Video: Filmed at Glover's Reef Marine Reserve, a coral atoll, a juvenile Nurse shark (Ginglymostoma cirratum) and Caribbean reef shark (Carcharhinus perezi) battle it out for access to a bait cage.

Using ‘chum cams,’ scientists find protected areas benefit sharks

For years, scientists and policymakers have debated whether putting parts of the sea off-limits to fishing actually benefits such wide-roving predators as sharks. Now, thanks to some dead sardines in front of an underwater camera, they have proof.

A team of scientists from the United States and Belize picked four ocean locations to survey over five years, from 2005 to 2010. In each spot they put a waterproof video camera on the seafloor in front of a small bait cage — contraptions they nicknamed “chum cams.” Then they counted how many sharks showed up on film.

The results — reef sharks are more common in areas where fishing is restricted — were published online Thursday in the journal PLoS ONE. The findings are significant because policymakers in the United States and overseas are now debating whether to create more protected areas known as marine reserves. Although scientists have proved in the past that many sedentary marine species benefit from putting certain parts of the ocean off-limits to fishing, there is less documentation that this benefits large, roving predators such as sharks.

Using both acoustic monitoring and chum cams, the team showed that Caribbean reef sharks in Belize showed up more often in Glover’s Reef and Caye Caulker Marine Reserves than in two other areas where fishing is not restricted.

Twenty-nine percent of chum cam deployments videotaped at least one reef shark in those reserves, compared with 8 percent of deployments on fished sites. Caye Caulker is entirely off-limits to fishing, while Glover’s Reef has a ban on longline and gill net fishing but allows other kinds of fishing in certain areas.

Mark Bond, a doctoral candidate at Stony Brook University and the paper’s lead author, said a combination of two factors accounts for why they found more sharks inside the protected areas: “the fact that there’s more of their food in the reserves, and the fact that there’s no fishing.”

Sharks find a fishy snack

Mar. 8, 2012 - Filmed at Caye Caulker Marine Reserve on the main barrier reef, a healthy school of yellowtail snapper show that the marine reserves also benefit a variety of fish species. Just off the bait cage are two adult reef sharks coming in inquisitively to seek the source of the chum. Adult sharks often exhibit a much more cautious approach to food sources, as is witnessed here. (Institute for Ocean Conservation Science at Stony Brook University)

Sharks and fish species under protection

Mar. 8, 2012 - At Glovers Reef Marine Reserve, a variety of grouper species and healthy corals as well as juvenile nurse and reef sharks attempt to get bait.