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updated: 11/12/2013 12:11 AM

Harm to the oceans can make sharks sick

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  • Sharks in the Shedd Aquarium Wild Reef exhibit. Sharks can get sick just like any other animal, but humans can help them by not polluting the oceans.

    Sharks in the Shedd Aquarium Wild Reef exhibit. Sharks can get sick just like any other animal, but humans can help them by not polluting the oceans.
    Courtesy of Shedd Aquarium/Brenna Hernandez


Editor's note: Two name spellings were corrected after this article first appeared online.

You wanted to know

Students in Nancy Sullivan's sixth-grade class at Frederick Nerge Elementary School in Roselle asked, "Do sharks get sick? How? Why?"

Sharks rule the oceans as the top predator. They play a key role, and are called a keystone species because they keep marine populations in check by weeding out the sick and the old. When sharks prey on the weakest ocean species, they stop the spread of disease and help improve the gene pool.

When it comes to health issues, sharks aren't so different from any other animal, or even people.

Lise Watson, Chicago's Shedd Aquarium Wild Reef collections manager, said, "Just like other animals, they are susceptible to a variety of different diseases, including bacterial, viral and fungal infections and can also suffer from parasitic infestations. However, just like us, they have an immune system that helps their bodies to fight off these intruders that can make them sick."

Shark populations have diminished worldwide, with as many as 73 million being killed each year, according to the Monterey Bay Aquarium in California. If a keystone species is reduced or eliminated, the ecosystem can be changed forever.

Sharks can become ill when there are changes in their environment, according to Andrea Rodgers at the Shedd Aquarium.

"Oil spills are a good example of this," Rodgers said. "Also, significant changes in water temperature can cause sharks to become ill or even die."

Research conducted by the Monterey Bay Aquarium tracks traces of the toxins PCB and DDT in mother sharks, chemicals that have been banned for decades but linger in ocean waters. Scientists are trying to determine if these chemicals cross over to baby sharks.

Dr. Mike Murray, Monterey Bay Aquarium veterinarian, said poor food quality can make sharks in the wild sick.

"Bad food, not enough food, and the wrong types of food can also make animals, including people and sharks, sick," Murray said.

"So, some of the harm that is being done to the oceans and the animals that live in them can affect sharks by affecting their food. There are lots of things that make sharks sick, but we can do an awful lot to protect them and keep them healthy by making sure that their oceans are kept healthy."

Anyone can help keep sharks and other marine animals healthy by taking care of how they dispose of chemicals, medicines and other pollutants.

"Among the things we can do to help keep sharks from getting sick is to limit the chemicals we use, and the flow of those chemicals into rivers, lakes and oceans where wildlife lives," said Monterey Bay Aquarium's Ken Peterson.

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