Protecting Herbivores
Herbivores, are essential for supporting reef resilience and preventing macroalgae from over-growing corals. Coral reef managers can play a key role in herbivore protection by regulating herbivore removal in MPAs and by working with fishers and fishery managers to protect the viability of herbivore populations in the wider reef ecosystem. Fisheries legislation provides legal frameworks for protecting herbivores, but most existing fishery management strategies have not been designed to protect functional roles such as herbivory.
A range of conventional fisheries management tools and strategies are available for protecting herbivores. These include:
Protected Areas
Prohibiting removal of herbivores (or general bans on fishing) in portions of habitat or at sites important for herbivores (such as aggregation sites) can help maintain herbivore populations.
Gear restrictions
Herbivores generally are not caught in hook and line fisheries, and instead are targeted using traps, nets, or spears. Some herbivorous fishes, such as parrotfishes, are especially vulnerable to nocturnal spearfishing and spearfishing on SCUBA. Limiting use of certain types of fishing gear or fishing times can reduce pressure on herbivores.
Species bans
The most effective way to protect herbivores is to place a total ban on collection of key herbivore species. This has now been implemented in several locations, including Belize. Market-based approaches, such as prohibiting the sale of herbivores, can prevent commercial fishing for herbivorous species although subsistence fisheries can still be a significant source of pressure in many locations.
Temporary closures
The role of herbivores can be especially important after disturbance events that kill corals, such as hurricanes or mass coral bleaching. Managers can consider a temporary restriction on harvesting important herbivore species to maximize the chance that coral populations will be able to recover without the added pressure of excessive competition with algae.
Herbivore restoration
In cases where herbivore populations have been reduced through overfishing or disease, active restoration may be the most feasible way to rebuild populations to the level required to prevent or reverse a phase shift. Depleted urchin populations have been the focus of assisted recovery trials in some places where they are one of the main sources of herbivory (which may be symptomatic of depleted fish herbivore populations), but there have not yet been any examples of successful broad-scale restoration.
Parrotfish control algal growth and maintain the reef substrate for coral recruitment. Photo © Jeff Yonover
To control the overabundance of marine algae on coral reefs in Maui, Hawai‘i, the Kahekili Herbivore Fisheries Management Area was established. It was designed to increase the local abundance of certain herbivorous fishes and sea urchins through fisheries management methods. For example, hatchery-raised juvenile urchins (Tripneustes gratilla) have been released onto the reef to graze the invasive algae and promote recovery of the reef.
Video: Using Herbivores to Save a Reef (2:39)
Darla White, State of Hawaii Division of Aquatic Resources, describes how fisheries are managed for reef resilience.
Natural controls of marine algae are intended to help the marine ecosystem in the area return to a healthy balance. The management area prohibits the fishing of any fish in the following families: Kyposidae (sea chubs), Scaridae (parrotfishes) or Acanthuridae (surgeonfishes) or any sea urchins.