Researchers examined data from 48 different studies of 318 reefs across the Caribbean from 1955 to 2007.

They found that fish density grew from 1955 to 1985, when it began to decline slightly. The significant losses began in 1995, when density fell across the region by 2.7 to six percent per year.

"We were most surprised to discover that this decrease is evident for both large-bodied species targeted by fisheries as well as small-bodied species that are not fished," said lead author Michelle Paddack of Simon Fraser University in Canada.

"This suggests that overfishing is probably not the only cause."

Paddack and her colleagues point to an 80 percent reduction in coral cover since the mid 1970's and drastic changes in coral reef habitats over the past 30 years as the most likely culprit.

These changes are a result of a number of factors, including a rise in pollution from coastal development, warming ocean temperatures, coral diseases, and overfishing which led to the decline of many fish species important to keeping the reefs free of algae.

"All of these factors are stressing the reefs and making them less able to recover from disturbances such as hurricanes, which also seem to be occurring more frequently," Paddack said.

The delayed response to loss of coral implies a "degradation debt."

Paddack said her study, which involved a very large team of scientists from around the globe, should serve as a call to action.

"If we want to have coral reefs in our future, we must ensure that we reduce damage to these ecosystems," she said.

"On a personal level, this may mean not buying wild-caught aquarium fish and corals, not eating reef fish species that are declining, taking care not to anchor on reefs, and reducing our carbon emissions to help control climate change.

"But importantly, we need to let lawmakers and resource managers know that we care about these ecosystems and we need to push for changes in how they are managed."

The study was published in the peer-reviewed journal Current Biology.

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