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Protecting Herbivorous FishesAlgae-Grazing Parrotfishes Provide Critical Role on Coral Reefs
Herbivorous fishes, like the queen parrotfish, need protection from overfishing in order that they can keep algae growth on degraded tropical reefs under control.
Herbivores provide a critical function in the marine environment. While snails take the lead in controlling marine algae in the intertidal zone and in the aquarium, it is herbivorous fishes that fulfill this role on tropical reefs. Herbivorous fishes are essential to tropical reefs because, once established, algae prevent new coral from competing for space on reefs, converting coral-dominated habitats to algae-dominated habitats. In short, maintaining healthy populations of herbivorous fishes on the world’s reefs is critical to reef conservation. Maintaining Coral-Dominated HabitatsAs tropical reefs continue to suffer secondary to global climate change, coastal development and a variety of other factors, marine scientists are seeing fewer coral-dominated habitats in both the tropical Atlantic and the Indo-Pacific. As a result, many researchers have turned their attention to studying fishes that eat algae, and now conservationists are also looking at those same species. Importance of Grazing FishesParrotfishes and surgeonfishes have received the most attention as the important herbivores on tropical reefs. While there are other groups of fishes that may play a critical role in reversing macroalgae growth once it has already been established, it is largely up to the parrotfishes and the surgeonfishes to keep the algae growth under control in the first place. Tropical western Atlantic reefs have been severely degraded over the past thirty years as a result of diseases (such as the one that nearly wiped out all herbivorous urchins in the mid-1980s), coral bleaching events and the effects of terrestrial runoff. There is now a concern that these degraded reefs face an even greater threat—the overfishing of herbivorous fishes. Conserving Ecosystem SustainabilityNew research has shown that it is essential to establish sustainable fish removal practices, where the only criterion for protection is not that species’ local extinction. Instead, sustainability must be defined from an ecosystem standpoint, but first, scientists must learn how many herbivores it takes to maintain a healthy coral-dominated ecosystem. It’s then up to regulators to insure that a surplus of herbivorous fishes remains on the reef after all fishing activities. The Unprotected Queen ParrotfishMany scientists involved in this research advocate a combination of marine reserves and fisheries legislation as many important species still have little if any protection. In the Caribbean, for example, marine scientists believe the queen parrotfish (Scarus vetula) is one of the most important herbivorous fishes, yet the species is not considered at risk based on species survivability. At present, the queen parrotfish is unregulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and is not listed with either the United States Fish and Wildlife Service or the International Union for Conservation of Nature. “[The queen parrotfish] is probably the most important herbivore on many Caribbean reefs,” says Dr. Peter Mumby, professor of coral reef ecology at the University of Exeter in the United Kingdom. Mumby’s research is focused on the resilience of coral reefs, with an emphasis on studying the role of algae grazing parrotfishes, and he believes the species is a good candidate for protection through regulation. The Resilience of Coral Reefs Depends on Herbivorous FishesMumby’s research, which was published in the journal Nature (“Thresholds and the resilience of Caribbean coral reefs”) in November 2007, was the first research to provide concrete evidence that herbivorous fishes are essential to the health of coral and, in turn, the tropical reefs built by coral. “Coral reefs are unique ecosystems that have supported thousands of fish and other marine species for millions of years,” says Mumby. “We estimate that humans have already destroyed around 30% of the world's coral reefs, and climate change is now causing further damage to coral. These findings illustrate the need to maintain high levels of parrotfishes on reefs in order to give corals a fighting chance of recovering.” Additional Resources:
The copyright of the article Protecting Herbivorous Fishes in Environmentalism is owned by Ret Talbot. Permission to republish Protecting Herbivorous Fishes in print or online must be granted by the author in writing.
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