Mercury in Fish Caught by New Jersey's Coastal Anglers

by Joanna Burger and Michael Gochfeld

(from Jersey Coast Anglers Association May 2008 Newsletter)


For years we have been conscious of our diet, selecting fish for the many healthful nutritional benefits, even before the specific details of omega-3 fatty acids were common knowledge. Yet fish, particularly those species high on the food chain, accumulate contaminants which can jeopardize health. What to do? How to choose? We have spent the last twenty-five years studying mercury, lead and cadmium in fish, often near heavily contaminated sites, like Superfund dumps, Department of Energy nuclear weapons sites, and contaminated harbors and bays. For the last three years, however, we have been working with the Jersey Coast Anglers Association to examine levels of mercury in fish caught by recreational fishermen along the Jersey shore. It is an exciting project because recreational fishing is an important cultural and economic part of New Jersey. Fish, however, are the only major source of methylmercury exposure for the general public.

Fishing is Important for New Jersey Residents

Fishing is important to New Jersey, both as a commercial and recreational enterprise worth about $2 billion annually, as well as contributing to the $16 billion dollar coastal tourism income. Fish are an important source of protein, and fishing is a popular pastime all over the World, including our urban areas, such as the New York-New Jersey metropolitan area.

Over the years our studies, often involving interviews with anglers fishing along the Jersey shore and in the NY-NJ harbor, have shown that:

  1. People fishing along our coasts eat most of the fish they catch, and they eat more fish than EPA or FDA recognize as “typical” for Americans.
  2. There are ethnic and cultural differences in the information base and compliance with fish consumption advisories issued by the state (mainly for freshwater fish).
  3. People generally believe that fish are safe to eat, but have little information about mercury in the specific fish they eat.
  4. Many people would eat more fish if they only knew which ones were safe to eat.

Benefits and Costs of Eating Fish

There are nutritional benefits to eating fish, particularly as an alternative to red meat. Fish offer high quality protein, low in cholesterol, and have omega-3 polyunsaturated fatty acids (PUFAs) which promote cardiac health and baby development. Over the past 15 years, people have responded to the health benefit messages by eating more fish. Adults who eat fish frequently (once a week or more) generally have lower cholesterol and a reduced risk of heart disease compared to those eating fish less than once a month. Likewise, pregnant women who eat fish are less likely to have low birth weight babies than are those who don't eat fish.

However, contaminants in fish, such as mercury and PCBs, can cause health problems, especially in unborn babies and children. And the mercury in fish counteracts some of the benefits of the PUFAs. Despite the interest in self-caught fish freshwater fish, little attention has been directed at salt water fish or at the fish that are commercially available in supermarkets and fish stores, the source of fish for most New Jersey residents. In some cases, important recreational fish, like Bluefish, are also available in New Jersey fish markets and supermarkets.

Government Agencies and Fish Consumption Advisories

Different state and federal agencies issue fish advisories telling people what fish to avoid because of high contaminant levels. The Food and Drug Administration issued advisories based on methylmercury that suggested that pregnant women and women of childbearing age who may become pregnant should avoid eating four types of marine fish (shark, Swordfish, King Mackerel, and Tilefish), and should limit their consumption of all other fish to just 12 ounces per week (see FDA.gov website). While this is helpful, it does not tell people what fish they can eat safely. The FDA has set an Action Level of 1 ppm of methylmercury. Fish that exceed this level could be seized in interstate commerce, although since FDA does not routinely test fish, no seizures are occurring, even though we have found exceedances in some fish samples.

People who fish or like to eat fish are interested in what fish are low in mercury – which is a different question from the government's advice on which fish are high in mercury. It is easy to guess which fish are at the top of the food chain and will be high in mercury (shark, swordfish), but not whether medium-sized predatory fish (Bluefish) or bottom dwellers (flounders) have dangerous levels of mercury. Also, age and size are important because older fish have longer to accumulate mercury than do younger fish. Some very large fish (like a 100 pound Halibut) are younger than some smaller fish (such as Rock Fish, which are only a foot long). Guessing isn't good enough!

Our research with mercury levels in fish purchased in supermarkets indicated that the levels in some fish are sufficiently low as to provide no risk no matter how much is eaten, while this is not the case for other species. Fresh tuna steaks had the highest levels, and were in the range that could potentially provide health problems for unborn babies (see JCAA article on Toxins in Fish, January 2005). People who want to eat fish more often need to know the relative levels of mercury in fish so that they can make their own decisions. Our study is aimed at providing this information.

The FDA publishes information on the mercury content of a variety of fish. See http://www.cfsan.fda.gov/~frf/sea-mehg.html.

Our Study of "Mercury in New Jersey Coastal Fish"

Our objective was to determine mercury levels in fish commonly caught by recreational anglers in New Jersey's bays, estuaries and the ocean. We enlisted both individual anglers and clubs from the Jersey Coast Angler’s Association to help us collect a range of different species of fish, with a range of sizes of each type of fish. In many cases, we went to fishing tournaments, and took a small sample (about the size of our thumb) from each fish at the time of weigh-in, and we also went out with DEP sampling boats to obtain some smaller fish for comparison with those that fit the legal size limits. This study was unique because it involved collaboration between anglers and scientists, between fishing clubs (JCAA) and scientists, and it involved fish that people are actually catching and eating (rather than those caught by electroshocking, seines, or other trap methods.

Mercury was then analyzed in our laboratory at Rutgers University and the Environmental and Occupational Health Sciences Institute.

Findings to Date on Mercury Levels in New Jersey’s Coastal Fish

Our two primary interests are determining 1) the levels of mercury in different species of coastal and estuarine fish, and 2) whether mercury levels increase with the size of the fish. Armed with this type of information, people can select what species of fish to eat. There are, of course, subtleties, such as how much variation in levels of mercury is there within each species, and do the mercury levels vary by season.

Overall, mercury levels vary by fish species, with some being higher than others. Mako Shark had the highest levels, followed by Striped Bass, Bluefish and Bluefin Tuna. The lowest levels were in Bonito, Dolphin, Weakfish and Porgy.

FishMercury Levels% of Fish Above 0.3 ppm% of Fish Above 1.0 pp
Mako Shark2.099688
Striped Bass0.47775
Bluefin Tuna0.43750
Black Sea Bass0.1700
Yellowfin Tuna0.1330

In general, mercury levels increased with the length (and weight) of the fish for Bluefish, Mako Shark, Striped Bass and tuna. That is, larger fish had higher mercury levels than smaller fish, suggesting that given a choice, it is better to eat the smaller fish. The figure below shows the increase in mercury with size for Bluefish and Striped Bass. The numbers under the Bluefish line indicate the approximate age of the fish in years.


We don’t measure omega-3 PUFAs in our laboratory, but values have been published for a number of species. In general the ideal situation would be to eat fish that are high in PUFA but low in mercury, for example, Salmon.

Next Steps

We are continuing to analyze fish, concentrating on figuring out whether mercury levels vary by season or by location along the coast. Both aspects require increasing our sample sizes to be able to distinguish differences. We want to know whether levels are higher in the spring or fall for Bluefish, for example. We are also examining the relationship between mercury levels and selenium because there is some indication that selenium is protective against the effects of mercury in people and other organisms that eat the fish. So far the data indicate that selenium levels are relatively constant in New Jersey coastal fish, which might suggest another reason to eat smaller fish.



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