Here’s a thorough and thoughtful email response to me by Seagrant Educator Dan O’Keefe of Michigan State University Extension to my post “Fishing In New York” I recently made on the safety of eating fish from New York City’s surrounding waterways. Mr. O’Keffe has given me his written permission to put his response on my blog:
Mr. O’Keefe responded:
“Not all contaminants are created equal. The health implications of mercury are better understood than PCBs and dioxins, and contaminated fish have led to demonstrable health effects in the case of mercury. Furthermore, PCBs and dioxins are fat-soluble and can therefore be reduced in sport-caught fish by skinning fillets, trimming dark meat and fat, and cooking. This is not the case with mercury. Studies have shown 40-80% reduction in PCBs due to proper preparation.
When contaminant levels are measured in fish a variety of methods are used, but often the whole fish or skin-on fillets are ground up before processing. This is not reflective of how most people prepare and eat their catch (i.e., raw and uncleaned or untrimmed). Again, this is more of an issue for PCB/dioxin than mercury which is present in all body tissues.
So, as foragers where does this leave us? My take is that the health department guidleines are a useful tool for weighing the RELATIVE (not absolute) risk of eating fish based on 1) species of fish, 2) size of fish, and 3) body of water. They also clearly show that women of childbearing age and children are more at risk from developmental or reproductive effects and should be more cautious.
In practice, I use this information on a regular basis. It works out well to give the kids the small sunfish fillets while eating the catfish myself. As far as locations, the data on fish contaminant levels clearly show that fish from our clear-water Great Lakes are much more contaminated than fish of comparable size/species from most inland (and often muddy-water) rivers. That works out well for me as a river fisherman, but it goes against “common sense” that assumes muddy river fish are dirtier than big lake fish.
This is where checking your own state booklet can help a lot. The NYC book shows the Lower Bay, Ocean, and Sound waters to be much better than other areas. Also, note that it states most marine species are not listed at all because they are less contaminated. Too often, people just see the “DO NOT EAT” recommendations for certain fish in certain areas and then assume that everything is off-limits. When it comes to mecury in particular you are better off catching and eating small inshore species of marine fish (croaker, grunt) than eating commerial-caught top predators like tuna, swordfish, and shark.
From an ecolgical perspective this works out well. Small, abundant, and often-overlooked species (even invasives!) are often healthier than commercially-exploited top predators that are declining in oceans worldwide. Even within a species, the smaller individuals are less contaminated than the older “superspawners” that perpetuate the population and ensure high-quality genetics for the next generation.
Wow, and I thought I might be able to provide a concise answer…”
Seagrant Educator Dan O’Keefe
Michigan State University Extension