Beyond the Fathoms of Our Imaginations

More than a half-mile down in the dark depths of the ocean, researchers are uncovering a bizarre world of fish life

02-01-1992 // Mark Wexler

They look like science fiction monsters, and in many respects, they act the part. Yet the more researchers learn about the strange species of fish that live in deep ocean waters throughout the world, the more they appreciate the abilities of these creatures to survive in such a dark, inhospitable environment. "We've discovered dozens of species of miniature 'monsters' that have adapted to living at depths where people once thought little life existed," says Richard Rosenblatt, a marine biologist at Scripps Institution of Oceanography in California.

For the past three decades, Rosenblatt has presided over one of the world's largest collections of deepwater fish--part of a Scripps collection that now includes more than two million specimens of Some 4,000 species, primarily from the Pacific and Indian oceans. Scripps scientists began collecting deep-water specimens at the end of World War II in an effort to learn more about life in the most unexplored regions of the planet.

"Much of the ocean life we are familiar with lives in the top few hundred feet of water where sunlight penetrates," says Rosenblatt. "But that productive top layer represents less than 5 percent of the ocean's total volume. Can you imagine how much territory remains unexplored?"

Using robot submersibles and nets trolled far beneath the surface by research ships, Rosenblatt and his associates have discovered species living at depths of between a half-mile and three miles down. (Scuba divers rarely go deeper than 300 feet.) "These creatures cannot survive at sea level because they are adapted to living in such extreme water pressure and temperatures," says Rosenblatt. "Rut even in a preserved state, they are invaluable to science. Unlike many books, these specimens will never go out of date. There is no limit to what we can learn from them."

Fish specimens, the biologist points out, were crucial to research in the 1970s, when Americans became concerned about mercury contamination in certain fish. Ichthyologists at the Smithsonian Institution in Washington, D.C., tested specimens of the same species that had been collected in the 1800s and found that mercury levels had not changed significantly over the decades, thus calming public fears.

The specimens displayed on these pages were photographed at Scripps by California oceanographer Norbert Wu. None is more than a foot in length, and each represents an example of remarkable evolutionary adaptation.

In the pitch darkness of water 3,000 or more feet deep, far fewer creatures live than at shallower depths. That means finding a meal--or a mate--can be extremely difficult. Deep-water fish must be opportunists, capable of eating anything that comes their way. Equipped with enormous mouths and teeth, certain anglerfish, for example, have been recorded taking prey two to three times their own size. Another creature, the deep-sea swallower, has a huge head and hinged mouth that opens like a garbage truck to engulf a meal.

Many of these fish have evolved elaborate light sources to attract prey. The anglerfish has a long "fishing rod'' attached to its basal hone, with a luminous bulbous light lure at the tip that can be wiggled about. The viperfish, on the other hand, has light organs directly inside its mouth to lure prey into a waiting stomach.

The most specialized light source may belong to a small predatory fish called Pachystomias, which emits a red beam from an organ directly under its eye. Because most fish cannot see red, the creature can use its beam like a sniperscope, sighting and then moving in on its target without detection.

How do deep-water fish manage to find mates in such vast territories? "It's still a mystery," says Rosenblatt. "But we do know that in some species males have well-developed eves to detect flashing bioluminescense, which can lead them to flashing hires of their female partners."

By studying specimens over several years, Scripps researchers have pieced together an unusual behavior among anglerfish, designed to ensure that any mating encounter will be fruitful. When he locates a female of his species, the male--only about one-twentieth the size of his mate--attaches himself to her with his mouth and rides along. Eventually, his body fuses to hers and blood vessels form between the couple, through which nutrition passes to the male. In time, the male degenerates into not much more than a portable sperm supply.

"Much of what we know about these creatures is speculative," says Rosenblatt. "Because they live so far down, we just can't observe them properly. And, of course, we're continually discovering more species." Who knows, he adds with a twinkle in his eye, "what unseen monsters are still lurking in the dark depths of the sea?"

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