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Humboldt State University
Rare shark baffles scientific world
Megamouth shark sightings off the California coast
by Luis Molina
Science Editor
04.16.03
The Megamouth shark is in a class of its own since no other fish in its
family.In the 1970s, a new family of fish was discovered off the coast of
Hawaii. Since the first spotting of the megamouth shark, only about 18 more
sharks have been spotted round the world.
Only one female megamouth shark has been found. Not a lot is know about the
megamouth shark¹s breeding habits, but scientists say it breeds sexually
through internal fertilization.
The babies are miniature replicas of the parents. The captured female had
several whitish ova measuring 5 to10 mm in diameter.
The megamouth shark is a large, slow-swimming, timid shark that mostly roams
the waters of the Pacific Ocean.
According to University of Florida, the megamouth shark is the only known
member of the Megachasmidae fish family. It shares the order Lamniformes
along with the mackerel sharks, such as the great white and basking sharks.
According to the University of Florida, on Oct. 19, 2001, another Megamouth
shark (male, approx. 18 ft. fork length) was caught in a drift gillnet and
released alive in good condition.
A U.S. National Marine Fisheries Service observer was aboard the commercial
swordfish vessel, approximately 42 miles northwest of San Diego. The
observer was able to collect a tissue biopsy and take many color photographs
‹ including one of the upper jaw with white lip and lower jaw with dark
spots on a white chin.
The observer also noted the presence of claspers. Water depth at this
location is 460 fathoms and the sea surface temperature was 65.8 degrees
Farenheit. This is the fourth megamouth shark caught off Southern California
in a drift gillnet targeting swordfish (November 1984, October 1990, October
1999).
The 13th sighting of a megamouth shark was of three sperm whales attacking
it off the coast of Indonesia. There are only seldom sightings of this
species. It lives in the ocean possibly between depths of 150 to 1,000
meters.
The megamouth shark filter-feeds by ingesting tiny organisms ‹ including
zooplankton (like tiny crustaceans) and phytoplankton. It feeds near the
suface at night (it is nocturnal), but each day it descends to a depth of
650 feet (200 meters).
The megamouth shark can grow up the size of 16.5 feet long. It can weigh
about 1,650 pounds.
The megamouth shark is easily recognized by its huge, soft head and large
mouth, which is positioned at the anterior margin of the head. The inside of
the mouth is silvery, and the jaws are covered with many small, hook-like
teeth.
The megamouth shark has two unequal sized dorsal fins, a strongly
heterocercal tail, and lacks any distinctive body markings. Its color varies
from gray to blueish-black above and is pale gray below. The tips of most of
the fins are usually white.
The megamouth shark has been spotted off the coasts of Hawaii, California,
Japan, the Philippines, Senegal, Indonesia and western Australia ‹ in the
Pacific and Atlantic Oceans. It is a deep-ocean creature and comes up to the
surface to feed. They have been spotted in both temperate and tropical
waters of the Pacific.
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