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A gigantic shark caught off Newport Beach reveals a sad reality: the waters off Southern California's coast are filled with toxins.
In a paper published in the Journal of Fish Biology, researchers determined that a 1,323-pound female mako shark caught in 2013 had extremely high levels of DDT, PCBs, and mercury. "I wouldn't eat that," Kady Lyons, the study's lead author, told the Orange County Register. "It's definitely something you would not want to eat if you were planning on having children because it has reproductive consequences."
Analyzing the shark's liver, scientists found DDT levels 100 times the legal limit of consumption allowed by the EPA, and PCB levels 250 times the limit. The shark's flesh was determined to have mercury 45 times the legal limit for women and children to eat it.
Both DDT (the pesticide made prominent in Rachel Carson's Silent Spring) and PCBs (polychlorinated biphenyl, substances used in electronics manufacturing) were outlawed in the 1970s due to their toxicity, but the chemicals have persisted in the waters. Locally, the DDT in the waters primarily came from the Montrose Chemical Corporation DDT manufacturing plant in Torrance, which has since been shut down. Because of the accumulation of the chemicals in the seabed, the seafloor off the Palos Verdes Peninsula has been declared a Superfund site. An estimated 14 tons of DDT is thought to be down there, and animals found throughout the waters have been observed with the DDT in their flesh.
Sharks and other large fishes often have higher levels of toxins in their meat due to a process known as bioaccumulation, and officials have advised against eating several species of fish caught off our waters.
Aside from absorbing the toxins through the food they eat, female sharks also pass the substances off to their offspring, further adding to their persistence in the ecosystem. However, the local sharks have yet to show any ill effects from the chemicals. "Maybe these animals have developed ways of dealing with these contaminants that other vertebrates haven't," said CSULB professor Chris Lowe, another co-author on the paper.
The mako shark was caught for a reality TV show in 2013 off Huntington Beach and, at the time, was thought to be the world record for largest mako ever caught. It was donated to the scientists, who also cut open its stomach and discovered its last meal: a 4-year old sea lion.
