NATURAL HISTORY OF THE SANDBAR SHARK 



13 



Whatever the particular reason or reasons may 

 be, the general absence of young milberti in the 

 Gulf of Mexico shows that conditions are un- 

 favorable for them. Circumstantial evidence 

 suggests that interspecies competition is respon- 

 sible, because large C. leucas eat young milberti. 

 No explanation is apparent for the common 

 occurrence of E. milberti along the continental 

 shores and its absence from most of the West 

 Indian shallow waters except that the species 

 seems to have preferences for certain types of 

 bottom. E. ??ulberti is ordinarily not common in 

 areas of coral reefs or where the bottom is rough. 

 Since it is chiefly a bottom-dwelling species, it is 

 not surprising that it would exhibit preference 

 for one type of bottom over another. In its 

 migratory passages around the southern tip of 

 Florida and the Florida Keys, however, there 

 appears to be active avoidance of the fringing 

 reef. Here the migrating adults leave the rela- 

 tively shallow areas they inhabit on both the east 

 and west coasts of Florida and temporarily enter 

 , and feed in much deeper water. J ■©» ^ ' 



Nursery grounds and distribution of young '•^*  



I The principal nursery grounds of the western 

 ' North Atlantic population of Eulami.a milberti 

 lie in relatively shallow water along the Atlantic 

 coast of the United States from Long Island to 

 Cape Canaveral, Fla. This range may be ex- 

 tended slightly at its northern end to the south 

 side of Cape Cod in favorable years but the 

 southern limit is more definitely fixed. Not one 

 young milberti has been taken south of Cape 

 Canaveral, around the tip of Florida, or in the 

 eastern Gulf of Mexico. On the east coast of 

 Florida, south of Cape Canaveral, a few sexually 

 immature milberti of almost adult size have been 

 taken; but in this area adult milberti are com- 

 mon. A great quantity and variety of fishing 

 effort lias been concentrated south of Cape 

 Canaveral on the Florida coast. The total ab- 

 sence of young milberti here is remarkable in 

 view of the somewhat indefinite range limits of 

 the adults. 



A secondary nurseiy range apparently lies in 

 the northwestern part of the Gulf of Mexico. It 

 is indicated only by the capture of a few females 

 with near full-term embryos near the mouth of 

 the Mississippi River, the capture of a large 



552508 — 60 3 



milberti with nearly full-term embryos off the 

 Texas coast (Henry Hildebrand, 1954), and a 

 specimen 747 mm. (nearly 30 inches) from the 

 Texas coast (Bigelow and Schroeder, 1948). 



It is probable that gravid females wandering 

 away from the principal range of the species give 

 birth to young along the Mexican and Central 

 American coast, but no records of the capture of 

 young in this area have been found. Shark fish- 

 ing on a small scale has been carried out over 

 most of this area and catches have been examined 

 at various points from the mouth of the Rio 

 Grande River to Costa Rica; but excepting the 

 Gulf of Campeche, no young milberti appeared. 



The female Eulumia milberti^ which move into 

 the principal nur.sery areas to give birth to their 

 young, do not remain there long and do not feed 

 actively while there. This may explain the 

 scarcity of records of captures of adult E. m,il- 

 bertl along the Atlantic coast. Great South Bay, 

 Long Island, is one of the nursery areas of E. 

 milbei-tiand accounts of the appearance of fe- 

 males in the bay and birth of the young are given 

 by Thome (1916). Additional mention of the 

 appearance of E. milberti in the Great South 

 Bay area is made by Nichols (1918), who notes 

 that the interesting fact about them is that the 

 adults of the two sexes of the same species are 

 almost never taken together near Long Island. 

 Here the adult females are E. milberti and the 

 adult males are Carcharhinus leu<:as. 



Records of young sharks from Chesapeake Bay 

 show that E. milberti gives birth to young in the 

 bay in summer. William Massmann, of the Vir- 

 ginia Fisheries Laborator}^ has kindly given me 

 (in correspendenc*-) records of E. milberti from 

 the lower Chesapeake Bay. He sa5's — 



Although young of this species are probably the most 

 abundant shark In the Bay In summer, I would not say 

 that It is numerous. • • • it is commonly caught by 

 anglers and probably rather generally distributed in the 

 lower Bay. I have not seen an adult in the Bay or any 

 individual more than three and a half feet long. 



After a comparatively brief period in shallow 

 water or in the mouths of bays, perhaps at the 

 beginning of cool weather, young vrllbertl appear 

 to move offshore. Tlie only area from which 

 young milberti are known in the winter .season 

 lies off the coasts of tiie Carolinas at depths out 

 to 75 fathoms. 



->( 



