Common name(s)
Brown Smoothhound Shark.
Identification
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. First and second dorsal fin posterior margins, and terminal margin of upper caudal lobe frayed. Lower caudal lobe indistinct. Dorsal coloration brown with bronzy hues. Fins sometimes dusky.
Size
Maximum length 97cm. Size at birth 28-30cm.
Habitat
A temperate water species inhabiting shallow muddy or sandy bays and estuaries. Present in deeper water closer to the equator. Intertidal to 278m.
Distribution
The brown smoothhound shark occurs from Washington State to southern Peru.
Conservation Status
LEAST CONCERN
Although the brown smoothhound is heavily fished in areas of the Gulf of California, there is no evidence to indicate that the population has undergone significant decline. The species is not commercially fished off California, but is taken in low volumes as bycatch and by recreational anglers. This is a fast growing species, with low longevity, early age at first maturity and with relatively high fecundity, giving it a high capacity for recovery from fishing pressure. The life history characteristics of this species, combined with the fact that there have been no suspected, observed, or inferred declines in catches or populations in any region justify an assessment of Least Concern.
Citations and References
Pérez-Jiménez, J., Carlisle, A.B., Chabot, C.L., Vásquez, V.E. & Ebert, D.A. 2016. Mustelus henlei. The IUCN Red List of Threatened Species 2016: e.T161648A80672263. https://dx.doi.org/10.2305/IUCN.UK.2016-2.RLTS.T161648A80672263.en. Downloaded on 22 October 2020.
Reproduction
A viviparous species with yolk-sac placenta. 1-21 pups per litter. Gestation is approximately 10 months. Reproductive cycle is annual.
Diet
Predates heavily on crustaceans but will also eat bony fishes and polychaete worms.
Behavior
The brown smoothhound shark migrates towards the equator during the colder months. Known to swim onto very shallow, enclosed mud flats (e.g. at Elkhorn Slough near San Francisco) to feed.
Reaction to divers
Rarely seen by divers but likely very shy due to its small size.
Diving logistics
Part of the reason that brown smoothhounds are rarely encountered by divers is that they tend to hunt in extremely turbid inshore water. Pier fishermen in San Fransisco Bay consider them abundant so this might be a good spot to dive in order to see one. Unfortunately, visibility in the bay is apparently horrendous so I am not sure if this is a feasible suggestion.
My shots are of released animals that I encountered while accompanying halibut fishermen in Guerrero Negro, Mexico.
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Similar species
Grey Smoothhound Shark This species (and all other smoothhounds present in the eastern Pacific) is distinguished by its dorsal and caudal fins that have un-frayed margins.