Earth & Sky

For more information about ocean-friendly seafood, please visit the following websites:

The Blue Ocean Institute’s Guide to Ocean Friendly Seafood

The Monterey Bay Aquarium’s Seafood Watch Program

One Fish, Two Fish, Crawfish, Bluefish – The Smithsonian Sustainable Seafood Cookbook has over 150 recipes from top chefs from throughout the United States for U.S. fish and shellfish species fished or farmed in an ecologically sound manner.

If you enjoyed today’s show, you’ll find more information about aquaculture and ecosystems at the following websites:

Pew Charitable Trusts link to the Science report cited below: Global Assessment of Organic Contaminants in Farmed Salmon (Jan 2004)

Salmon of the Americas

The Environmental Working Group’s information page on PCBs in Farmed Salmon

Articles:

Salmon survey stokes debate about farmed fish, by Erik Stokstad. January 9, 2004. Science Magazine. Vol 303 pp.154-55.

Global Assessment of Organic Contaminants in Farmed Salmon. Hites et al. January 9, 2004. Science Magazine. Vol 303 pp 226-29.

Scientists back toxic salmon study; Independent experts say results are undeniable? after industry blasts report for orchestrating food scare, by Rob Edwards January 18, 2004. Sunday Herald

Health benefits of salmon likely outweigh risks from pollutants, by Micheal Woods, January 18, 2004. The Toledo Blade.

Author’s Notes:

It’s important to note that some types of fish farms are relatively benign. Catfish, for instance, are raised in closed systems. It’s also important to remember that aquaculture is a huge and growing industry that helps feed many, many people. Luckily, the links to better seafood choices, above, help distinguish between the more and less damaging types of fish farms.

Still, the creation of some farms, like some shrimp farms, can eliminate critical nursery habitats like mangrove swamps. Others, including oceanic net pens, release nutrients into marine ecosystems. These nutrients can change the fundamental structure of the local marine community. Furthermore, some species of farmed fish can escape and interbreed with wild fish. Conservation scientists worry that this, too, could undermine the health of wild populations.

Remember, too, that like industrially raised beef, chicken, and pork, many farmed fish are heavily dosed with antibiotics and hormones to keep them healthy in the highly crowded conditions in which they are grown.

Then there’s the recent research showing that farmed salmon have higher levels of environmental pollutants than wild caught salmon. Farmed fish eat as lot fish food. And a lot of that fish food comes from smaller species of wild fish. If these fish are harvested from polluted areas, then they will concentrate contaminants up the food chain and into the bellies of the farmed fish to which they are fed.

In this particular study, farmed Atlantic salmon from Northern Europe and North America were more polluted than fish grown in South America. Wild Pacific salmon generally had lower levels of pollutants, although some populations had levels comparable to some farmed salmon.

One of the things the aquaculture industry is working on right now is developing fish foods that are derived from sustainable, vegetarian sources like soybeans. This would mean less toxic accumulation and it would also relieve pressure on wild populations harvested as fish food.

There’s no easy answer when it comes to fish. Many fish, like salmon, are very healthy to eat and offer a generous supply of heart-healthy omega 3 oils (But so do walnuts and flax oils). Some nutritionists argue that the benefits of eating fish like salmon far outweigh the risks of eating contaminated fish (Although they are less likely to argue this for pregnant or nursing women or young children).

What’s more, environmental contaminants are now pervasive throughout the world. Most of the food we eat is polluted at some level. Because of “bioaccumulation,” meats, dairy products and fish tend to have higher levels than vegetable sources of food. That’s because animals consume a lot of vegetable and animal matter. And if that matter contains chemicals that “stick,” or bioaccumulate, then the animal ends up getting far higher concentrations of that chemical than a similar amount of plant material. For example, it takes 17 pounds of corn to grow one pound of beef.

Concerned fish lovers would do well to use the available seafood selectors to help them decide which sorts of fish to buy. If you want the fish that are the most sustainable and least damaging to the environment pick those grown in relatively benign fish farms, such as catfish. Or shop carefully for wild-caught fish that are from well-managed, sustainably harvested populations, like certain wild-caught Alaskan salmon. These might cost more, but the cheaper farmed fish have many invisible costs.

Highlights from interview with Dr. Carl Safina:

Aquaculture, at first glance, appears to hold the promise of producing food for people while lessening pressure on natural populations of wild fish. We don’t see things working this way currently. Why?

