Commercial Shark Pushing in the Caribbean Area 107 



Figure 37 



Family Alopiidae, Threshers. Only five gill openings, the lower 

 ends of the fourth and fifth over the origin of the pectoral fin ; 

 caudal peduncle not expanded sidewise with lateral keels ; two 

 dorsal fins and an anal fin; base of the first dorsal fin does not 

 overlap the pelvics; second dorsal fin much smaller than first; 

 caudal fin about as long as the trunk with a definitely outlined 

 lower lobe ; its axis raised only a little above the main axis of the 

 trunk ; eye without nictitating membrane ; spiracles present. Teeth 

 blad^-like with one cusp. 



Genus Alopias, Threshers. Characters as above. 



Figure 37: Alopias vulpinus, Common Thresher. 



Description: Trunk rather stout; caudal peduncle noticeably 

 flattened sidewise without lateral keels but with a well-marked pit 

 above though there is none below ; snout short and broadly egg- 

 shaped ; gill openings noticeably short, the longest only a little 

 longer than the diameter of the eye; mouth broadly rounded: 

 teeth about 20 on each side in upper jaw and 21 in lower, similar 

 in the two jaws with single cusp, triangular, but with concave 

 outer and convex inner margins and increasingly oblique toward 

 the corners of the mouth ; the third upper tooth (counted from the 

 center of the mouth) only about 1/3 as large as those on either 

 side of it. First dorsal fin with rounded tip, its rear tip far in 

 front of the origin of the pelvics; second dorsal only about 1/8 as 

 long as first; caudal (its most striking feature) occupying approxi- 

 mately 1/2 or more of the total length of the shark, its upper lobe 

 narrow and scythe-shaped, its lower lobe only about 1/8 to 1/9 as 

 long as the upper ; anal similar to second dorsal in size and shape ; 

 pectoral noticeably large, being as long as or even longer than the 

 distance from its origin to the tip of the snout, about 1/2 as broad 

 as long, with rounded tip, deeply concave distal margin and 

 noticeably wide base. 



Color: Back and upper sides varying from bluish or slaty gray 

 to almost black, shading to white below, but with the lower sur- 

 face of the snout and of the pectorals sometimes as dark as the 

 back. The belly is sometimes more or less mottled with gray. 



Size: Born as small as 4 to 5 feet, but probably does not mature 

 until about 14 feet long (including the tail). It commonly grows to 

 16 feet and occasionally to 20 feet. Recorded weight from 300 

 to 320 pounds at 10 feet to about 500 pounds at 14 to 15 feet, with 

 a maximum of perhaps 1,000 pounds. 



Habits: An oceanic species although specimens and especially 

 small ones are often encountered near shore ; feeding chiefly on the 

 smaller schooling fishes of whatever kinds are locally available 

 Bonito, for example, in tropical American waters and also on squi«- 

 Well known for its habit of crowding its prey together by circling 

 the school and lashing the water with its whip-like tail. 



Range: Warm, temperate and subtropical latitudes on both sides 



