All sharks have multiple rows of teeth, and while they lose teeth on a regular basis, new teeth continue to grow in and replace those they lose.
Shark overfishing hurst coral reefs
Overfishing for sharks is having detrimental effects on coral reefs, finds a new study published in the journal PLOS One.
The research is based on long-term monitoring reefs off northwestern Australia. The authors, led by Jonathan Ruppert, formerly of the University of Toronto and now with York University, compared community structure between several atoll-like reefs. Some of the reefs were protected, while some were open to exploitation by Indonesian fishermen using traditional fishing techniques. Indonesian fishermen tend to target high value species like sharks.
The researchers found the overfishing of sharks can result in profound ecological changes.
"The reefs provided us with a unique opportunity to isolate the impact of over-fishing of sharks on reef resilience, and assess that impact in the broader context of climate change pressures threatening coral reefs," said Ruppert. "Shark fishing appears to have quite dramatic effects on coral reef ecosystems."
“Where shark numbers are reduced due to commercial fishing, there is also a decrease in the herbivorous fishes which play a key role in promoting reef health.”
"Our analysis suggests that where shark numbers are reduced, we see a fundamental change in the structure of food chains on reefs," said project lead and co-author Mark Meekan.“We saw increasing numbers of mid-level predators – such as snappers – and a reduction in the number of herbivores such as parrotfishes. The parrotfishes are very important to coral reef health because they eat the algae that would otherwise overwhelm young corals on reefs recovering from natural disturbances."
The protected Rowley Shoals (Imperieuse, Clerke and Mermaid Reefs) and fished Scott Reefs (Seringapatam, North Scott and South Scott Reefs) were study sites. Image courtesy of Google Earth.
The findings indicate that reefs depleted of sharks may be slower to recover from longer-term disturbances, including cyclones and bleaching events. Accordingly, the results suggest that protecting small reefs from shark fishing could make these ecosystems more resilient to the effects of climate change.
"Healthy populations of reef sharks should be a key target of management strategies that seek to ensure the future resilience of coral reef ecosystems," conclude the authors.
Read more at http://news.mongabay.com/2013/0920-shark-fishing-reefs.html#HRvmTPPUJYukCETd.99
Sharks are simply fascinating. For most divers, swimming with the sharks is a breathtaking experience, especially when you know some of the most interesting facts about what makes these creatures of the sea so special.
Check out these unique facts about sharks:
- Sharks have excellent dental health. Not only are their damaged teeth continuously replaced throughout their lifetime, they are covered in fluoride (fluoroapatite to be exact) making them resistant to decay.
- Did you know some sharks can glow? Lantern sharks camouflage themselves from predators by emitting a similar level of light as what is coming from the water’s surface so they avoid casting a shadow. One example is the dwarf lantern shark that is found off the coast of Venezuela and Columbia, which can fit in the palm of your hand.
- Shark mothers have a tough job. Not only must they have tough skin because they often are bitten during the mating process, the gestational period of their young can last anywhere from five months to two years, depending on the species.
- Whale sharks are the biggest shark species in the world. And big sharks like big families – one female can have up to 300 pups in just one litter.
- Living in warm, oceanic waters around the world, the cookiecutter shark is fairly small at 42 to 56 centimetres (17 to 22 inches), but is known to attack other much larger sharks. The name cookiecutter comes from the circular plug bites, reminiscent of an ice-cream scoop or cookie cutter, that it takes out of its victims.
- A shark’s jaw is incredibly strong. One single bite applies up to 40,000 pounds per square in or pressure. Furthermore, sharks are able to dislocate their upper jaw, unlike us humans. This comes in handy while hunting and killing prey.
Although movies and TV teach us to fear sharks, it reality they are the ones that should fear us. About 100 million sharks are killed each year by humans for numerous reasons, including for their fins, teeth, meat or vertebrae. To protect sharks from extinction and the delicate ecosystems they help balance, visit www.projectaware.org.
In honor of the Finathon event that I’m helping organize at the end of the week, I’m gonna be posting (more) informational posts about the ocean’s top predators! Shark Talk, all week long til December 15th; just sharks, nothing else. (Except maybe on the last day, when I decide to post stuff about the event because not only we’re making people swim non-stop, we’re making people swim non-stop with fins! I have a feeling it’s going to be a fintastic swimathon.)