big fish

もしカジノが日本で合法化されたなら、どのような影響がでるのでしょうか。

Casino giants are eying Japan for its next big gaming market

The emergence of Macau as the world's largest gaming market has led the industry to wonder what untapped markets there are around the world, particularly in Asia.

The Philippines, Korea, and Singapore are a few countries that have opened up gaming, to varying levels of success, but the big fish that's still outstanding is Japan.

Not only is Japan the world's third-largest economy, but it's a place where casino gambling is illegal.

But that may be changing and casino giants like MGM Resorts, Las Vegas Sands, and Wynn Resorts already have their eye on the market.

The vast opportunity for casinos in Japan

Japan has been toying with the idea of allowing casinos for years. In 2014, it appeared the country would soon allow a small number of very large casino resorts, but the bill never passed. But slowly the political will is growing to allow gaming in the country.

New speculation emerged Monday that gaming may be near after MGM Resorts CEO James Murren said his company was willing to spend $4.8 billion to $9.5 billion on an integrated resort in Japan. In past years, Las Vegas Sands CEO Sheldon Adelson and Steve Wynn have said they would be willing to spend as much as $10 billion to build in the country as well.

（以下省略）

http://www.businessinsider.com/casino-giants-japan-next-big-gaming-market-2016-11

今回取り上げる表現は、big fishです。

Oxford Dictionary of English (Second Edition Reserved, Oxford University Press)によると、 “a big fish”で “an important or influential person”とのことでした。
また “a big fish in a small pond”の形で “a person who is important only within the limited scope of a small field or group”と載っておりました。

Oxford IDIOMS Dictionary for learners of English (Second edition, Oxford University Press)で調べたところ “a big fish”または “a big fish in a little/small pond”の形で、 “an important person but only in a small community, group, etc”と記載されておりました。

今回の記事では、 “the big fish that's still outstanding is Japan.”と使用されております。「日本で合法化すれば必ず成功する」といったニュアンスを含んでいるように思います。（Gomez）