Our friends at Oceans4Ever are hosting the first ever Summer Sharktakular this week, along with shark blogger extraordinare, David Shiffman. David wrote this guest post for us about the threats facing sharks in the Gulf. Be sure to check out the rest of the Sharktakular this week! – Emily
Many threats facing sharks, such as bycatch and finning, are well known to conservationists. Less well known, but just as serious to some species, are the threats to sharks from the Deepwater Horizon oil spill in the Gulf of Mexico.
Sharks can come into direct contact with oil on the surface, which appears to be happening to whale sharks. These threatened animals, the largest fish in the sea, feed by filtering plankton out of the water. In other words, they swim with their mouths open near the surface, which is a surefire recipe to ingest floating oil.
The estuaries of the northern Gulf are important nurseries for a variety of smaller shark species. Newborn sharks use the shallow waters, safe from predators and full of food, as a safe place to grow up. Oil has reached many of these estuaries, with unknown (but undoubtedly bad) long-term effects on the species that use them. Entire year-classes of some populations may die as their nursery grounds become poisoned.
Oil can also affect sharks if it enters the food web, which it appears to be doing. As Dr. Neil Hammerschlag of the University of Miami recently said in a CNN interview, “There’s fishing areas closed in the Gulf of Mexico because they don’t want people eating that fish, but I don’t know if sharks got the memo”. Sharks are likely eating oil-contaminated prey.
We will likely never know the full extent of the oil spill’s impact on sharks, since a dead shark will simply sink to the bottom of the ocean. You can rest assured, however, that sharks are being affected and the effects aren’t good.
David Shiffman is a graduate student at the College of Charleston. He writes about sharks for the marine biology blog SouthernFriedScience.com. To learn more about sharks, follow him on Twitter @WhySharksMatter.