146 Commercial Shark Fishing in the Caribbean Area 



Figure 55 



Family Dalatiidae. Resembling the Squalidae, except that there 

 are no dorsal fin spines. 



Genus Isistius. The rear end of the base of the first dorsal is 

 over the origin of the pelvics or behind them ; the interspace be- 

 tween the first and second dorsal is shorter than that between 

 the second dorsal and the caudal. 



Figure 55. Isistius brasiliensis, Luminous Shark. 



Description: Among the West Indian sharks of the ordinary 

 body form that lack an anal fin, this species is set apart by the 

 facts that it lias no fin spines, its first dorsal stands so far back that 

 the rear end of its base is about over the point of origin of its pelvics, 

 its lower teeth are symmetrical and triangular, the uppers being thorn- 

 like and widely spaced, and its color pattern is unusually striking, (see 

 below) 



Color: Dark brown above and paler brown below with a con- 

 spicuous dark collar around the neck in the region of the gill 

 openings. The lower surface (except for this collar) is thickly 

 sprinkled with black dots. 



Size: Females are mature at a length of 18 inches and recorded 

 specimens have ranged in length up to 19^ inches. 



Habits: This is an oceanic species; most of them so far taken 

 have been caught at small depths or at the surface at night. Noth- 

 ing is known of its diet or breeding habits. It is mentioned here 

 because it is remarkable for being brilliantly phosphorescent, the 

 entire lower surface (except the dark collar) emitting a vivid green- 

 ish light at times. 



Range: Widely dispersed in the tropical and subtropical belts 

 of all three oceans though it does not seem to be common any- 

 where. In the western Atlantic it has been taken off Rio de 

 Janeiro, among the Bahamas and north of them. 



