Herbivorous reef fishes critical for long-term coral reef health and resilience

Herbivorous reef fishes not only have a key role in keeping algal growth at bay and thereby enabling corals to grow and reproduce, they are also important players in the long-term health and survival of coral reefs in the face of climate change and other threats. These are the findings of a new report published by IUCN and its institutional partners released today.

The report, which focuses on the Asia-Pacific region, takes an in-depth look at the interaction between coral communities, algae and herbivorous reef fishes. It goes on to offer practical advice to coral managers on how to monitor the abundance, biomass and size structure of these important species.

In the perpetual battle for supremacy between coral and algae, herbivorous fishes are the linchpin working in favour of corals by limiting the establishment and growth of algal communities that impede coral recruitment. Each functional group studied by the report - including grazers, browsers, scrapers and excavators - play different but complementary roles in maintaining the resilience of coral reefs.

"Coral reef monitoring has traditionally focused on monitoring the status of coral communities and populations of conspicuous species, particularly fisheries species like fish and invertebrates." says report co-author Alison Green of The Nature Conservancy. "This provides useful information on the current status of coral reef communities and associated fisheries, but does not provide information on the status of key ecological processes that are essential for maintaining coral reef resilience."

Developing new metrics for monitoring coral reef resilience that are process oriented is an urgent priority for the improved management of coral reefs. This report presents a protocol for monitoring functional groups of herbivorous reef fishes, which play a critical role in coral reef resilience.

Under threat

With close to 500 million people in the world living within 100km of coral reefs - many of them living subsistence lifestyles - fishing pressure on herbivorous fishes can be intense. Overfishing of some of the larger species of herbivorous fish has led to worrying declines and, some species, for example humphead parrotfish, are now only common in remote areas or areas where fishing is prohibited.

"The good news is that herbivorous fishes can bounce back if given adequate protection." says David Obura, Chair of the IUCN Climate Change and Coral Reefs Marine Working Group. "Populations of herbivorous fishes tend to recover quickly after protection in no-take Marine Protected Areas. Evidence also suggests that coral reefs with low fishing pressure and relatively intact food webs provide greater resilience to threats such as climate change."

Deadly frog fungus targeted by amphibian experts

The world’s leading amphibian experts have come together and for the first time identified two major conservation initiatives to stop amphibians going extinct.

A new coalition of organizations, the Amphibian Survival Alliance, will be set up to focus on containing the spread of the amphibian chytrid fungus and protecting habitats which are home to amphibians that occur nowhere else in the world.

Amphibians are the most threatened group of animals in the world, with one in three of the 6,000 recognized amphibian species at risk of extinction.

“The world’s amphibians are facing an uphill battle for survival,” says James Collins, Co-Chair of the IUCN Amphibian Specialist Group. “Infectious diseases, habitat loss, climate change, introduced species, commercial use and pollution all affect amphibian survival. By far the worst threats are infectious disease and habitat destruction so the Alliance will focus on these issues first.”

The alliance, proposed at the first Amphibian Mini Summit, at the Zoological Society of London last week, brings together amphibian specialists working in the wild and those in zoos, aquariums and botanical gardens.

“If we want to stop the amphibian extinction crisis, we have to protect the areas where amphibians are threatened by habitat destruction,” says Claude Gascon, Co-Chair of the IUCN Amphibian Specialist Group. “One of the reasons amphibians are in such dire straits is because many species are only found in single sites and are therefore much more susceptible to habitat loss.”

Curbing the spread of amphibian chytrid fungus is also a top priority for the amphibian experts. This effort will focus on identifying the presence of naturally-occurring bacteria, which seem to render some amphibians resistant to the killer frog disease, and investigating their use in managing the disease in other species. So far these bacteria have only been found on a few species and this approach needs more research.

Anti-fungal drugs to combat the deadly disease, exploring resistance in captive-bred populations and translocations all need to be investigated. The alliance will look into policies to prevent the spread of the fungus to new places, such as Madagascar, which so far shows no evidence of the presence of the amphibian chytrid fungus.

“Amphibians have so much to offer humans,” says Simon Stuart, Chair of the IUCN Species Survival Commission and convenor of the Amphibian Mini-Summit. “Many have an arsenal of compounds stored in their skin that have the potential to address a multitude of human diseases. However, opportunities are being lost, such as the Southern Gastric Brooding Frog, which could have led to the development of a medicine for human peptic ulcers, had it not gone extinct. We simply cannot afford to let this current amphibian extinction crisis go unchecked.”

The new Alliance will work with partners to implement the Amphibian Conservation Action Plan and to raise the profile of amphibians in 2010, the International Year of Biodiversity.