Monitoring in Kahekili Herbivore Fisheries Management Area Indicates an Increase in Fish Biomass and Improved Conditions for Corals

Five years after the Kahekili Herbivore Fisheries Management Area was established in West Maui, in the main Hawaiian Islands, monitoring indicates an increase of herbivorous fish biomass there and early signs of improved conditions for corals.

The Kahekili Herbivore Fishery Management Area (KHFMA) in Kaʻanapali, West Maui, was established by the state of Hawaii in July 2009. It involves a form of management unique within the state, namely protection of coral reef herbivores (i.e., surgeonfishes, parrotfishes, chubs, and sea urchins), which may not be killed, injured, or harvested within the boundaries of this fisheries management area. The goal of the KHFMA is to restore natural grazing processes and thereby increase the local reef's ability to resist and recover from excessive algal growth that had occurred repeatedly on local reefs through the 1990s and early part of the 2000s.

Since 2009, the PIFSC Coral Reef Ecosystem Division (CRED) has partnered with the Division of Aquatic Resources (DAR) of the Hawaii Department of Land and Natural Resources to conduct twice-annual surveys of fishes and benthos within the KHFMA.

Algal bloom at Kahekili in 2001. Algal bloom at Kahekili in 2005.
Algal blooms occurred at Kahekili in 2001 (left) and 2005 (right).

Thus far, the KHFMA has restricted harvesting of reef herbivores for 5 years, a period that is considerably shorter than the lifespan of many of the herbivorous fish species that are protected inside the KHFMA. Therefore, full effects of protection on those fish species and on slow-growing corals will not be clear for several more years. Here are some highlights from the survey results to date (the most recent surveys were March 31–April 3, 2014):

CRED staff and DAR partners planned to conduct the next round of monitoring in late September 2014.

Semi-annual surveys indicate that mean biomass densities of surgeonfishes at the Kahekili Herbivore Fishery 
        Management Area have increased since the conservation area was created. Error bar shows 1 standard error of the mean. Semi-annual surveys indicate that mean biomass densities of parrotfishes at the Kahekili Herbivore Fishery 
        Management Area have increased since the conservation area was created. Error bar shows 1 standard error of the mean.
Semi-annual surveys indicate that mean biomass densities of surgeonfishes and parrotfishes at the Kahekili Herbivore Fishery Management Area have increased since the conservation area was created. Error bar shows 1 standard error of the mean.