March Elasmobranch of the Month: Silvertip Shark
Author: Linda Weiss
Silvertip sharks are a relatively large species, averaging in length between 1.8-2.4 m (6-8 ft). The maximum recorded Silvertip measured 2.9 m (9.8 ft) long and weighed 162.2 kg (357.6 lbs). As their name suggests, they can be identified by the silver tips and borders on all of their fins. Their body shape is slender with an interdorsal ridge and a long and broadly rounded snout. Body coloration is bluish-gray, often with a bronze hue on the top and sides and white underneath. The first dorsal fin and the pectoral fins have slightly rounded tips. The caudal fin is forked with the upper lobe roughly twice as long as the lower lobe. Both the upper and lower jaws of this shark species contain 12 -14 serrated teeth each. The teeth in the upper jaw are triangular in shape, and while also triangular, the teeth in the lower jaw are narrower and more pointed.
Habitat and Distribution
This shark species can be found in the tropical waters of the Western and Eastern Pacific Ocean, the Western Indian Ocean and the Red Sea. Juveniles are typically located in more shallow waters, away from predators. Adults can be found at depths of 800 m (2,625 ft) and reside both inshore and offshore over continental and island shelves, as well coral reefs.
The Silvertip’s diet includes fish such as wrasses, tuna, wahoo and smaller sharks. It’s also known to prey on eagle rays, squid and octopuses.
This shark species mates once a year during the summer. Gestation is 12 months. Reproduction occurs viviparously, where the young develop inside the female, receiving nourishment through a placental sac before being birthed alive. Litter sizes range typically between 5-6 pups, that are 0.5-0.8 m (1.6-2.6 ft) long. Litter sizes up to 11 are possible. Both males and females reach sexual maturity when they grow to about 1.6 m (5.2 ft) in length.
The IUCN Red List of Threatened Species currently lists the Silvertip shark as Vulnerable, with a decreasing population trend.
Juvenile Silvertip sharks’ natural predators are larger fish, including sharks. Humans pose the biggest threat to this species, taking them from the ocean to use their fins in shark fin soup, their muscle for meat, teeth for souvenirs, their liver oil for cosmetics and their cartilage for supplements.
Shark Research Institute
The IUCN Red List of Threatened Species
Espinoza, M., González-Medina, E., Dulvy, N.K. & Pillans, R.D. 2016. Carcharhinus albimarginatus. The IUCN Red List of Threatened Species 2016: e.T161526A68611084. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T161526A68611084.en. Downloaded on 15 March 2021.