Parrot fish critical to Coral Reefs sustainability Scientists Warn

Coral reefs could be damaged beyond repair, unless we change the way we manage the marine environment। New research by the Universities of Exeter and California Davis, published November 1, 2007 in Nature, shows how damaged Caribbean reefs will continue to decline over the next 50 years.

Coral reefs conjure up images of rich, colourful ecosystems yet an increasing number of reefs are becoming unhealthy and overrun by seaweed. The research team wanted to test whether reefs that are overgrown with algae could return to good health if the original causes of the problem, such as fishing or pollution, were addressed. This could mean, for example, reducing fishing or introducing better sewage management. The study revealed that the answer is ‘no’ because coral reefs can become permanently unhealthy.
In the 1980s, reefs in the Caribbean were hit by the devastating impact of the near-extinction of the herbivorous urchin, Diadema antillarum, with devastating results. Along with parrotfish, this grazing urchin kept seaweed levels down, creating space for coral to grow. Parrotfish are now the sole grazers of seaweed on many Caribbean reefs, but fishing has limited their numbers. With insufficient parrotfish grazing, corals are unable to recover after major disturbances like hurricanes and become much less healthy as a result. The team discovered this result by creating and testing a computer model that simulates the effects of many factors on the health of Caribbean reefs.
Professor Peter Mumby of the University of Exeter, lead author on the paper said: “The future of some Caribbean reefs is in the balance and if we carry on the way we are then reefs will change forever. This will be devastating for the Caribbean’s rich marine environment, which is home to a huge range of species as well as being central to the livelihood of millions of people.”
The paper argues that in order to secure a future for coral reefs, particularly in light of the predicted impact of climate change, parrotfish need to be protected. Parrotfish are frequently caught in fish traps that are widely used in the Caribbean, with many ending up on restaurant diners’ plates.
Professor Peter Mumby continued: “The good news is that we can take practical steps to protect parrotfish and help reef regeneration. We recommend a change in policy to establish controls over the use of fish traps, which parrotfish are particularly vulnerable to. We also call on anyone who visits the Caribbean and sees parrotfish on a restaurant menu to voice their concern to the management.”
This research was funded by the US Environmental Protection Agency, the Royal Society, the Natural Environment Research Council and the National Science Foundation.
This research was published in Nature: vol 450, issue 7166.
Adapted from materials provided by University Of Exeter.

Parrotfish on Menu Puts Caribbean Coral at Risk

LONDON - The delicate balance of the Caribbean's coral reefs is in jeopardy as more parrotfish end up on dinner plates, international scientists said on Wednesday.
The colourful grazing fish, named for their parrot-like beaks which are used to scrape up algae, play a vital role in stopping seaweed from smothering coral. But their numbers are now being threatened by over-fishing.
New research based on computer modelling shows parrotfish are a key defence in preventing the vulnerable Caribbean reefs from becoming a very different ecosystem -- one dominated not by living coral but by blooms of algae or seaweed.
"The future of some Caribbean reefs is in the balance and if we carry on the way we are then reefs will change forever," said Peter Mumby, a marine biologist from Exeter University, England, who led the research.
"Things have a habit of spiralling out of control and if a reef is allowed to get into an unhealthy state, covered in seaweed, it is extremely difficult to turn that around," Mumby added.
Coral reefs around the world are under threat from climate change, due to warming seas and increased ocean acidity, but the problem is particularly acute in the Caribbean following a series of disasters in the 1980s and 1990s.
The most devastating was the near-extinction of the long-spined sea urchin in 1983, due to disease. These grazing urchins had kept down seaweed levels and their disappearance leaves parrotfish as the sole grazers on many Caribbean reefs.
Compounding the problem, a number of hurricanes, starting with Hurricane Allen in 1980, have destroyed coral colonies and given invading seaweed new space to take hold.
The result, according to projections published in the journal Nature by Mumby and colleagues at the University of California, Davis, is that coral reefs could be damaged beyond repair unless management of the marine environment is changed urgently.
Top of the list should be controls over the use of fish traps -- devices similar to lobster pots that are used to catch most parrotfish.
Although not renowned for their flavour, parrotfish have become increasingly popular in restaurants around the Caribbean following over-exploitation of more prized fish species such as grouper and snapper.
"We need to think about parrotfish in the entire coastal zone. It is not enough to say we'll protect parrotfish in marine reserves and we'll fish them outside. We have to try and control the fishing everywhere," Mumby said in a telephone interview.
There are currently very few restrictions on fishing for parrotfish outside protected Caribbean marine parks, although catches are rare in Florida and Bermuda, where fish traps are not used.
Story by Ben Hirschler
Story Date: 1/11/2007