Aquaculture for all

New Fish Farms Move from Ocean to Warehouse

US - At the University of Maryland Biotechnology Institute's Center for Marine Biotechnology, John Stubblefield and his fellow researchers are not only altering nature, they are creating what may be the next generation of seafood, write Ben Block.

Earlier this week, Stubblefield walked past the blue tanks of striped bass, Atlantic sea bream, and cobia stored inside a Baltimore, Maryland, laboratory.

"In this tank, it's spring in May. This tank it's spring in September," he said.

The experiment uses city-supplied water and a complex microbial filtration system to raise a few hundred fish completely indoors. Yonathan Zohar, the center's director and the study's leader, said it is the first indoor marine aquaculture system that can re-circulate nearly all of its water and expel zero waste.

"I'm a strong believer that in 20 years from now, most seafood will be grown on land. It can go to the Midwest, it can go into the inner city, it can go wherever," Zohar said.

Sustainable answer

If Zohar's team proves the system could become economically competitive with current marine fish farming techniques, Zohar says he may have found a sustainable answer to the world's growing fishery crisis.

Some estimates say as much as 90 percent of edible marine fish may disappear by 2048. The most common alternative is through fish farms that raise ocean-captured fish in coastal nets called net pens. Marine aquaculture expanded about 10 percent each year between 2000 and 2004, according to the UN Food and Agriculture Organization, with recent growth especially in the Mediterranean Sea around Greece and Turkey. However, net pens pollute coastal environments with waste and antibiotics, fish escapees pose a threat to the diversity of wild fish populations, and diseases can spread easily through net-pen fisheries.

Some nations are responding to net-pen pollution by closing troublesome operations. In Israel, for example, the government has called for the removal of 2,700 tons of Red Sea net pens by June due to damage to nearby coral reefs. Zohar spent a decade developing those same net pens when he worked for the Israeli National Center for Mariculture before relocating to Baltimore in 1990. He says his land-based fish farming system is an improved alternative. "They are disease free, pathogen free; they are contaminant free; they are toxin free," he said. "We tested them. They're as clean as you can get."

Zohar's team is primarily raising cobia, a highly priced fish found off the eastern coast of North America and in the western Pacific Ocean. Cobia do not swim in schools, making them difficult to catch in large amounts, but when raised in an aquaculture operation they become a valuable food product. The lab is growing the cobia faster and more efficiently than if they were in a net pen, researchers say. "They grow like crazy-about one pound per month! That's double most species," said Stubblefield, the lab manager.

Most fish do not reproduce in captivity due to the absence of environmental clues, so forcing reproduction was the team's first hurdle. In addition to altering the water temperature, lighting, and salinity levels, Zohar invented a pellet that mimics the hormone necessary to spur a fish's natural reproduction process. The pellet is now being used in aquaculture and conservation efforts for various global fish species.

From the start, Zohar's lab committed to creating a sustainable, low-impact aquaculture system. They say that 99 percent of their water is recycled, with the only losses due to evaporation. An open-air system filled with microbe-covered, honeycomb-shaped plastic first detoxifies ammonia from the water. The water then flows into an oxygen-free system where different bacteria absorb the nitrogen. For the solid fish waste, a separate filter uses microbes to convert the sludge into methane, creating a clean-burning biofuel. The goal is for 10 percent of the aquaculture's energy needs to be offset by the methane byproduct, Zohar said.


Environmental Defense senior scientist Rebecca Goldburg visited Zohar's lab several years ago while serving on the Pew Oceans Commission. She said that while the system offers potential, it still has trade-offs. "When you grow fish in an indoor tank, it takes a fair amount of infrastructure and it can take a fair amount of energy," said Goldburg, an ecologist who specializes in aquaculture systems. "I'm hesitant to advocate a one-size-fits-all solution."

Also, the fish being raised are carnivorous, so feeding them requires the input of other fish that are caught or farmed, likely in a less sustainable manner. Several research efforts around the world, including Zohar's lab, are studying whether an algae-based food can replace the food pellets currently used, which are about 40 percent fish meat.

So far, investors have been hesitant to replicate Zohar's aquaculture due to fears that the system cannot compete with net pens. But as seafood demand increases and supply dwindles, Zohar remains confident. "Once the first couple are up and running, this thing is going to spread like fire," he said.

Ben Block is a staff writer with the Worldwatch Institute who covers everything environmental for Eye on Earth. .
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