182 Sharks: The Animal Answer Guide
Is it safe to eat sharks?
Generally yes (although not for the sharks). It all depends on the species
and especially the place where it was caught. That latter fact is seldom if
ever included on the label.
Sharks are top predators. This vaunted position in the food chain car-
ries with it nutritional costs. Many chemical pollutants do not break down
in animal tissues, meaning predators accumulate the dosage of their prey
with each meal, adding to their “body burden” of pesticides, PCBs, PBDs,
flame retardants, pharmaceuticals, heavy metals, and numerous other haz-
ardous substances. Because sharks are predatory and live a long time, it is
not surprising that their muscle, fat, and liver contain high levels of some
pollutants.
Mercury is one such toxin. Sharks in some places have been found to
contain mercury levels that exceed the safe level of one part per million
(1 ppm) set by the U.S. Food and Drug Administration (FDA), and the
more stringent (and precautionary) level of 0.3 ppm set by the U.S. En-
vironmental Protection Agency (EPA). In Florida, fully one-third of the
sharks sampled exceeded FDA standards. Shortfin Makos off New Jersey
contained mercury levels of 1.8 ppm, almost double the FDA standard and
six times higher than the EPA standard. Blue Sharks, Smooth Dogfish and
Spiny Dogfish, three other species that find their way into seafood shops
and restaurants, have also been found with levels of mercury that exceed
the EPA standard. Some species, such as Smooth Dogfish and Spiny Dog-
fish, accumulate mercury as they age, rather than metabolizing it, meaning
that larger individuals tend to be more contaminated. Fully 70% of shark
muscle samples from dozens of species were at or higher than the maxi-
mum allowable limits for human consumption in the United States and
Canada.
The liver is the major organ of decontamination in vertebrate animals,
serving to remove toxins from an animal’s blood stream. It is therefore not
surprising to find elevated levels of pollutants in shark livers. Large, long-
lived open-water and deepwater sharks appear to have the highest con-
centrations of liver contaminants; these include organochlorine pesticides
(OCPs), which are synthetically manufactured chemicals like DDT, chlor-
dane, dieldrin, and lindane. High levels of DDT and other OCPs have
been found in the livers of Gulper Shark (Centrophorus granulosus), Blue
Shark, and especially Greenland Shark. Both juvenile and adult White
Sharks off South Africa have high DDT concentrations, not in their livers
but in their muscle.
A study published in the Marine Pollution Bulletin found that Greenland
http://www.ebook3000.com