Pacific Sharpnose Shark.
Slender body. Snout very long and pointed. Long, deep labial furrows around mouth. Conspicuous row of hyomandibular pores extending backwards from the mouth. First dorsal fin origin over pectoral fin free rear tip. Second dorsal fin origin level with middle of anal fin base. Dorsal coloration grey-brown or bronze. Posterior margins of pectoral fins pale edged. Posterior margin of upper caudal lobe often dusky or black.
Maximum length 116cm (Castillo, Geniz 1990). Size at birth 33-34cm.
Found over soft mud and sand in warm temperate and tropical waters. Intertidal to 27m but suspected of moving into deeper water in the Gulf of California during the summer.
The Pacific sharpnose shark is limited to the coastal Eastern Pacific from Southern California to Peru including the Sea of Cortez.
The Pacific sharpnose shark is captured as bycatch in demersal shrimp and hake trawl fisheries and in teleost traps, and is targeted by artisanal gillnets and longlines throughout much of its range. These fisheries are generally intense in the Eastern Central and Southeast Pacific. There is evidence of a population reduction including an increasing rarity of landings and anecdotal evidence from fishers. Gillnet pressure in the Gulf of California, Mexico, is high and has led to declines in pelagic sharks, and smaller coastal sharks are increasingly targeted without management (or inadequate enforcement of regulations). Shrimp trawling is substantial off southwest Baja California Sur and also off Mazatlan, where declines in catches in other species, overcapacity, and poor governance have been highlighted. Throughout its Central and South American range, the species is subjected to intense fishing pressure. Recent landings surveys in Costa Rica have recorded relatively few individuals, and anecdotal evidence from fishers indicates that they were previously much more common. In Colombia, this species is recorded in artisanal fisheries at lower frequency than the 1990s. Mangrove habitats, which often serve as nursery areas for coastal sharks such as this, have been degraded with the development of shrimp aquaculture in many areas of the Eastern Central Pacific. Although this species has a relativity high biological productivity, a lack of management and enforcement throughout most of its range precludes sustainability. This shark may have some refuge from fishing in southern California and the relatively remote Pacific coast of Baja California. Overall, due to the level of intense and largely unmanaged fisheries operating in its range, its increasing rarity in some areas, and the degradation of coastal mangrove habitats, balanced with some areas of refuge, it is suspected that the Pacific Sharpnose Shark has undergone a population reduction of 30–49% over the past three generations (15 years), and it is assessed as Vulnerable A2cd.
Citations and References
Pollom, R., Avalos, C., Bizzarro, J., Burgos-Vázquez, M.I., Cevallos, A., Espinoza, M., González, A., Mejía-Falla, P.A., Morales-Saldaña, J.M., Navia, A.F., Pérez Jiménez, J.C., Sosa-Nishizaki, O. & Velez-Zuazo, X. 2020. Rhizoprionodon longurio. The IUCN Red List of Threatened Species 2020: e.T161662A124524022. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T161662A124524022.en. Downloaded on 19 February 2021.
A viviparous species with yolk-sac placenta. 1-12 pups per litter. Gestation approx. 10-12 months. Annual reproductive cycle.
Diet consists of small bony fishes and crustaceans.
Poorly known. Likely stays close to the bottom on muddy and sandy substrates where it feeds. Probably migrates into deeper water during the summer.
Reaction to divers
Unknown, but likely very shy due to its small size.
Rarely if ever encountered by divers. The images on this page are of released animals, that I encountered while accompanying artisanal shark fishermen in the Sea of Cortez. Although they thought it was an odd request, the fishermen let me buy the sharks for a few dollars and liberate them.
On the day that I went to sea with the fishermen, we took a small panga out of Mulege, Baja. They baited 400 hooks on 2km of longlines. For this effort, they retrieved 7 small sharpnose sharks, which they told me barely paid for their bait. In contrast, the oldest fisherman on the panga told me that 30 years prior, he had gone to sea with a much shorter longline baited with 100 hooks. On that day, they caught so many sharks that the panga was ‘filled to the gunnels’ and in danger of sinking as it returned to port.
Although this species is still considered relatively common, it is clear to me that fishing effort should be reduced or banned altogether until its numbers increase significantly.