Featured Elasmobranch – Whale Shark
Category : Featured Elasmobranch
RHINCODON TYPUS (SMITH 1828)
FAMILY RHINCODONTIDAE (WHALE SHARKS)
Identification: As the largest fish in the world, the whale shark is hard to mistake. This enormous shark has a slightly flattened head with a terminal mouth. Its flanks have prominent ridges with a prominent pattern of white spots between vertical and horizontal stripes reminiscent of a checkerboard pattern.
Size: The largest reliably measured specimens are a 12.2 m (40 ft) male and an 18 m (59 ft) female, making this species as large as a city bus (40-45 ft).
Distribution: The whale shark is found in tropical and subtropical waters worldwide. Though extremely rare along the California coast, whale sharks have been observed off of Santa Cruz, in Monterey Bay, in the Santa Barbara Channel, and off San Diego. They are very common in the Gulf of California.
Habitat: An oceanic species, the whale shark may be found near the ocean surface close to shore, or far out to sea. They generally inhabit nearshore waters where the temperature is 64 to 86 degrees F. Whale sharks can dive deeper than 240 m. These highly mobile animals may roam for thousands of miles, and often migrate seasonally to specific feeding locations, such as the Bay of La Paz in the Gulf of California.
Biology: A viviparous species, the whale shark is one of the most fecund shark species giving birth to litters of at least 300 young. The embryos develop inside a leathery egg case located within the uterus, and emerge just prior to birth. Size at birth is from 55 to 64 cm (about 2 ft) total length. Growth in newborns is quite rapid at an average of 20-30 cm per year for the first several years. Males mature between 8.5-9.0 m and females at a size in excess of 10 m. The whale shark is a filter-feeder, feeding primarily on plankton, such as copepods, krill, and invertebrate larvae. Its diet also includes jellyfish, squid, small- to medium-sized fish, including anchovies, sardines, mackerel, and even small tunas. Although whale sharks have rows of several hundred small teeth, they feed primarily by swallowing huge volumes of water with the help of suction, and trap their prey on their dense gill rakers by expelling the water through their gills.
General interest: Whale sharks are a huge favorite with divers due to their magnificent size and docile nature. They can currently be seen in captivity at the Osaka Kaiyukan Aquarium in Japan, and the Georgia Aquarium in Atlanta. Whale sharks are considered “vulnerable” by the IUCN (International Union for Conservation of Nature and Natural Resources), although its population size is unknown. Whale sharks are targeted by some artisanal and commericial fisheries around the world. In recent years, several countries have banned the importation and exportation of whale sharks for commercial purposes, including the Philippines (1998), India (2001) and Taiwan (2007).
By Erin Loury
Pacific Shark Research Center
Moss Landing Marine Laboratories
8272 Moss Landing Road
Moss Landing, CA 95039