Reef sharks determined “Functionally Extinct” on 20% of World’s Reefs. In Hawai’i these sharks are protected, but their habitat is being threatened in the Marine National Monuments under the Trump Administration.
July, 26, 2025
Oceanic blacktip sharks, (Carcharhinus limbatus), are a species of requiem shark found in warm, temperate, and tropical waters worldwide, including the Hawaiian Islands.
Referred to as an ‘oceanic blacktip’ to differentiate them from the blacktip reef sharks (C. melanapterus), they are not truly oceanic sharks, but with the reef shjarks, they occupy coastal waters and reefs. They are a robust, fusiform shark, with coloration ranging varying gray to brown above and white below, with a conspicuous white stripe running along the sides. The pectoral fins, second dorsal fin, and the lower lobe of the caudal fin usually have black tips. Fish make up some most of the blacktip shark’s diet. Like other sharks in the requiem family, the blacktip shark is viviparous. Females typically give live birth to four to seven pups every other year. They are known for their agility and fast-swimming nature. This shark is acrobatic especially when hunting schools of fish, with leaps out of the water, sometimes even spinning. These sharks are commonly encountered in coastal areas, in bays, estuaries, and around coral reefs. Most blacktip sharks are found in water less than 30 m deep over reefs and shelves and will often approach the shallows to forage.
The blacktip and other reef sharks are popular sport for recreational anglers in Florida and the Caribbean. Since 1995, the number of blacktip sharks taken by recreational anglers in the United States has approached or surpassed the number taken by commercial fishing according to the IUCN. A 2020 study examined reefs globally and found sharks were absent from 20% of reefs from overfishing, driven largely by dense human populations and poor governance, The study concluded that reef sharks are absent and “functionally extinct” in the waters of eight countries.
Oceanic Blacktip Sharks off Kona Coast, Hawaii. Image David McGuire, Shark Stewards
Protected in Hawaii, these sharks are declining on reefs around the world, including waters along the Eastern Seaboard. The Hawaiian people have a deep connection to the land and sea and the plants and animals they are surrounded by, with a rich oral history interpreting their relationship with nature. Some consider sharks sacred guardians or ‘Aumakua. Agressive interactions with these sharks is uncommon, although they are known to be aggressive around spearing fish, or when threatened by divers. A shark attack on a surfer in Kailua-Kona in 2021 was likely an oceanic blacktip reef shark. This same shark had bee reported by surfers to be acting aggressively in the area the week of the attack. These sharks are known to be territorial on reefs and defend their territory against other sharks.
The blacktip shark is caught in large numbers by commercial fisheries throughout the world, using longlines, nets, bottom trawls, and hook-and-line. This species has been assessed as Near Threatened by the IUCN, on the basis of its low reproductive rate and high value to fishers.
In August, I will be swimming for sharks and maintaining protection in the Pacific Marine National Monuments, including the Papahānaumokuākea Marine National Monument and National Marine Sanctuary. I will also be searching for our local oceanic blacktip shark Bruno.
Fowler, S.L.; Cavanagh, R.D.; Camhi, M.; Burgess, G.H.; Cailliet, G.M.; Fordham, S.V.; Simpfendorfer, C.A. & Musick, J.A. (2005). Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. International Union for Conservation of Nature and Natural Resources. pp. 106–109, 293–295. ISBN 978-2-8317-0700-6.
MacNeil, M.A., Chapman, D.D., Heupel, M. et al. Global status and conservation potential of reef sharks. Nature 583, 801–806 (2020). https://doi.org/10.1038/s41586-020-2519-y