Blacknose Shark, Carcharhinus acnonotus
Blacknose Shark, Carcharhinus acnonotus. Fish caught from coastal waters off Sebastian, Florida, April 2021. Length: 79 cm (2 feet 7 inches). Catch, photograph and identification courtesy of Ben Cantrell, Sebastian, Florida.
The Blacknose Shark, Carcharhinus acnonotus, is a member of the Requiem Shark or Carcharhinidae Family, and in Mexico as tiburón canguay. Globally, there are thirty-five species in the genus Carcharhinus, of which seventeen are found in Mexican waters, seven in the Atlantic, four in the Pacific, and six in both the Atlantic and Pacific Oceans.
The Blacknose Shark has a slender, streamlined body. They have a noteworthy well-developed skin-flap in front of each nostril. They are pale green to yellow-gray in dorsally transitioning to white ventrally with black tips under the tip of the snout (for which they are named and is less prominent in mature animals), the second dorsal fin and the upper caudal lobe. The anal fin is deeply notched; their caudal fin is strongly asymmetrical with a well-developed lower lobe; their first dorsal fin originates over the rear tips of the pectoral fins and is small and sickle shaped with a pointed apex and a short, free, rear tip of the pectoral fins; their second dorsal fin originates over or slightly before the anal fin origin and is relatively large and less than half the height of the first; and their pectoral fins are short and tapered. Their head is with a long with a rounded snout and large eyes with a mouth that is equipped with 12 to 13 triangular oblique teeth that have serrated edges on the upper jaw and 11 to 12 on the lower jaws with one or two symphysial teeth found in the middle. They have five pairs of short gill slits that are less than one third of the dorsal fin base. They do not have an interdorsal ridge (a key to the identification). Their body is covered with dermal denticles.
The Blacknose Shark are found within reefs near the continental and insular shelfs in and coastal waters over beds of seagrass, sandy flats, and shell and coral rubble. They are found from depths between 9 m (30 feet) and 64 m (210 feet) with adults found in deeper waters than juveniles. The juveniles are born and stay in inshore waters for extended periods of time. They are known make seasonal migrations traveling in groups segregated by size and sex returning to the same locations year after year. They are small stature reaching a maximum of 2.0 m (6 feet 6 inches) in length and 18.9 kg (42 lbs) in weight. The sexes are dimorphic with females grow more slowly, take longer to sexually mature and have longer lifespans than males. As of March 31, 2023, the International Game Fish Association world record for weight stood at 18.86 kg (41 lbs 9 oz) with the fish caught in coastal waters off Little River, South Carolina in July 1992. They feed in large schools on small schooling fish such as anchovies, herrings, menhadens, and sardines, and many other bony fish and octopus and other cephalopods. In turn they are preyed upon by larger sharks including the Dusky Shark, Carcharhinus obscurus. Reproduction is viviparous that involve one or two-year cycles with 8 to 11-month gestation periods and litter sizes of three to six pups that are 38 cm (15 inches) to 50 cm (20 inches) in length that are born in coastal bays and mangrove swamps and are immediately capable of caring for themselves. Juveniles inhabit shallow coastal waters for up to two years to avoid predation and seek food. They have lifespans of up to nineteen years.
The Blacknose Shark are most likely confused with the Atlantic Smalltail Shark, Carcharhinus porosus (second dorsal fin origin over anal fin origin) and the Finetooth Shark, Carcharhinus isodon (very long gill slits).
The Blacknose Shark is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the east coast of the Yucatán Peninsula in the Caribbean.
From a conservation perspective the Blacknose Shark is currently classified as NEAR THREATENED. Although they are widely distributed, they are vulnerable to heavy fishing pressure that have caused significant declines in populations. They are heavily regulated and pursued by recreational anglers being known for its fight on light tackle. The juveniles are prone to high levels of mortality as they are caught and killed as a bycatch of shrimp trawlers, gill netters, and longliners. They are sold commercially dried and salted. They are not considered to be dangerous to humans but are known to display threatened gestures toward divers.