Sharks! The very word strikes fear in some swimmers, surfers and beachgoers.  But those top predators play an important role in reef ecosystems.

Now research shows there is a drastic drop in the numbers of reef sharks around populated islands -- including Hawaii.

While the occasional aggressive large shark, like a tiger or even a great white gets most of the attention, other smaller reef sharks are also found in our waters. But researchers discovered those reefs sharks are getting harder to find, when compared to pristine reefs around the Pacific.

"We found 90-97 percent decline in reef shark abundance, white tip, grey, galapagos and nurse sharks," said Marc Nadon, a researcher with the Joint Institute for Marine and Atmospheric Research.

Without those top predators, it is believed the entire reef food chain can be disrupted. A lack of sharks could also have an impact on coral reefs themselves.

While researchers were able to easily spot the absence of sharks in our waters, they have not been able to determine the reason behind those lower numbers.

"We can't pinpoint why there is a such a decline, we think it may be a mix of fishing pressure," said Nadon.

Many times sharks are inadvertently caught by island fishermen.

"I'm actually very surprised because that's all I catch, is sharks, pufferfish and anything else I don't want"

Researchers have not only seen a drastic drop in shark populations in Hawaii and other populated islands around the Pacific, they have seen a 75 percent reduction in reef fish as compared to pristine waters.