For researchers, the teeniest fish is a jumbo find

Small fry: Measuring in at a third of an inch or less, the stout infantfish is the smallest known animal with a backbone.

Medicine & Science

August 02, 2004|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

Researchers in California say they have discovered a new fish that's unlikely to ever reach a dinner plate - it takes 500,000 to make a pound.

Measuring only a third of an inch or less, the stout infantfish found off Australia's Great Barrier Reef is not only the world's smallest fish, but the smallest creature ever discovered with a backbone.

Researchers at the Scripps Institution of Oceanography and the National Marine Fisheries Service in San Diego published their discovery in last month's issue of Records of the Australian Museum, an Australian scientific journal.

Just six stout infantfish have ever been caught. The only female fish measures a third of an inch. The largest of the five male specimens is a mere quarter-inch, but that's not unusual: Male fish are often smaller than their egg-bearing counterparts.

But minuscule size isn't the animal's only unusual trait. The stout infant fish, one of three species of the breed, is believed to have a life span of only two months. It's transparent except for its eyes. It also lacks teeth and scales and never advances beyond its larval state.

The first stout infantfish was caught in 1979 by Jeff Leis, a researcher at the Australian Museum, using a plankton net to search for tiny fish in the Lizard Island area of the Great Barrier Reef. The five other specimens were collected in the 1980s.

Researchers at Scripps and the fisheries service first saw the fish about four years ago when Leis sent one to his U.S. colleagues for examination.

"I said, `Wow! This is a new species, without a doubt,' " recalled H.J. Walker Jr., a senior Scripps scientist and a co-author of the report.

The identification process began about two years ago. Leis, busy with other projects, gave approval to Walker and National Marine Fisheries scientist William Watson to begin looking into whether his catch was a new species.

"We were all involved in other projects, so it took some time to get to it, which isn't that unusual," Walker said.

The discovery supplants the dwarf goby as the world's smallest fish. The goby, a freshwater creature from the Philippines, had reigned since its discovery in 1981. The world's largest fish is the whale shark, which grows to more than 50 feet, can weigh several tons and is found in the Gulf of Mexico. (Whales are not fish. They're mammals.)

Among ichthyologists, the discovery is about as exciting as it gets.

"It's always great to find something that lies on one extreme end of a spectrum," said George Burgess, a fish expert at the Florida Museum of Natural History credited with discovering the world's smallest shark - the eight-inch lantern shark found off Venezuela - in 1985.

Burgess said the discovery underscores the need to continue searching the world's oceans and forests for exotic animals before they disappear. "It signals how important it is to be out there looking and describing the biodiversity we have on this earth," Burgess said. "These things are disappearing before we even know about them."

Experts say that while there are about 25,000 known species of fish, many species remain undiscovered - and there may be even smaller fish to be hooked.

While the freshwaters of the United States have been well explored, a new species, the shoal bass, was discovered as recently as 1999 off the Florida panhandle.

"What we know about fish is largely based on our ability to catch them," Burgess said. "I wouldn't be surprised to see us get up to 40,000 species before we're done, and who knows when we'll ever be done."

Walker conceded a smaller fish may one day turn up.

"I think it's possible," he said.

Whether the stout infantfish is actually a separate species from the two other types of infantfish previously documented will be evaluated by fish experts around the world, as the paper circulates among scientists.

What distinguishes one species of fish from another is the presence of distinctive characteristics - such as color, size and the number and positioning of scales, fins or a spine.

Walker said the stout infantfish's distinguishing traits include its lack of teeth and the number and position of its dorsal and anal fins. He said he's confident the finding will survive scrutiny from other scientists.

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