NATURAL HISTORY OF THE SANDBAR SHARK 



Anicrii'u. Altlioufih milherti may be in compi'li- 

 tioii with other species of Euhimia for food in 

 some parts of its range, it does not compete with 

 otlier si)ecies of Enlam'ia for nursery grounds. 



Of the other carcharhinids of the northwestern 

 Atlantic, the genera Prionace and Pterulamiops 

 are pelagic surface dwellers; Hypoprion is con- 

 fined to waters generally deeper than 100 fathoms 

 near shelves or banks; Negapnon, Apriondon, 

 ScoUodon, and Carchcirhinus are shallow water 

 sharks that spend at least some part of their lives 

 in shallow lagoons, river mouths, or estuaries, 

 and venture into deeper water rarely except for 

 transitory movements; the species of Eulamia are 

 sharks of the continental shelves, oceanic banks, 

 and island terraces, although some species extend 

 their langes well insliore and also for consider- 

 able distances beyond the limits of the Conti- 

 nental Sjielf. The only other western North At- 

 lantic carcharliinid genus, Galeocerdo^ is repre- 

 sented by a single species in subtropical and 

 ti'opical waters out to depths of at least 200 

 fathoms. It does not exhibit the specialized 

 schooling habits of the other carcharhinids. shows 

 no strong migratory tendencies, and is less re- 

 stricted in habitat choice than the others. There 

 seems to be a tendency to greater variation in the 

 number of young produced as well as a greater 

 number per litter in Galeocerdo and Prionance 

 and possibly also in Pterolamiops than in other 

 northwestern Atlantic carcharhinids. Insofar as 

 is known, there are no very important differences 

 in the general outlines of the life history patterns 

 of Necjapncm^ Apnonodon. Scoliodon, Carchar- 

 himif!, and EitJamia, although there appear to be 

 many differences in detail. 



Barriers which may restrict the movements of 

 the larger sharks including Eulamia mUherti are 

 not i-eadily apparent. Occasional captures of 

 sharks outside areas of normal concentration of 

 the species prove that they can and do wander. 

 The remarkable thing is that large sharks tend to 

 remain within definable iial)itats and geographi- 

 cal ranges. 



Since species of EuJnnna are, in general, less 

 dependent on land masses than Carcharhimis and 

 extend their activities regularly to surface waters 

 of the open ocean beyond the Continental Shelf. 

 it would not be surprising to find that some 

 species have a very wide distribution in temperate 



55250S 0—60 -2 



and tropical seas. Euhimia fiaridana (Bigelow, 

 Scliroeder, and Springer) ma}' be an example of 

 such a distribution (see Strasburg, 1958). Those 

 species of Eulamia, such as milherti, which are 

 tied to shallow-water habitats are presumably 

 subject to a greater degree of isolation. 



SPECIMENS EXAMINED 



Specimens, records, and field observations for 

 this report have been assembled over a period of 

 about 25 years during which time I have exam- 

 ined several thousand sandbar sharks. Available 

 records of the commercial shark fishery cover 

 more than 100.000 adult Eulamia milberti. About 

 half of these sharks were measured at the point 

 of landing. Earlier records of the stations in- 

 cluded specimens of Eulamia altima and Eulamia 

 foridana under the heading sandbar sharks. 

 Since I visited most of the stations frequently, 

 and during part of the period between 1935 and 

 1950 supervised recording procedures, I saw rela- 

 tively large numbers of sandbar sharks. Speci- 

 mens which appeared unusual to station employ- 

 ees were retained when practicable for my inspec- 

 tion. ]\Iost of my observations were made along 

 the coasts of southern Florida. Adequate num- 

 bers of specimens for some purposes have been 

 examined from the eastern and northern parts of 

 the Gulf of Mexico, the Atlantic coast of the 

 United States south of Cape Cod, and from the 

 Caribbean coast of Nicaragua and Costa Rica. 

 The available material in several museum col- 

 lections in the United States was studied, but this 

 consisted chiefly of preserved embryos or very 

 young sharks and dried jaws. 



The collection of data in the shark fisheiT suf- 

 fered from interruptions and was assembled to 

 aid an industrial operation rather than for a 

 biological study. The difficulty in handling speci- 

 mens, averaging nearly 7 feet in length as adults 

 with an average weight of about 135 pounds, has 

 made it necessary to select different series or 

 samples for diffei'ent objectives: one sample for 

 length-weight relations; another for tooth counts, 

 and so on. 



1 was unable to find spirit-jireserved specimens 

 of eastern Atlantic or Mediterranean origin re- 

 ferable to either E. plumbeus or E. milberti dur- 

 ing a hasty examination of catalogs and specimens 

 at the Museum d'llistorie Naturelle in Paris or in 



