I have never heard of blue fish. Its English name is bluefish. It may be the fish you are talking about.

Search for Pomatomus saltatrix on GOOGLE and there will be pictures.

< p>The trevally is also called the flat trevally. The maximum body length is 130 cm.

All oceans except the eastern Pacific. Eastern Atlantic: Portugal to South Africa, including the Mediterranean and Black Seas, Madeira, and the Canary Islands. Western Atlantic Ocean: Canada and Bermuda to Argentina. Indian Ocean: Along the coast of East Africa, Madagascar, southern Oman, southwestern India, the Malay Peninsula and Western Australia. Southwest Pacific: Except for the northern part of Australia, and New Zealand. The Eastern Pacific and the Northwest Pacific do not appear. Almost into the western and central Pacific.

Occur in oceanic and coastal waters. They are most common in clear, productive waters along beach breakers and rocky headlands, although adults can also Found in estuaries and in semi-fresh and brackish waters. Small fish may be found in shallow coastal waters at least 2 meters deep, chasing and attacking small fish in groups. Adults are found in loose schools, often attacking mullet or Schools of other fish and destroying numbers in excess of apparently far ingested food requirements. Eat other fish, crustaceans and cephalopods. Accompanied by sharks and swordfish. A voracious and aggressive species, reporting bites when touched. Swim to warmer waters during summer and to cooler waters during winter. Popular sport fish. Good for eating; mostly sold on the market fresh, also dried or salted, and frozen.