Finetooth Shark

The body of the finetooth shark is slender and streamlined. The snout is long and pointed, with the nares preceded by short, broadly triangular flaps of skin. The eyes are large and round, with nictitating membranes (protective third eyelids). The mouth is broad with well-defined furrows at the corners. Twelve to 15 tooth rows occur on either side of the upper jaw and 13–14 tooth rows on either side of the lower jaw. Each tooth is small and needle-like, with a narrow central cusp and smooth to minutely serrated edges. The five pairs of gill slits are long, measuring about half the length of the dorsal fin base. The first dorsal fin is high and triangular with a pointed apex, originating forward of the free rear tips of the pectoral fins. The second dorsal fin is relatively large and originates over the anal fin. No ridge runs between the dorsal fins. The pectoral fins are small and sickle-shaped, with pointed tips. The dermal denticles are small and overlapping, each bearing three horizontal ridges leading to marginal teeth. Living finetooth sharks are a distinctive dark bluish-gray above and white below, with a faint pale stripe on the flanks and no prominent fin markings. Some individuals from Florida have green eyes. Males average 1.6 m (5.2 ft) in length and females 1.7 m (5.4 ft); the largest shark on record was 1.9 m (6.2 ft) long.

In North American waters, the finetooth shark is common and found from North Carolina to the northern Gulf of Mexico, and very occasionally straying as far north as New York. In Central and South American waters, it is rare, but may occur more widely than presently known, having been reported off Trinidad and Guyana, infrequently from the Caribbean Sea, and off southern Brazil from São Paulo to Santa Catarina. The northwestern Atlantic, Gulf of Mexico, and South America populations are distinct, with little interchange between them. Old records exist of this species in the eastern Atlantic off Senegal and Guinea-Bissau, but these likely represent misidentifications of spinner sharks (C. brevipinna). The finetooth shark is often found near beaches and in bays and estuaries. It inhabits extremely shallow waters, no deeper than 10 m (33 ft) in the summer and 20 m (66 ft) deep in the winter. Historically, it was known to venture into rivers in the Gulf Coastal Plain of Texas, though most of paths into this area are now blocked by dams. The northwestern Atlantic population of this species is strongly migratory: juveniles, followed by adults, arrive off South Carolina from late March to early May, when the water temperature rises above 20 °C (68 °F). They remain until September to mid-October, until the water temperature drops and they move south to Florida. …

Adult and juvenile finetooth sharks form large schools. This energetic, fast-moving predator feeds mainly on small bony fishes, often entering the surf zone during the day to hunt. The most important prey of this species in the northwestern Atlantic is the Atlantic menhaden (Brevoortia tyrannus), with sharks of all ages off northwestern Florida eating almost nothing else. The menhaden are swallowed whole after the head has been removed. Other known prey species include spot croaker (Leiostomus xanthurus), Spanish mackerel (Scomberomorus maculatus), mullet (Mugil spp.), shrimp, and in one case a juvenile Atlantic sharpnose shark (Rhizoprionodon terraenovae), which may have been scavenged from the bycatch discard of a shrimp trawler. The finetooth shark may be preyed upon by larger sharks. Parasites documented from this species include the tapeworm Triloculatum geeceearelensis, and unidentified species in the genera Anthobothrium, Paraorygmatobothrium, and Phoreiobothrium.

Life history. Like other requiem sharks, the finetooth shark is viviparous: the developing embryos are nourished by yolk for the first 15 weeks, after which the depleted yolk sac develops into a placental connection to the mother. Females produce litters of two to six pups every other year. …