The annual return of Leopard sharks to La Jolla Cove has become a famous local tourist attraction, but the La Jolla Shores and La Jolla Cove are also a nursery site for many marine animals including sharks. The warm shallow cove is part of California’s Marine Protected Area network and some of the cove is a no-take marine reserve protecting habitat and sharks while in the reserve. Many species of sharks and rays that frequent the cove are pregnant, using the warm waters to gestate and forage.
A new acoustic shark tagging study by Dr. Andrew Nosal, a shark scientist at Scripps Institution of Oceanography, reported that every three years the same soupfin sharks (Galeorhinus galeus), return to La Jolla shores. In a 7-year long study, Dr. Nosal and the Scripps team have found that the same female soupfin sharks, some carrying 40 to 50 pups, return to the cove after a three year absence.
Also called the Tope shark or School shark, Soupfins are often found in schools of more than 50 individuals and may travel hundreds of miles to breed. Females incubate eggs within their body, giving birth to up to 52 pups after a yearlong gestation period. Another interesting finding is that some of these pups have different fathers with one female shark becoming impregnated by several male partners. This trait diversifies their genetic make up and increases survival of the young, and the species.
A sveldt shark in the Houndshark family Triakidae, these sharks grow up to 6 feet 5 inches and 100 pounds. Soupfins are highly prized for their meat and fins, which are used in a number of Asian dishes, including traditional sharkfin soup.
“Species habits including range and movement patterns can help protect this critically endangered species.Dr. Andy Nosal
In the 1940s and 50s the soupfin shark population was nearly eradicated for their large livers which are rich with vitamin A. A large commercial fishery existed off the San Francisco Bay, where the newly immigrated Chinese favored them for their fins, giving them their name. Since the synthesis of vitamin A, the soupfin sharks and sevengill sharks are no longer targeted commercially in California, but they are caught by sports fishermen along the West Coast and in the nursery area of the San Francisco Bay.
In the Northeast Pacific, the Soupfin shark ranges from British Columbia to northern California. In the northern part of the range most soupfins are males. In southern California, females predominate. Along California’s central coast and in the San Francisco Bay, which is an important breeding and pupping area, there are roughly equal numbers of males and females. Their diet consists of fish, crab, shrimp, lobster, cephalopods, worms and echinoderms. This species is widely distributed in temperate oceans and their range includes South America, Australia, New Zealand, South Africa, and Europe.
(San Diego Channel 8 news on the findings of Dr. Andy Nosal)
In La Jolla, the soupfin sharks usually arrive in April and inhabit the coast including the Channel Islands through fall. The females then move up north to the Central Coast and Bay Area where they birth their babies and reproduce, renewing the cycle. Males typically swim further north near Washington and Canada where they are fished commercially. Females also extend south along the coast of Baja California, Mexico where they are often caught in gillnets.
Listed by the International Union for the Conservation of Nature (IUCN) as Critically Endangered globally, these sharks are declining. Understanding habitat use, behavior, migration and biology can help us better protect the west coast population. Marine Protected Areas help protect them while in the no take areas, but these wide ranging species are killed as bycatch in the California drift gillnet fishery, and are targeted by sports fishermen. Recording catch and kill, catch and release and divers observation of live sharks is part of Shark Steward’s Shark Watch program to increase our knowledge and provide better management of California sharks.