136 Commercial Shark Fishing in the Caribbean Area 



Figure 50 



Family Sphrynidae, Hammerhead Sharks. 



Figure 50. Sphyrna diplana, Hammerhead. 



Description: Trunk strongly flattened sideways; head with a 

 slight but noticeable indentation in front in the mid-line (there is 

 no indentation in Sphyrna zygaena); the front margin of the head 

 is also scalloped with a deep rounded depression opposite each 

 nostril ; the distance from the nostril to the eye is about as long 

 as the diameter of eye (only about 1/2 that long in zygaena); the 

 corners of the mouth are well in front of the outer rear corners of 

 the head or "hammer"; a line connecting outer ends of nostrils 

 passes a little in front of the mouth; eye nearly circular, its dia- 

 meter about 1/3 as long as head in front of mouth; first gill open- 

 ing a little more than 1-1/2 as long as diameter of eye, the fifth 

 gill opening being above the origin of the pectoral fin; there are 

 15 or 16 teeth on each side of the upper and lower jaws and usually 

 one or two very small ones in the center of the jaws ; the teeth 

 are triangular in shape on expanded bases and the cusps are 

 smooth edged (serrated in Sphyrna tudes) ; the first tooth from the 

 center of jaw is much smaller than the second, and the fifteenth and 

 sixteenth at the corners of the mouth are very small indeed. The free 

 rear tip of the second dorsal is much longer than its vertical 

 height and at least as long as the front margin of the fin; pelvic 

 fins have nearly straight margins and rear margin of anal is deeply 

 concave. 



Color: Light gray above, shading to white below; the pectorals 

 tipped with black on their underneath surfaces. 



Size: A moderately large shark; young are about 16 inches 

 long when born and grow to a length of about 8 feet and probably 

 longer. 



Habits: As this species had been confused with its close relative. 

 Sphyrna zygaena, until recently, there is little known specifically of 

 its habits. It is probable, however, that they are very similar to 

 the latter. (Figure 49.) 



Range: Tropical and warm temperature Atlantic, probably also 

 in the Mediterranean. It is known from Rio de Janeiro, Gulf of 

 Mexico and as far north as Delaware. Because of past confusion 

 with Sphyrna zygaena little is known of its abundance and distribution 

 in the Caribbean region, but it very probably is more or less common 

 there. 



