First silky shark sightings by Saba Conservation Foundation

Whilst nurse sharks and Caribbean reef sharks are regularly spotted on the Saba Bank, it’s not every day that you see silky sharks. During a routine visit to the Saba Bank, a research team from the Saba Conservation Foundation (SCF), Saba Bank Management Unit, made history a few weeks ago when Oceaware’s Guido Leurs spotted around 10 juvenile silky sharks (Carcharhinus falciformis). This was the first time that silky sharks had been reported from the Saba Bank.

Some of the defining characteristics of the silky shark include a small, rounded first dorsal fin that originates behind the end of the pectoral fins, a much smaller second dorsal fin with a free tip that is twice as long as the height of the fin together with long, slender pectoral fins that typically have dusky tips.

These slender oceanic sharks get their name from the smooth, silky texture of their skin which is caused by dermal denticles that are unusually densely packed. Silky sharks inhabit both deep oceans and shallow coastal waters and are highly migratory. The silky shark population in the Western Atlantic follows the Gulf Stream as well as the movements of tuna and swordfish, their main food source.  Their appetite for these schooling fish makes them extremely vulnerable to by-catch, and many silky sharks are caught and killed in pelagic longline fisheries or are trapped in purse seines targeting tuna and swordfish.

There are also targeted silky shark fisheries in operation in the Caribbean and Gulf of Mexico, where they are caught by longlines. Silky sharks are ranked amongst the three most important sharks in the global shark fin trade - with up to 1.5 million fins being traded annually from this species. Population data for this species shows a worrying downwards trend since the early 1990s, especially in the northwest and western central Atlantic. The IUCN Red List status of the silky shark was adjusted in 2017 from “Near Threatened” to “Vulnerable” due to an estimated 47-54% decline of the global population over three generations. Silky sharks are especially vulnerable to exploitation because of their life history characteristics: a long gestation period, a slow growth rate, small litters and a long reproductive period. Safeguarding the future of this highly migratory species will require a cooperative approach between all countries through which it migrates, and an increase in safe havens like the Yarari Sanctuary and the Saba Bank.

For more information: http://guidoleurs.org/silky-sharks-new-shark-species-saba-bank/

This news-tem was published by DCNA in BioNews12-2018.