Examination of about 290 midwater trawl hauls made to a depth of 1000 m in the equatorial and western North Atlantic Ocean from 1961 to 1968 suggests that at least 10 physical boundaries determine the ranges of mesopelagic fishes. The boundaries delimit six pelagic regions----the Slope Water Region, the Northern Sargasso Sea, the Southern Sargasso Sea, the Gulf of Mexico, the Caribbean Sea, and the Amazonian Region----and partly delimit four others----the Eastern Gyre and the Labrador, Lesser Antillean, and Guinean regions....
Backus, Richard H., James E. Craddock, Richard L. Haedrich, and David L. Shores. 1970. "The distribution of mesopelagic fishes in the equatorial and western North Atlantic Ocean." Journal of Marine Research 28, (2). https://elischolar.library.yale.edu/journal_of_marine_research/1181