Cause of death of rare oarfish found in La Jolla Cove unclear: scientists

SAN DIEGO (FOX 5/KUSI) -- Scientists have discovered more information about the rare oarfish (Regalecus russellii) that was found dead floating near La Jolla Shores earlier this month.

A necropsy was performed Friday revealing that "the fish was in good condition and it is not clear why the fish died," the University of California, San Diego said in a news release Thursday.

"This male did not have visible signs of milt (sperm) and scientists have previously found that oarfish locally are reproducing in June, but not August and September," the university said.

Scientists determined the deep-sea fish was an adult male measuring 12.24 feet in length, 1.14 feet in depth and weighing 74.3 pounds. Its dorsal fin crest measured 2.17 feet in length, extended from the top of the head.

Oarfish, known as the longest bony fish in the world, can grow to lengths of 30 feet.

On Aug. 10, a team of science kayakers and snorkelers came across the fish in La Jolla Cove and worked together to carry the sea creature from the ocean to the bed of a truck using a paddleboard. The oarfish was then taken to NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla.

The unusual find was the 20th documented oarfish to have washed up in California since 1901.

“Rare encounters like this provide an amazing opportunity to learn more about this species and how it lives,” said Ben Frable, ichthyologist and manager of the Marine Vertebrate Collection at Scripps, who was part of the necropsy team. “We are fortunate to have a large community of researchers and world-class collection that mobilized quickly to examine and preserve this fish.”

In some areas of the world, this species of fish is considered a preview of bad news or a natural disaster, like an earthquake or tsunami. However, experts in a 2019 study found no connection between oarfish or ribbonfish strandings and earthquakes in Japan.

"Scientists also do not know why the fish washed up where it did, though it is generally thought to have to do with injury, illness, and disorientation," UC San Diego said in the release.

Deep-sea fish like lancetfish and footballfish occasionally wash up in the La Jolla Shores, which could be due to the area being next to two underwater canyons that funnel deep water close to shore, according to Frable. Scientists believe that could've been a reason for why disoriented or injured deep-sea fish end up there.

UC San Diego explained that the samples of the oarfish will be used to generate the first high-quality, chromosome-level genome for the longest bony fish in the world; use stable isotopes and genetic barcoding to better understand foraging ecology; look at the filtering anatomy and to inform studies of metabolism and feeding strategies; describe the reproductive status; analyze organs, tissues and body fluids for potential presence of contaminants such as microplastics and DDT; and compare the digestive system with the other species of oarfish, Regalecus glesne. 

The oarfish will become part of the the largest collections of deep-sea fish in the world at Marine Vertebrate Collection at Scripps.

Birch Aquarium at Scripps has also opened a temporary exhibit for the oarfish, which will include artist Dwight Hwang's life-size gyotaku art print of the oarfish in the main galleria.

If anyone finds a unique creature on the beach in Southern California, they are encouraged to alert local lifeguards as well as Scripps Institution of Oceanography at scrippsnews@ucsd.edu or 858-534-3624.

FOX 5/KUSI's Amber Coakley contributed to this story.