Fishes of the Western North Atlantic 413 



Indeed, it often moves in on the flood tide over flats tliat are laid bare on the ebb, 

 withdrawing again as the tide falls. ''^ The greatest distance out from the coast where 

 G. micrura has been recorded definitely*' is about 2 2 miles. 



Since G. micrura occurs commonly along the northern coast of South America and 

 has been definitely recorded from water as warm as 29.5-30° C (85-86° F) in the Gulf 

 of Mexico off Texas, it is at home in the highest of tropical sea temperatures. The 

 seasonal limits of its presence in Chesapeake Bay (May to late November, p. 413) sug- 

 gest that its vernal dispersal northward along the United States Coast and its autumnal 

 withdrawal roughly coincide with the corresponding shifts of the isotherm for about 

 15— 16° C (59— 60° F). G. micrura has not been reported from fresh water, but its 

 presence in estuarine situations in French Guiana and Florida (Indian River) suggests 

 that it may occur in brackish water. On the other hand, it has been reported from water 

 of full oceanic salinity." 



Presumably G. micrura is a year-round resident in tropical South American waters, 

 in the West Indian region, and as far north as southern Florida. It has long been known, 

 however, that it visits the immediate shore waters of North Carolina only during the 

 warmer part of the year,*^ although its recent capture off Cape Lookout in February 

 shows that some may winter that far north, offshore. In Chesapeake Bay it is taken 

 from May until November, our latest date for it there being November 28.*' The few 

 captures from farther north for which definite dates are recorded have been limited 

 to the months of July,'" August," and September." 



The Lesser Butterfly Rays that visit the Middle Atlantic Coast of the United 

 States are known to produce young from late May through July and into August,'* 

 and they may do so still later in the season for all that is known to the contrary. In 

 the tropical parts of its range, where the water temperature changes but little from 

 season to season, newborn G. micrura may be expected throughout the year. 



Numerical Abundance. See Details of Occurrence., p. 414. 



Relation to Man. It is sometimes used for human food in French Guiana and per- 

 haps in other tropical localities; and its wings are used to a limited extent as bait by the 

 crab fishery in Chesapeake Bay. It is perfectly harmless, since it lacks a tail spine. 



Range. Coastal waters of the tropical warm-temperate belt of the western Atlantic 

 from Brazil to Chesapeake Bay and outer coast of Maryland, northward occasionally 

 to New York and to southern New England (Woods Hole); it is also listed for tropical 



65. A Butterfly Ray has been recorded (Manter, Yearb. Carneg. Instn., 31, 1932: 288, as Pteroplatea maclura) from 

 60 fathoms off the Tortugas, Florida. But there is no way of knowing whether it was G. micrura or G. altauela. 



66. Two specimens, 740 and 780 mm wide, were trawled by the U. S. Fish and Wildlife Service vessel Albatross III 

 off Cape Lookout, North Carolina, in Lat. 34°24' N, Long. 76°04' W, at a depth of 24 fathoms, February 19, 1950; 

 bottom temperature 20.7° C (69.2° F). 



67. 36.5-36.7 "/do, in the Gulf of Mexico off Aransas Pass, Texas (Gunter, Publ. Inst. mar. Sci. Texas, i [i], 1945: 23). 



68. Data as to dates of arrival and departure for North Carolina waters are lacking. 



69. Hildebrand and Schroeder, Bull. U.S. Bur. Fish., 43, 1928: 68. 



70. Sandy Hook Bay, New Jersey; Narragansett Bay, Rhode Island; Woods Hole region, Massachusetts. 



71. Ocean City, Maryland; Sandy Hook Bay, New Jersey; Buzzards Bay, Massachusetts. 



72. Buzzards Bay; Massachusetts. 



73. Recorded dates are May 27, July 27, and August 11 for North Carolina; July 24 in Chesapeake Bay. 



