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Odd Fish - National Aquarium Seahorse Breeding Program - 2002-11-24


Seahorses are fish that don't look-like, swim-like, or reproduce-like fish. With a head resembling that of a tiny horse, seahorses and their biological cousins, sea dragons, live in shallow tropical seas and temperate waters. One of the world's leading seahorse research laboratories, dedicated to breeding the fish, is located in the seemingly-unlikely setting of a busy inner harbor in Baltimore, Maryland. The city's National Aquarium and its nearby lab have already successfully bred 12 species of seahorses and have a new exhibit of the fish on display.

With soothing new-age music in the background, dozens of seahorses swim peacefully in a series of display tanks in a large area of the National Aquarium. Jim Anderson, seahorse program manager for the aquarium, says some first-time visitors believe seahorses are actually imaginary creatures. "There's a fair amount of mythology associated with seahorses," he says. "They pulled 'Neptune's chariots' through the oceans. They were in the 'Little Mermaid' [story]. For the most part, that's people's only real-life experience with them. So when they come to the aquarium here and see that they are indeed real, it's often a surprise. They are not real common among the pet trades, so it's not like other fish that people might see readily at a pet store. It's only at an exhibit like this that they'll see them in person."

Mr. Anderson says that perhaps one reason that some people don't believe seahorses really exist is their unusual traits. "Seahorses are indeed fish. As with all fish, they share the characteristics of having fins and gills," he says. "But that's the extent of the generalizations we can make. There are separate sexes, male and female. They reproduce by producing eggs. In seahorses, unlike in any other group of animals, it's the male that becomes pregnant and incubates the eggs. So there's a real difference between seahorses and other familiar fishes."

Other unusual characteristics of a seahorse are its upright stance, with its prehensile tail - which allows it to hold on to coral and other sea objects. Their tiny size, usually less than 15 centimeters, gives them a "jewel-like" appearance. And seahorses don't have the scales of typical fish; instead they have a dark, exo-skeleton of bony plates for protection and camouflage.

A biological cousin of seahorses, the sea dragon, has similar characteristics, says Jim Anderson. "Sea dragons are in the same family as seahorses. Sea dragons have more of a horizontal orientation, so it's like a seahorse that's lying down on its front side. It still has that wonderful tube snout as all members of its family have that they use to slurp up their food," he says. "Sea dragons are larger than seahorses and are found only in Australia whereas seahorses are found worldwide in all shallow, temperate, tropical seas."

The rarity of some sea dragons has led to severe restrictions in its breeding methods, as Mr. Anderson explains. "The leafy sea dragon is only found in Australia and is well-protected by the Australian government as an endangered species," he says. "As it stands now, there's only one individual in Australia who has a permit from the Australian government to collect a single, pregnant male each year. He brings a male into the lab, where he gives birth. [Then the collector] has to put 'dad' back into the ocean, and [the collector] will raise the young. He's the sole source worldwide of these [sea dragons]. So any distributed each year are siblings."

From his office, the National Aquarium's Jim Anderson takes a reporter to their breeding labs in the nearby Center for Marine Biology building. In a room full of large water tanks, hooked up with tubes and gadgets, Mr. Anderson describes the elaborate efforts to provide the right food for their seahorses. "We've got here adult artemia or brine shrimp. The adults are purchased from a commercial culture and held here," he says. "We also hatch out the juvenile version of the artemia and grow it out here, enrich it, and then feed it to the seahorses and [related] pipefish."

Because of their tiny size, seahorses present a special challenge to feed, especially for younger ones: "Because of the size of the juvenile seahorses - as juveniles, they eat live food. So the challenge is to get live food that's small enough that they can slurp it up.

"We've got a little bit of breeding going on now. We don't always have 'kids in the nursery.' There are a couple of things I can show you. [You might want to step on the stool if you want to.] If you look down at the top, those guys are dwarf seahorses from the Florida coast and Caribbean area. This is the second generation for us. The adults were wild-collected and brought to the lab here and put through a standard quarantine. We actually had one of the males come in pregnant, and it gave birth right away. We were able to raise the young, and his offspring have given birth to another batch. So this is the second generation of this particular group."

Just as it's a challenge to feed seahorses, it's also a challenge to eliminate waste from breeding tanks and provide pure water, as Jim Anderson explains. "We do have the typical water bubbling from an aerator," he says. "It's a plastic medium in there in which the bacteria will break-down fish waste and will colonize and grow on the outside of [the plastic]. They need good aeration, so we have the air and bubbling to keep them rotating like that. And the waste serves as the food that the bacteria feed on."

For the National Aquarium exhibit, seahorses from around the world were collected. But Mr. Anderson says the aquarium's staff biologists were able to locate some seahorses in a relatively nearby site. "Some of our [collection] we collect from the wild ourselves particularly those found in the Chesapeake Bay, in southern Maryland or Virginia," he says. "One that occurs locally is the northern pipefish. What we did was collect a few pregnant males, brought them into the lab where they gave birth- and we were able to grow [the babies] up here. We can't say they were 'captive-born,' but they were 'captive-reared.' This way we only need to collect a few animals and yet end up with 50 to 75 for our exhibit."

Jim Anderson, seahorse program manager at the National Aquarium in Baltimore, Maryland, who is leading an effort to preserve the unusual fish species.

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