The Finetooth Shark is a species of requiem shark, family Carcharhinidae. Valued for its meat, the finetooth shark forms an important component of the commercial gillnet shark fishery operating off the southeastern United States. Population assessments suggest that this fishery does not currently pose a threat to U.S. populations of the species. The International Union for Conservation of Nature (IUCN) has therefore listed the finetooth shark under Least Concern, though there is no fishery data available for this species off South America. This shark is not known to pose a danger to humans, though it snaps vigorously when captured and should be handled with caution.
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. There are 12–15 tooth rows 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. There is no ridge running between the dorsal fins. The pectoral fins are small and falcate (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.
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.
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 eat 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.