What species of mackerel is in the common canned mackerel -- and, if
it isn't king mackerel, do cautions about mercury in king mackerel
apply to common canned mackerel?  I eat a lot of canned mackerel for
the healthy omega-3 fatty acids in them, and they are cheaper than the
known safe canned fish -- salmon and sardines.  I keep hearing
warnings about mercury in mackerel, but the warnings always specify
KING mackerel.  I can't find out what kind of mackerel is in the
canned mackerel I buy, but I've used a half dozen brands and they all
taste and look exactly the same.  If the canned mackerel were so
dangerous, I'd expect health authorities to specify CANNED mackerel in
addition to, or instead of, KING mackerel.  I hope your answer can
help me choose wisely.

curioz...

From what I can find, you're in no danger.

As you noted, King mackerel is the dangerous variety, as noted
in this Texas Department of Health news release in 1997:

"The advisory recommends not eating king mackerel longer than 43
 inches. It limits consumption of king mackerel measuring from 37
 to 43 inches in length to one eight-ounce serving per week for
 adults and one per month for children and females of childbearing
 age. The advisory does not restrict consumption of king mackerel
 under 37 inches."

[...]

"The advisory does not apply to canned mackerel, a different
 species of mackerel."
http://www.tdh.state.tx.us/news/b_new135.htm


Likewise, this page from BabyCenter.com notes the following, in
addressing the diets of pregnant women:

"According to the FDA/ EPA guidelines, you should also limit
 yourself to 12 ounces a week (about two servings) of canned
 "light" tuna and other cooked fish. Once again, our
 recommendations are more protective ? eat fewer than 8 ounces
 a week of canned "light" tuna. And you should completely
 avoid shark, swordfish, king mackerel, and tilefish (also
 called golden or white snapper), tuna steak (fresh or frozen),
 orange roughy, Spanish mackerel, marlin, and grouper because
 these fish are at the top of the food chain and contain the
 highest levels of mercury."

[...]

"There are plenty of other tasty varieties ? salmon, rainbow
 trout, and canned mackerel, for instance ? that contain low
 levels of mercury and are high in healthy fats. The FDA
 considers these fish safe for pregnant women to eat twice a
 week."
http://www.babycenter.com/expert/pregnancy/pregnancynutrition/2657.html


This page on NutraJoint notes that the variety of mackerel
which is canned is Pacific jack mackerel (also called horse
mackerel):
http://www.nutrajoint.com/vf/healthnotes/HN_live/Food_Guide/Mackerel.htm


This summary of a 2004 study by the Institute of Food
Technologists notes that, when canned tuna, salmon and 
mackerel were tested, mackerel had a relatively low 
concentration of mercury:

"Mean mercury concentration in tuna, salmon, and mackerel
 were 188, 45, and 55 ppb, respectively."
http://ift.confex.com/ift/2004/techprogram/paper_25801.htm

The full study is available in this document file:
http://listproc.ucdavis.edu/archives/seafood/log0307/att-0031/01-Report2003.doc

Happy eating!

sublime1-ga


Additional information may be found from further exploration
of the links provided above, as well as those resulting from
the Google searches outlined below.

Searches done, via Google:

mercury "king mackerel" "canned mackerel"
://www.google.com/search?q=mercury+%22king+mackerel%22+%22canned+mackerel%22

mercury ppb fda "canned mackerel"
://www.google.com/search?q=mercury+ppb+fda+%22canned+mackerel%22