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Soupfin sharks appear to return to the same spot in La Jolla once every three years, UC San Diego discovers

UC San Diego has found evidence that some soupfin sharks visit La Jolla once every three years.
(Courtesy)

UC San Diego has discovered that some female soupfin sharks return to a specific area of La Jolla once every three years for reasons that are not entirely clear.

The finding is based on the movements of 34 pregnant soupfins that were tagged with acoustic transmitters so they could be tracked as they migrated between La Jolla and points north, mostly the northern Channel Islands and San Francisco Bay.

The sharks that returned in three-year cycles spent part of the summer in the warm shallows just south of La Jolla’s Marine Room. Their arrival coincided with their three-year reproductive cycle.

The creatures were probably using the warm water to incubate their embryos, according to Andy Nosal, a researcher at UCSD’s Scripps Institution of Oceanography in La Jolla.

“These are the only animals that we know of that return to the same spot once every three years,” said Nosal, whose findings were published in the Journal of Applied Ecology.

This behavior is similar to that seen in other sharks. Nosal previously found that female leopard sharks, guitarfish and bat rays make annual trips to La Jolla consistent with their reproductive cycles.

Soupfin sharks are sleek animals that can grow up to 6 feet 5 inches long and weigh about 100 pounds. They do not pose a threat to humans. They were heavily fished along the California coast in the 1930s and ‘40s, partly because their liver oil contains a lot of vitamin A. The demand for the sharks declined after scientists synthesized the vitamin, according to the Monterey Bay Aquarium.

The species is called soupfin because its fins often have been harvested to make Chinese soups. ◆