First: There is no case where farming has resulted in less pressure on wild stocks or populations. We are still fishing wild fish very heavily. Furthermore, most “fish food” for farmed fish consists of other wild caught fish. So, to feed many farmed fish, wild populations are fished. Many wild populations are still over fished, despite the availability of farmed fish.

Second: Despite being the most extensively farmed types of seafood, wild populations of salmon and shrimp continue to have as much fishing pressure as ever before.

One perverse result of this may occur in Alaska. There remain a few wild populations of salmon that are well managed and sustainable (that is, the population is not being over fished and depleted). Here the rivers are not destroyed and the fish, and their environment, are relatively pristine. But because of price pressure from farmed salmon, the fisheries are becoming economically unsustainable. Thus one of the few sustainable, well-managed wild fisheries left, will not be viable because of economics due to salmon farming.

But farmed salmon (and other fish) pose risks. They can damage natural habitats, escape and mingle with wild fish, and may be contaminated with toxins (although wild fish can also be contaminated).

Farming fish can also destroy natural habitats and make them unrecoverable for future generations of wild fish. Like transforming natural areas into cities or farms, a land-based fish farm can permanently destroy a wild habitat. For fish farms in the ocean, it is possible to recover that habitat but these, too, have problems. They add a tremendous source of nutrients to the area, and farmed fish do escape from so-called ocean pens. They can interbreed with wild fish.

Basically, what we know about farming fish is all rather negative. But there are things consumers can do to make informed choices. Learn about what fisheries are sustainable and base your purchasing decisions on those. Choose your fish from well-managed, sustainable fisheries rather than from a monoculture (farm) that was previously wild habitat.

There are a few “good” ways to farm fish, such as when the farm is enclosed and re-circulating on land, or integrated with other farms such as with rice culture in water.

Finally, there may be health risks associated with eating certain farmed fish. Many farmed fish are fed a diet of other processed fish. The “fish food” is caught from areas around the world, and depending on whether the waters were contaminated, the fish, too may be contaminated. Thus, the fish food may increase the level of “biomagnification” of toxic chemicals in farmed fish (not to mention other farmed animals like chickens and pigs which are also sometimes fed processed fish). Wild fish can also have contamination problems, but as with farmed fish, it depends on where and how contaminated the food they eat is itself.

We expect to see more and more research on not only sustainable fisheries, but also which fish are least contaminated by environmental pollutants.

[From a follow-up conversation with Dr. Safina]

I’ve seen fish farming operations in a variety of places, a number of sights in North America, Central America, and Asia. And in general, they are sighted in places that until recently were natural aquatic habitats, natural coasts and marshes that are changed to make a farm similar to the way that a natural forest or prairie might be changed to make a farm on land. So they replace natural habitats with fish farms.

Often the habitats are right between the high and the low tide, and they’ll take the natural vegetation away and bulldoze area to make ponds that tend to be filled with water to grow fish or shrimp. Other times the animals in pens or in racks.

Often the natural habitats like marshes and mangrove areas in between the high and low tides are bulldozed to make ponds, the natural vegetation is removed, and the mud is bulldozed to make ponds to grow fish or shrimp. Sometimes floating cages are used to grow fish or racks are used to grow shellfish. And those have varying effects on the environment. Obviously, the bulldozing is the worse, floating racks for shellfish is the most benign.

Fish are not cabbages, and they don’t grow on sunlight – you have to feed them something. And mostly what we feed them is ground up fish that are caught in the ocean. So we actually have to feed more fish than what we get out of the farms. A lot of the feed is put into pellets, and fed to the fish, and a lot of it ends up falling through the cages. Also, of course, the droppings from the fish fall through the cages and collect, and are sources for pollution.

How big a problem that is varies depending on the nature operation it is. And there are actually a number of that are not bad at all – clams, oysters, muscles – they filter their own food out of the waterways. They are the easiest on the environment out of all of the changes that aquaculture cause, they are the least of it. But things like salmon farms, or shrimp farms are fed a substantial amount of fish, and they can also create a bit of a problem with their droppings, which can be quite serious, depending on the tides and the currents.

The effects on the habitats vary, the biggest direct effect is the replacement of the natural vegetation and the natural habitat with farms, and that destroys some areas. Other effects have to do with the escape of fish or the escape of diseases that are bad for the local environment and bad for the local fish, sometimes catastrophically bad.

Some of the major effects of the farms on the habitats have to do with the replacement of the natural vegetation by just scraping it away and bull dozing it, that’s the most serious effect on the natural habitats. The escape of fish that are not native to the area can have a bad effect on the local and native fish. And also diseases sometime come with fish and are sometimes incubated in fish farms and cause very serious and sometimes catastrophic problems for local populations of finfish and shellfish.

