Recently published reports of research carried out in Belize indicate that marine protected areas are good for shark populations, both because the sharks themselves are safe from fishing and because the lack of fishing means sharks have more food to eat:
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.”
Edward Brooks, program manager for the shark research and conservation program at the Cape Eleuthera Institute, called it “a pretty novel study” for its non-invasive method. Normally, scientists track sharks by catching them on a line and inserting either a radio or satellite tag to monitor them.
Brooks, who reviewed the paper and has deployed chum cams in the Atlantic, noted that although many governments are exploring ways to reduce fishing pressure on sharks, “it doesn’t work if there isn’t any fish for the sharks to eat. Creating a marine reserve is a much more effective way to undertake conservation measures than to just stop fishing sharks.”
You can also read the complete original journal article Reef Sharks Exhibit Site-Fidelity and Higher Relative Abundance in Marine Reserves on the Mesoamerican Barrier Reef, which was published last week in open-access journal PLoS ONE.
[Image: via sciencecodex.com]