds the market price. Meanwhile, the Japanese are getting a great deal that doesn't include anyone's cost for maintaining the resource - viz., the world is subsidizing sushi consumption.
Countries need to get their acts together and start rolling out ITQs (individual transferable quotas), like they use in NZ and AK (for halibut). Otherwise we will just see resources wasted in a free for all to catch fish. This is up for debate in Congress now for US fisheeries generally.