Fish Identification Photos: Megamouth Shark, Megachasma pelagios: The Megamouth Shark is an exceedingly rare fish species with the first collection made from a Navy ship in Hawaiian waters on November 15, 1979. The second collection was not made until eight years later, and to date only 38 have been documented. The Megamouth Shark is the sole member of the Megachasmidae Family and the most primitive living species in a group which includes the Basking, Mako, Salmon, Sand Tiger, Thresher and White Sharks. This species has a wide range, found in the tropical waters of the Atlantic, Indian, and Pacific Oceans. Four of the 38 Megamouth collections were made off the coast of Southern California and two from waters off Baja California.

The dorsal surface of the Megamouth Shark’s body and most of the fins are blackish brown. The ventral surface, tips of the pectoral and pelvic fins, and margins of the anal, caudal and dorsal fins are white. The Megamouth Shark has a stout body that tapers posteriorly. The head is large, bulbous, wide, and long with a very short and broadly rounded snout that has a large terminal mouth, the corner of which extends behind the eyes. The inside of the mouth is silvery and the jaws are covered with many very small, hook-like teeth. The gill slits are moderately long, but do not reach the dorsal surface of the head.

The first dorsal fin originates closer to the pectoral fin base than to the pelvic fin base. The dorsal fins are relatively low and the second dorsal fin is less than half the size of the first dorsal fin. The caudal fin is strongly heterocercal with a very long upper lobe and a much smaller lower lobe. The caudal fin base is without keels or ridges.

The reproduction process of the Megamouth Shark is not well understood, but is believed to include a large number of whitish-yellow eggs. Details about predators of this species are limited to attacks by Sperm Whales, Physeter macrocephalus (one visual citation), by Cookiecutter Sharks, Isistius brasiliensis (evidenced by residual bite marks), and parasites (found on the surface of and inside collected species).

The Megamouth Shark is a filter feeder that consumes planktonic shrimp, copepods, and pelagic jellyfish. It is believed to be similar to the basking and whale sharks but is less active, a poorer swimmer, with a flabby body and soft fins.

The Megamouth Shark is believed to be a vertical migrator, spending daytime hours in waters as deep as 3,000 feet and ascending to midwater depths of 50 feet at night. The largest collection made to date was 17 feet in length and 1,800 pounds.

Due to a lack of information concerning distribution and population, this species is considered “Data Deficient” by the World Conservation Union (IUCN).

Megamouth Shark, Megachasma pelagios: Female. Caught off the coast of Bahía Tortuga, Baja California Sur, Mexico, by commercial fishermen of the F/V “Corina del Mar” under Capt. Edén Magaña, in a gill net, on November 16, 2006. Size 214.9 centimeters (7.05 feet) and 27 kilograms (60 pounds). Identification courtesy of Joe Leonardo Castillo-Géniz, National Fisheries Institute of Mexico, Ensenada. Photos courtesy of Dan Cartamil, Scripps Institute of Oceanography, La Jolla, Calif. Description courtesy of John Snow.