The natural stock of fish and shrimp is not increasing and may be decreasing due to climate change and overfishing, says Ikuo Hirono, a professor with the Tokyo University of Marine Science and Technology.
"Some pollution of the environment" is also to blame, he says.
"We need to do more to protect the environment," he adds.
"It's a big problem.
It's a very serious problem"
A customized collection of grant news from foundations and the federal government from around the Web.
The Charities Aid Foundation has set up a scheme, called the Social Enterprise Assist, that will render interest-free loans of up to £10,000 each to help social enterprise start-ups.