The full title of this blog post by Mickey Charteris is “Caribbean shark populations declining: Why it is happening and why we should care.” Charteris is an author/photographer living on Roatan. His book Caribbean Reef Life first came out in 2012 and is now into its fifth printing (as an expanded third edition). Read the full article at Caribbean Reef Life blog. The article explains various reasons for declining numbers of sharks, such as overfishing, longline fishing, and shark finning, among others. Charteris also offers other links to articles and videos, such as a very good article by Oceana.org on the importance of sharks for healthy reefs, and a video from the PEW Charitable Trusts.
For many divers in the Caribbean spending time with a shark underwater, however briefly, is the pinnacle of a diving day or even a diving trip, but this is becoming all too rare. These beautiful animals are being driven to extinction by modern fishing practices. Over the years, I’d snapped a few grainy pictures of hammerheads off in the distance and I was happy to get them, but the first time I was lucky enough to get in close for a proper shot of a Scalloped Hammerhead, it had a large steel hook with a wire leader trailing from its mouth!
Last month while diving on my favorite site we came across this dead Nurse Shark that had been sliced open, obviously by a fisherman’s knife. It must have just happened as blood was still flowing out of the wound, it’s a popular site for fishermen going after snapper and grouper. The hook had been removed, but why kill the animal? It highlights two reasons sharks are in danger, poor fishing practices and an unwarranted bad reputation for these important animals. It made me want to look deeper. Where are all the sharks?
A recent report by the Pew Charitable Trusts says that global shark populations have declined by as much as 70 to 80 percent, a brink they may well not be able to recover from. Like most apex predators, sharks reach sexual maturity very late in life (10-20 years) and may only produce one or two pups a year, so there is no hope of these stocks being replenished if things continue as they are. A conservative estimate is that 100 million sharks are being killed every year.
The Caribbean shark fishing industry boomed in the 1950’s with demand for their liver, skins and fins, and tripled during the 80’s. Caribbean shark and ray landings peaked in 1990, with more than 9 million metric tons that year. It was obviously unsustainable but has had far-reaching impacts on the Caribbean as a whole.
Sharks have been in the world’s oceans for over 400 million years and they play a crucial role in the health of Caribbean reef ecosystems. They are known as “keystone species” and their role is to keep other fish populations in check, so that the delicate balance of a coral reef is maintained. Dr. Stuart Sandin of the Scripps Institution of Oceanography has been studying why so many degraded reefs in the Caribbean are being taken over by algae. It is called an ecological cascade effect, where the removal of one key species changes the entire system. Once the sharks are removed from a reef other carnivore species such as groupers move in to fill the void. These groupers then overfeed on the herbivores such as the surgeonfishes and parrotfishes that are normally responsible for clearing the coral of algae.
And no, the fact that we are also putting species like the Nassau Grouper on the Critically Endangered Species List is not helping the situation. It’s all inter-connected down there. By removing the keystone species we are placing the whole reef, and even the livelihoods of people who depend on them, at risk. [. . .]