I'm not sure why anyone would put a high money value on fish caught in the Mediterranean ... it's known as Europe's cesspool. In terms of aesthetics it's a beautiful body of water, what flows into it is another matter entirely.
Interesting factoid about the Med - it has been known to completely evaporate in the past.
Messinian salinity crisis
If the Strait of Gibraltar closes again, which is likely to happen in the near geological future (though extremely distant on a human time scale) (and the Suez Canal closes), the Mediterranean would evaporate dry in about a thousand years.