Dusky Smoothhound Shark, Smooth Dogfish.
Body slender. Snout fairly long and pointed. Upper labial furrows noticeably longer than lower. Small, visible spiracle behind eye. First dorsal fin origin over pectoral fin free rear tip. Second dorsal fin much larger than anal fin. Lower caudal lobe distinct, with a rounded tip. Dorsal coloration olive-grey or grey-brown. Fins usually dusky with white tips and posterior margins.
Maximum length 152cm. Size at birth 28-39cm.
A temperate / sub-tropical species usually inhabiting shallow muddy or sandy bays and estuaries. Island subspecies in some parts of the Caribbean are found in much deeper water; down to 808m.
The dusky smoothhound shark has a fragmented range along the western Atlantic. In the north, it occurs from Canada where it is seen very rarely, down to Florida, as well as throughout the Gulf of Mexico and the Caribbean Sea, southward to Venezuela. In the southern hemisphere it occurs from southern Brazil to northern Argentina.
An abundant species seasonally in many areas of the northwest Atlantic, in recent years they have become commercially important in this region. Recent rapid increases in directed gillnet fishing has caused a decline in some stocks of large females. There is currently no management plan or protection for this species.
Historically this species has not been utilized in fisheries, except for collection to use in classroom exercises (Bigelow and Schroeder 1948). Compagno reports that this species is fished off Cuba, Venezuela, Brazil and possibly other locations in the Caribbean, using longline gear and bottom-trawls and is utilised as a food resource (Compagno 1984b). Recently a gillnet fishery for dusky smoothhounds has started on the eastern shore of Virginia and North Carolina. Total landings of Dusky Smoothhounds in Virginia waters remained fairly low (less than 25,000 lbs or 11 t) until 1993 when landings exceeded 220,000 pounds (100 t). Total landings remained around this level for two more years but decreased to around 140,000 pounds (63.5 t) in 1996 (Virginia Marine Resources Commission unpubl.). In North Carolina Dusky Smoothhound landings have only been reported separately from Spiny Dogfish (Squalus acanthias) landings since 1995. In 1995 total landings reached 2,182,577 lb (990 t) but dropped in 1996 to 463,047 pounds (210 t) (North Carolina Division of Marine Fisheries unpubl.).
Citations and References
Conrath, C. 2009. Mustelus canis. The IUCN Red List of Threatened Species 2009: e.T39359A10215463. https://dx.doi.org/10.2305/IUCN.UK.2005.RLTS.T39359A10215463.en. Downloaded on 25 October 2020.
A viviparous species with yolk-sac placenta. 10-20 pups per litter. Gestation is approximately 10 months. Reproductive cycle is annual.
Predates heavily on crustaceans (shrimps, crabs, and lobsters) but will also eat small bony fishes if readily available.
In North America, smooth dogfish spend the summers in the north; from Chesapeake to New England. Once temperatures begin to drop in the fall, they move further south, wintering off South Carolina to Central California, returning in mid May to their summer hunting and breeding grounds.
Reaction to divers
Rarely seen by divers but likely very shy due to its small size.
I am not aware of any specific spots where dusky smoothhounds can be reliably encountered by divers or snorkelers but I suspect that they are probably fairly easy to attract on snorkel by baiting in sheltered, shallow bays between Washington D.C. and southern New England, wherever calm clear water can be found.
Gulf Smoothhound Shark Difficult to distinguish in the field. Differs in having a slightly more pointed snout and slightly more narrowly rounded lower caudal lobe. Tooth and denticle shape are definitive traits if closer examination is possible.
Narrowfin Smoothhound Shark Distinguished by its more distinct ‘hooked’ lower caudal lobe with a pointed tip.