Rhizoprionodon porosus

Author: (Poey, 1861)

Field Marks:
See key to species and diagnostic features.

Diagnostic Features:
Prenarial snout 3.3 to 4.5% of total length; upper labial furrows short, 1.3 to 2.3% of total length; total count of enlarged hyomandibular pores on both sides of head just behind mouth angle usually over 17 (9 to 19 on each side); teeth with serrations in adults; dentitions not differentiated between the sexes; total tooth rows usually 25/24. First dorsal origin usually over or slightly behind pectoral free rear tips; second dorsal origin ranging from above anal midbase to over rear fourth of its base; pectoral anterior margin usually longer than first dorsal length from origin to free rear tip; adpressed pectoral apex reaching behind first third of first dorsal base. Posterior monospondylous precaudal centra moderately enlarged; precaudal centra less numerous than caudals, precaudals 66 to 75, total counts 136 to 159. Size moderate, males maturing at over 58 cm total length. Colour brown or grey-brown above, white below, sometimes with white spots on sides and white-edged fins.

Geographical Distribution:
Western Atlantic: Bahamas, Cuba, Jamaica, Hispanola, Puerto Rico, Virgin Islands, Martinique, Honduras, Panama, Venezuela, Brazil, Uruguay.

Habitat and Biology:
An abundant tropical littoral shark, usually found close inshore on the continental and insular shelves of the Caribbean and South America, but also found in offshore waters down to 500 m depth; one was caught near the surface in water 6036 m deep, well offshore, but this is exceptional.

Viviparous, with a yolk-sac placenta; number of young 2 to 6. Gestation period about 10 to 11 months; gives birth in the spring or early summer off southern Brazil.

Mostly eats small bony fishes, including wrasses, but also marine snails, squid and shrimp.

Size:
Maximum about 110 cm, males maturing at about 60 cm and reaching at least 85 cm, females maturing at about 80 cm and reaching at least 108 cm; size at birth about 31 to 39 cm.

Interest to Fisheries:
One of the commonest, if not the most common, inshore sharks where it occurs, and a regular object of artisanal and commercial fisheries. It is caught mainly with floating longlines but also bottom trawls (especially shrimp trawls), trammelnets, and probably hook-and-line. It is used salted or frozen for human consumption and processed into fishmeal.

Remarks:
It is uncertain whether this Caribbean, Central and South American species is separable from the northern R. terraenovae which is allopatric to it, or instead represents a southern and Caribbean subspecies of terraenovae or a clinal variant of it. Springer (1964) gives reasons for recognizing the species, which are tentatively followed here pending detailed studies of the terranovae-porosus group of Rhizoprionodon along the coasts of Central and South America.

Type material:
Holotype: Unknown, 815 mm male (presumably adult) mentioned. Type Locality. Cuba.

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