Batfish May Come To Great Barrier Reef's Rescue

[mrmoshe]

Batfish may come to Great Barrier Reef's rescue

A rare fish could be the surprising key to allowing coral reefs to recover from overfishing, say scientists at James Cook University in Queensland, Australia.

The group simulated the overfishing that affects large areas of the Great Barrier Reef by placing cubic cages – 5 metres to a side – on the reef to prevent any fish over 3.5 centimetres wide from getting in. In the absence of the larger fish, swathes of choking seaweed overtook the reefs.

Three years later, they removed the cages and filmed the reef's recovery. They expected well-known herbivorous fish, such as parrotfish and surgeonfish, to eat up the seaweed.

Neither species was able to make a dent in the damaging algae. Nor did any of the remaining 41 herbivorous fish found in the area make much of a difference. Instead, the researchers found that a rare batfish, Platax pinnatus, moved in. The team was surprised to see the batfish act this way, as they usually feed on plankton and invertebrates on the sea bed.

“In five days the batfish had halved the amount of weed. In eight weeks it was completely gone and the coral was free to grow unhindered,” says David Bellwood, who led the study.

Profound implications

Another surprise was that the team's cameras regularly saw up to three of the fish feeding in one location. Usually, only one batfish is found in every 0.6 hectares, on average. The researchers say the batfish appear to have been attracted to the experimental plots by the plentiful seaweed.

The findings have significant implications for coral reef management efforts, the scientists believe. In particular, "a rich herbivore biodiversity may not offer the protection that one might assume", they write in Current Biology.While the usual herbivorous suspects may help maintain the reef and prevent it from becoming overgrown by large algae in the first place, they are not able to reverse that transition.

Functional groups

The researchers also point out that censuses that correlate the relative health of a coral reef with the presence of various fish species are likely to ignore ‘‘sleeping functional groups’’ that can play a vital role in the life of the reef, albeit only under exceptional conditions.

"Monitoring programmes would therefore fail to detect changes or declines in this critical functional group," say the researchers.

Batfish are vulnerable because of their large size, which makes them attractive to fishers, and because their young depend on coastal mangroves which are in decline in many areas.

For now, they are one of the last populations apparently capable of reversing the fate of coral reefs that have been damaged by overfishing. Already, the reef has all but lost two major weed-mowers: dugongs and green turtles.

“If Platax is the last grazer of dense weedy stands on inshore coral reefs and it goes into decline, the capacity of these reefs to recover from [changes] could be lost,” Bellwood warns.

Edited December 18, 2006 by MallacootaPete

[mrmoshe]

I wonder if the buggers like eating Caulerpa Weed?

If so, I wish someone would bring a truckload of 'em down to Pittwater to chow down.

Pete.