Highlights from interview with Dr. Ron Hardy:

Aquaculture is a big industry. Its products are important. The United States produces 428,000 tons per year of aquaculture products. Asia dominates aquaculture. In China, the leading producer, a whopping 32 million tons of aquaculture products come from the mainland each year. In India it is 12 million tons per year, and in Japan, 1.2 million tons per year.

Worldwide in 2003, 30% of fisheries products came from aquaculture. That’s about 50% from freshwater and 50% from saltwater fisheries. That was nearly a 10% increase over the previous year (most of that growth was in Asia). The U.S. imports about $12 billion in aquaculture products and exports about $3 billion. Thus we have a net trade deficit of about $9 billion.

Does aquaculture relieve pressure on wild populations? This is controversial. Atlantic salmon in the U.S. and Europe, for example, were already decimated by industrialization and heavy fishing pressure. It is now impossible to order a wild Atlantic salmon, but you can get farmed Atlantic salmon. The damage to the wild population happened before Atlantic salmon was heavily farmed. What’s more, the farmed Atlantic salmon provides a supply that would otherwise not exist. 99% of the Atlantic salmon that people eat comes from fish farms.

Pacific salmon are different. They are not already decimated like Atlantic salmon. Fishing pressure has been tightly regulated for 60-75 years. Farming of Pacific salmon is not as widespread as that of Atlantic salmon.

Are there ecological affects of farming on wild populations? Since there are 120-150 species raised for consumption, it is difficult to characterize ecological affects in a simple way. Catfish farms, for example, are closed systems in the Mississippi River delta. Thus, there are little to no ecological affects of catfish farms.

Shrimp are also raised in a closed system, but there has been a huge habitat loss of mangrove swamps due to shrimp pond construction. Mangroves are essential nursery ground and habitat for many oceanic species.

Marine net pens are another farming method. The fish wastes are not collected, but allowed to drift down to the ocean floor where they do have an impact on the benthic (ground-dwelling) community. The structure of that community changes when a net pen is located above it. But these farmers can move the fish in the pens around, like rotating a crop, in order to let the benthic community recover periodically.

What’s more, farmed fish can escape from marine net pens. This can hurt the farmer, since fish are lost, but it may also impact wild populations. Some farmed fish may interbreed with wild members of the same species.

A big virtue of aquaculture is that all inputs (food, water, etc.) are controlled by the farmer. Thus, it is possible for farmed fish to have enhanced nutritional value compared to wild fish.

Concerning contaminants in fish, for example, the Science article claiming that farmed fish are more polluted with PCBs and other chemicals than wild fish, it is important to remember the great health benefits of eating fish like salmon. They are an excellent source of omega-3 oils, and in my opinion (Dr. Ron Hardy) the health benefits outweigh any risk associated with possible toxins. Furthermore, the results of the study were not well reported. Some farmed fish did have high levels of contaminants, especially those from the North Sea where there has been heavy historical industrial contamination. But farmed fish from Chile and British Columbia had far lower levels of contaminants. The contamination is largely a result of the “fish food” which comes from other processed fish. In the North Seas the “feed” fish come from the polluted Baltic Sea, while the “feed” given to farmed fish in Peru is relatively clean. If we know to avoid contaminated areas, then things will improve.

Furthermore, there is a shift in aquaculture to begin raising fish using sustainable vegetarian feed sources. We are searching for ways to get proteins and lipids from vegetable sources like soybeans. This will improve the situation even more for two reasons. We can raise the vegetation in a more sustainable manner, and a vegetarian diet is likely to be far less contaminated by environmental pollutants than a fish-based diet.

Finally, don’t forget that almost all of our food is contaminated with these environmental pollutants. It’s a question of which is more polluted.

It’s important to take the concerns about aquaculture seriously. We need to improve the quality of the fish (e.g. reduce concerns about environmental contaminants) while also maintaining the health benefits of fish and reducing possible impacts on wild populations. The industry in the U.S. is relatively young, and it will evolve to become more benign.

The following people were in interviewed for today’s program. Our thanks to:

Dr. Ron Hardy
Director Aquaculture Research Institute
University of Idaho
Hagerman Fish Culture Experiment Station
Hagerman, ID

Dr. Carl Safina
President and Co-Founder Blue Ocean Institute
Cold Spring Harbor, NY