A fish farm. Courtesy Nashua National Fish Hatchery

A fish farm. Courtesy Nashua National Fish Hatchery

11/13/2007

Fish Hatcheries: Silver Bullet or Red Herring?

by Lauren Cahoon

We’ve done it again. The ocean’s fish, a once plentiful and healthy food source, is now depleted and can be hazardous to eat. With wild fish burnt out, it may be time to grow our own. While chicken and pig farms are smooth-working mega-industries, fish farms haven’t reached the same level of efficient success. I set out to the MIT Sea Grant’s fish hatchery to find out why.

Tucked near the docks of fishing- town Gloucester, Massachusetts, is the MIT hatchery, a testing ground to see if certain species fish can even be farmed at all—many species simply can’t adapt to the artificial environment. The current try-outs were winter flounder and black sea bass; both are favored sea-food entrees and both are populations dwindling in the ocean.

Brandy Moran Wilbur, director of MIT’s hatchery, agreed to give me a tour of the operation. As I entered an underwhelming cement-floored room of the hatchery, I heard the purring of the filtration which takes care of organic pollution—a flaw that has plagued traditional fish farms. When fish are caged in bodies of water, the large amounts of feces and uneaten food can build up and change the natural environment. Here, however, the fish reside in several tanks connected by plastic piping that takes the dirty water through a series of filters. These cleanse the water of any particles, organic waste, or nasty microorganisms. Ninety-eight percent of this recycled water is shot back into the fish tanks, with 2% (cleansed) harbor water combined into the mix.

It’s an elegant system; it solves the problem of pollution, and also means farming marine fish can happen away from the ocean. But for a fish farm that’s larger than a garage, it’s expensive. Dr. Wade Watanabe, aquaculture program coordinator at the University of North Carolina -- Wilmington, runs a much larger closed system, and noted that buying and maintaining all the tanks, pumps, and filters is certainly more expensive than just caging fish up in the ocean. Huntting Howell, director of the coastal marine laboratory at the University of New Hampshire, thinks it’s too difficult to build the system on a large commercial scale, and stated that the few large fish farms that have built a closed system can barely afford it.

Besides the equipment being expensive, the livestock can be finicky. Fish, especially young ones, are sensitive to everything; food type, current, temperature—even light. So despite a food-filled, predator-free environment, the fish are prone to massive die-offs when any part of their environment changes. Thus, survival rates in most hatcheries reach only around 10-20%. This is still an improvement from survival rates in the wild, which hovers at only a fraction of a percent.

The younger fish appear truly delicate, the flounder larvae resembling paper-thin coins at the bottom of their tank. The older fish look heartier, the striped bass, darkly colored, swim gracefully around their tank, the winter flounder lie overlapped on the bottom like mottled pancakes. They all swarm expectantly to the surface as I draw near, expecting their food of inert pellets made of ground-up anchovies and bait fish.

Feeding is probably the biggest environmental issue in aquaculture. Nearly all hatcheries that raise carnivorous fish use bait fish like anchovies as feed, a system that critics call “feeding songbirds to eagles”—depleting one population to feed another. However, Howell says this attitude is incorrect and unfair, that most fish meal is produced for livestock and pet food anyway.  Also “(bait) fish are among the most abundant species in the world…People should be worried about the 1 million pounds of herring that’s used for lobster bait. But they don’t complain because most people are happy to sit down to a lobster dinner.”

Still, the over fishing concerns, combined with growing fear of mercury contamination caused aquaculturists to investigate a veggie diet for farmed fish, experimenting with soy or corn substitutes to see how much the carnivorous fish will stomach. Unfortunately, even if the fish accept a veggie diet, they don’t grow as fast, and tend to lose their tasty flavor. Watanabe is working to develop a ‘finishing diet’, a final meat-based meal that hopefully pumps the flavor back into the fish’s body before it goes to market.

Like any new industry, fish farming needs time to puzzle through the inevitable kinks. As research outfits, like MIT’s hatchery, continue to piece together what marine fish need, we may get closer to having our fish and eating them too.