When I was a kid growing up in Seattle, my favorite restaurant treat was a heaping plate of deep fried popcorn shrimp; in fact it was the only fish I’d eat.  In college I sustained myself cheaply on tuna fish sandwiches.  Since then I’ve developed a taste for a wide variety of seafood and freshwater fish.  Unfortunately, eating fish these days is not quite the carefree event it was in my childhood and college years.

I realized as I started researching this topic that I would be able to give only an overview to what is a complex subject.  Much of the information I am presenting comes from the Monterey Bay Aquarium and the Environmental Defense Fund websites. 

Presently, there are two main concerns with regard to our eating fish:  sustainability and human health. 

Let’s start with sustainability.  After all, if we lose the world’s fish stocks through environmental degradation and harmful fishing practices, the health concerns about eating fish will no longer be an issue.

What is harming our fish and other aquatic life?

Overfishing.   As the human population has grown so has the demand for fish.  The ocean, just as the land, is not a limitless larder.  The fishing catch between 1950 and 1994 increased 400%.  Eighty-two million metric tons of fish are caught every year.  If you are a fisherman, try to compare that figure with your normal yearly catch.  Harvesting more fish than can repopulate themselves eventually depletes the stores of fish until they can no longer support a fishing industry.  This has already happened with Atlantic cod, once thought to be an unlimited supply of fish. Bluefin tuna are now in decline because of the worldwide demand for sushi. When one species is fished out fisherman look for other species to catch.  Slowly, but surely we are depleting the oceans of fish and other aquatic life.

Bycatch.  When a fisherman nets species he did not intend to catch it is called “bycatch.”  These fish are thrown out dead, or dying.  It is estimated by the United Nations Food and Agriculture Organization that one in four animals caught in the sea is bycatch.  For shrimp caught by trawlnet, the bycatch is 2-10 pounds of marine life for every pound of shrimp.

Habitat destruction.  The destruction of coastal wetlands and the pollution of bays has damaged many of the habitats of those fish we used to find on our dinner plates.  Fertilizers, pesticides, sewage, oil, and everyday chemicals all contribute to habitat destruction.  Half the world’s population and most of the world’s largest cities are located next to the ocean.  The impact of such enormous human populations living in close proximity to vulnerable ecosystems is staggering.

Destructive fishing techniques.  Techniques, such as bottom trawling and dredging, scoop up everything in the net’s path, including the ocean floor.  Just as we’ve discovered with some clear-cutting of old growth forests, or mining practices, once the ecology of an area is destroyed it can take centuries to return to something like it’s original state.  Trawlers have been known to pull up seven hundred year old coldwater corals.  Those environments cannot be replaced except over a very long time and with their loss go all the sea life that depends upon them.  Trawling happens all over the world every single day.

What health concerns are associated with eating fish?

Pollution.  Our waterways, both fresh and salt water are contaminated with a witch’s brew of chemicals, such as mirex, mercury, dioxin and PCBs.  As these chemical toxins flow down through our streams and rivers to the ocean, or are washed down from the air by rain, they are ingested or absorbed by the aquatic and bird life found in and around water.  Toxic substances can reduce fish and amphibians ability to reproduce or can change their DNA producing malformed fetuses.  When we eat fish we, too, ingest these same chemicals to a greater or lesser degree depending upon the type of fish and the environment from which it came. 

Common toxins in fish.  In my research I discovered four chemicals commonly found in fresh water and ocean fish:  mercury, mirex, dioxin and PCBs.

Mercury: Mercury is a naturally occurring element that has been released in greater quantities to the environment by human activities such as industrial processes, coal-fired power plants, incineration of substances containing mercury, and in places such as in health care facilities and even in our homes.  Anyone who has fished Lake Ontario has heard about mercury warnings.  Lately, it has also been found in sushi (Bluefin tuna) and in canned tuna (primarily white tuna). Mercury at toxic levels can damage the nervous system.

Mirex:  Originally developed as an insecticide it was banned by the United States Environmental Protection Agency in l976.  It has been found to cause cancer in laboratory mice and rats.  The onset of toxicity and mortality is typically delayed.  It is particularly damaging to crustaceans.

PCBs:  PCBs were developed as coolants and lubricating fluids for power line transformers and capacitors; think the power pole outside your house.  Among other applications it has been used as an additive in paints and cements, pvc coatings, lubricating oils and wood floor finishes.  PCBs have been found to be carcinogenic and its use in the United States was banned in 1979.  It is still found in enclosed systems, such as transformers and capacitors. The upper and lower Hudson River is still being cleaned up from the dumping of millions of tons of PCBs.  The health effects on humans range from skin rashes to possible liver damage and a lowered immunity.  Children show poor cognitive development.  Animals ingesting PCB contaminated food show liver damage and mortality.  PCBs contamination has been found worldwide.

Dioxin:  Dioxin is a small family of chemicals formed as byproducts of materials, such as pesticides.  During the 1960s, when pesticide manufacturing was in full swing, dioxin pollution became widespread.  Only later did scientists discover it was carcinogenic.  Dioxin mimics the actions of hormones.  As it penetrates the cell wall it changes DNA so that messages sent by DNA are no longer normal or reliable.  Science does not yet understand the relationship between such changes in DNA and disease.

What stunned me was to discover that all of these toxins are found in greater or lesser amounts in most of the fish that we eat.  They all accumulate in biological organisms and are slow to degrade.

Is it safe to eat any fish?  That depends on several factors such as age, sex, if you are a woman of childbearing years, whether your immune system is compromised, the type and amount of fish you eat and where it comes from.  Fortunately there are organizations that provides information to help you make good choices.  Both Monterey Bay Aquarium and Environmental Defense Fund websites publish checklists of which fish are safe and sustainable and which are not safe.  To download a copy of a pocket guide to safe seafood selection go to:http://www.montereybayaquarium.org/cr/cr_seafoodwatch/download.aspx.

What about fresh fish from Lake Ontario?  In a Canadian report done by Environmental Defence (“Up to the Gills:  2009 Update on Pollution in Great Lakes Fish.”) certain fish in the Great Lakes were found to contain high levels of toxins and some were deemed unfit for human consumption.  Information from the New York State Department of Health recommends that woman of childbearing age and children under fifteen should eat no fish from Lake Ontario.  Others can eat the fish, but it is recommended that you limit it to no more than once a month.

What can we do?

-Get informed abut safe and sustainable fish and tell everyone you know.

-Ask your fish seller and the restaurants you patronize where their fish comes from.

-Buy North American fish.  U.S. and Canadian fisheries, as well as those in New Zealand, are the most highly regulated in the world.  Other sources are not so reliable.  For example, it was found that tuna steaks from Vietnam had been treated with carbon monoxide, so that they would look fresh even when they weren’t.  Farmed shrimp from Southeast Asia are raised under less than sanitary conditions.  Buying North American supports fisheries that are safe and sustainable, and it keeps fishing jobs at home.

-Purchase fish from a safe and sustainable list, such as those published by Monterey Bay Aquarium or the Environmental Defense Fund.

Your turn:  Do you know if your favorite fish is safe to eat?  Is it caught or farmed in a sustainable manner?

Resources and inspirations:

www.montereybayaquarium.org  (Seafood watch pocket guides by U.S. location).

www.edf.org   (Seafood selector, health alerts and sushi selector).

www.health.state.ny.us (Health advisories).

www.environmentaldefence.ca ( To find the report “Up to the Gills”).

“The Empty Ocean,” by Richard Ellis.

Next week:  New appliances for old?