According to a report released on Tuesday, the survey, which dubs itself the most complete of its kind, said hundreds of species were found in an area between Florida, Cuba and the Bahamas known as the Florida Straits.
"The fish species that cause the Florida Straits to rank highest in the Atlantic are concentrated on the continental slope, rather than on the continental shelf or in the Caribbean's well-known coral reefs," according to the Centre for Applied Biodiversity Science (CABS) at Conservation International, which conducted the survey.
The study mapped 1172 species in the western Atlantic, and densities in the Florida Straits ranged from 550 to 687, as compared with 413-549 in most western Atlantic coastal waters. In the open Atlantic, the species density ranges from one to 137, according to CABS.
It also said the Greater Caribbean had the Atlantic's greatest concentration of species not found anywhere else, including blind skates and dwarf sharks.
Of the species counted, 227 are endemic to the Caribbean and 11 of those are only found in the Florida Straits, the study said.
Many of the species are considered micro-endemic because their ranges are restricted to very small geographical features, such as isolated island platforms or coastal lagoons.
Micro-endemic species include the dwarf lantern shark, the world's smallest shark which measures about 20 cm.
"Greater Caribbean has the Atlantic's greatest concentration of species not found anywhere else, including blind skates and dwarf sharks"
Those precariously small areas make life there far more delicate than previously thought, the report said.
Most people believe that marine species have large ranges and can just swim their way out of trouble, said Michael Smith, a CABS researcher.
"But we now know that there are hundreds of species in the Florida Straits, and in the broader Caribbean region, with ranges so small that even localised human activities can cause their extinction," he said.
The scientists mapped close to 1200 species of marine fish and other animals in the tropical western Atlantic Ocean. More than 20 percent of the fish species covered by the study are endemic to the Caribbean and nearby seas.