Oarfish offer chance to study elusive animal
November 03, 2013 2:40 AM
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It was a big day for marine biologists: On Oct. 13, the body of an 18-foot oarfish was dragged from the water onto Santa Catalina Island off the California coast, presenting a rare opportunity for local scientists to study one of the world’s most elusive and awe-inspiring big fish.

Five days later, it was a big day again: Another oarfish washed up 50 miles away, this one 14 feet with 6-foot-long ovaries full of eggs.

Pairs of oarfish have appeared within days of each other before, deepening the mystique that surrounds the animal. But the twin discoveries nevertheless sent a wave of excitement through a scientific community more used to reading about oarfish than handling them in the lab.

“These are unpredictable fish,” said Dr. Milton Love, a research biologist at the Marine Science Institute of the University of California, Santa Barbara. “And it’s hard to study unpredictable fish.”

Oarfish, which are long and eel-like in appearance, can grow to stupendous lengths — though ancient rumors of 55-foot specimens are probably exaggerated — and have inspired tales of sea monsters since ancient times.

Scientists know very little about them because they are “virtually never caught in nets or by hooks, and they’ve only been observed under water a handful of times,” Love said. “So you’re kind of left with these not random but rare events, and that’s the only way you can study them.”

It is known that oarfish are notoriously bad swimmers; their long bodies remain still while their undulating fins handle most of the propulsion, yet they have apparently learned to avoid nets, Love said.

Precisely what will be learned from the two newfound fish, which were dissected and divvied up among a handful of research institutions, remains to be seen.

“You can only learn so much from a dead fish,” Love said. But by last week, a coterie of researchers, including a comparative ophthalmologist and a gill expert, were lining up to study them.

Early observations revealed that the second fish, found in Oceanside, was apparently ready to spawn.

“There were probably hundreds of thousands of eggs in those ovaries,” said Dr. H.J. Walker, the marine biologist at the Scripps Institution of Oceanography who extracted the eggs. Its stomach was nearly empty, supporting the theory that a strong current, possibly the northeast-flowing Kuroshio, had carried it and the other oarfish, a male, away from their preferred environment and food sources. A variety of parasites, including large larval tapeworms and a spiny-headed worm, were found in the intestines of the male, potentially giving a clue about where these particular oarfish lived and fed. Their species, Regalecus russelii, is most populous in the Western Pacific.

Oarfish fans noted with excitement that the male was missing some of the posterior part of its body, colloquially known as the tail. Dr. Tyson Roberts, an ichthyologist with the Smithsonian Tropical Research Institute who is widely regarded as the world’s leading oarfish expert, has long hypothesized that oarfish can jettison sections of their bodies below the abdomen, much the way lizards can shed their tails.

As the world’s largest bony fish, oarfish have no known natural predator, so unlike with lizards, any shedding of the body is probably not done in self-defense, Roberts said. Such behavior is more likely meant to make swimming more efficient, among other reasons.

“There may also be energetic benefits in shedding the posterior part of the body if it does not have much survival value, as apparently is the case in oarfishes,” he added.

Even oarfish experts disagree on some basic facts. Most refer to them as deep-sea creatures, contending that they live 500 to 1,000 feet below the surface. Roberts says that is not so.

“Mostly they spend their time quite near the surface, suspended vertically with their heads up, just passively floating,” said Roberts who championed the idea that there was more than one species of oarfish. He also believes that they have the capacity to change gender.

“It may be that all individuals pass through a stage in which they are males and then pass through a stage in which they’re females,” he said.

Just how deep the oarfish resides may become clearer in the coming months as researchers study the eyes of the new specimens, possibly learning whether they are designed to see in the low light of the deep ocean.

“There’s not much information on the oarfish eye, which is unusually large,” Walker said.

At California State University, Fullerton, Misty Paig-Tran, a biomechanist, will use CT scans to make a three-dimensional model of the female specimen, most of which she now possesses (the head will soon be delivered to Walker). Her preliminary X-rays gave researchers a closer look at the structures that support the dorsal fin, which may help explain the animal’s unusual way of swimming.

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