Monday, June 25, 2012

UM marine school experiments with raising dolphin fish

From Miami Herald:  UM marine school experiments with raising dolphin fish

They grow fast, have lots of offspring, and die young. Most people like to eat them and there’s more commercial effort to harvest them than ever before. The aquaculture program at University of Miami’s Rosenstiel School is growing them in tanks and aims to teach other fish farmers how to do it.

Dolphin fish, also known as mahi mahi, is the latest experimental research species at UM’s aquaculture lab on Virginia Key. The colorful pelagics join cobia, blackfin tuna, Florida pompano and goggle eyes swimming around in large fiberglass tanks.

“They are iconic yet elusive,” professor Dan Benetti, director of the university’s aquaculture program, said of dolphin. “There’s got to be somebody interested in raising these fish commercially.”

Growing dolphin in captivity is nothing new; scientists, including Benetti, have been at it on and off for about 30 years. Unlike some tuna and grouper-snapper species, mahis are not currently overfished, so there has been no urgent push to develop techniques to farm them. But that could change with increased consumer demand and fishing pressure. So last year, Benetti decided to “revisit” the species, looking for ways to raise them profitably and sustainably.

Getting the marine lab rats to reproduce has not been a problem. Beginning with a bull and several cows caught last fall off Miami by research assistants John Stieglitz and Ron Hoenig, the dolphin quickly spawned and their offspring have done the same. Now a couple thousand fish — from tiny larvae to the apex 20-pound bull nicknamed Guppy — occupy several tanks.

“They are the most prolific fish in the ocean,” Benetti said. “In five to six months, they’re already spawning. They spawn every day.”

But the downside to life in the fast lane is that they die young, he said — most before the age of 2 years.
The biggest challenge to raising dolphin has been to satisfy their enormous appetites, which unfortunately drives them to cannibalize one another.

Younger fish are fed pellets containing meal and oil made from other fish. As they grow larger, they get hunks of sardine and squid. But when they get hungry between feedings, even the fingerlings have been observed ganging up on their weaker brethren and devouring them like pack animals.

“They beat the cobia in nastiness,” Benetti said.

The scientists are looking for ways to replace fish meal and oil with a more economical and sustainable feed for their charges. Developing that technology would make dolphin more attractive to prospective farmers.
Meanwhile, Benetti’s 25 students and research assistants — many of them recreational anglers — seem enthusiastic about the dolphin project.

“They’re fun to work with,” Stieglitz said. “We’ve been doing cobia for so long, it’s a nice change of pace. And we enjoy the brood stock captures.”

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