Managing Fisheries for Reef Resilience: Kahekili Herbivore Fisheries Management Area

 

Location

North Kāʻanapali, West Maui, Hawai‘i

The challenge

Long term monitoring of coral reefs along the leeward coast of the Island of Maui began in 1999 by the State of Hawai‘i’s Division of Aquatic Resources (DAR) and the University of Hawai‘i’s (UH) Institute of Marine Biology’s Coral Reef Monitoring Assessment Program. Many of these coral reef survey locations were established at previous study sites, providing managers with a longer-term picture of the changes on these reef systems. Assessments have shown that of the ten reefs monitored, many sites experienced a significant decrease in live coral cover as reefs became overrun by invasive algae. At Kahekili in north Kāʻanapali, Coral Reef Assessment and Monitoring Program (CRAMP) sites demonstrated a decrease in coral cover from 55% to 33% between 1994 and 2006. In 2009, when Kahekili Herbivore Fisheries Management Area (KHFMA) rules went into effect, coral cover was 37% at CRAMP study sites and in the broader KHFMA. In 2020, the average coral cover at CRAMP sites was about 27%, a decrease from broader 2018 NOAA survey results which indicated coral cover was around 31% in the KHFMA and 33% on CRAMP sites.

The significant increases of invasive algae were seen as a major threat to West Maui’s coral reefs. At Kāʻanapali, specifically, red algal blooms of Acanthophora spicifera had become much more abundant, which was suggested by UH research to be a result of elevated nutrients from wastewater and fertilizers. In addition to the sources of land-based pollution, the increasing abundance of algae was exacerbated by the fact that there was a decrease in abundance of reef grazing herbivores, which fish surveys at the same sites confirmed.

Boundaries of the KHFMA along the Kāʻanapali Coast, West Maui. © Hawai‘i DLNR

Boundaries of the KHFMA along the
Kāʻanapali Coast, West Maui. © Hawai‘i DLNR

Actions taken

A cooperative “Fish Habitat Utilization Study” by DAR and the National Oceanic and Atmospheric Administration (NOAA) revealed clear evidence of the relationship between grazing fish and the abundance of invasive algae; the more herbivorous fishes present, the less algae there is on the reefs.

Therefore, in July 2009, the State of Hawai‘i designated the Kahekili Herbivore Fisheries Management Area (KHFMA) in order to control the overabundance of marine algae on coral reefs and restore the marine ecosystem back to a healthy balance. The killing, injuring, or harming of sea urchins and certain herbivorous fishes, including sea chubs, parrotfish, and surgeonfish is prohibited to increase the local abundance of these beneficial fishes and sea urchins in the area. Feeding of these fishes is also prohibited to promote grazing. The onshore boundaries extend from Honokōwai Beach Park (and offshore for a distance of 1,292 yards) south approximately 2 miles to Hanaka’ō’ō Beach (and offshore for a distance of 335 yards) (Hawai‘i Revised Statues, Chapter 13-60.7).

How successful has it been?

Although some were opposed to the fishing rules, the majority of the community was in strong support of the KHFMA. Many local fishers understood the poor conditions of the reef and realized the benefits of fisheries management. Local support for the KHFMA has led to more education within the area as well as compliance with the rules. However, there have been signs of increased poaching, especially during the COVID-19 pandemic. Fish data shows that large-bodied parrotfish and surgeonfish abundance is decreasing while small-bodied parrotfish and surgeonfish appear to be less affected.

Since the establishment of the KHFMA in 2009, DAR, in partnership with UH and NOAA’s Pacific Islands Fisheries Science Center (PIFSC), has continued monitoring the reefs at Kahekili. Monitoring results from 2018 and interim results of 2021 surveys are as follows:

  • 2018 results showed an increase in parrotfish biomass to more than four times its earlier level since the KFHMA was created. Interim results from 2021 indicate that parrotfish biomass declined to be consistent with 2015 levels (around 7 g/m2, roughly a 200% increase from 2009 levels).
  • 2018 surveys showed reduced cover of macroalgae and dense turf seaweeds, and a four-fold increase in crustose coralline algae (CCA). Coral cover appeared to be increasing through 2014, but a major bleaching event hit Maui in 2015 and resulted in a roughly 20% decline in coral cover. Surveys in 2021 show a sharp decline in CCA which coincides with the decline in parrotfish biomass, therefore indicating a strong correlation between parrotfish biomass and CCA (CCA increases with parrotfish biomass and decreases as parrotfish biomass drops).
  • Not all areas of the KHFMA recovered equally; there has been little to no recovery of parrotfish biomass observed in the nearshore shallow reef. Offshore reefs, spur and grove reefs outside of Honokowai point remain the areas with the highest biomass of parrotfish. However, deeper reef surgeonfish biomass levels have dropped to be more in line with nearshore beach park levels. Additionally, declines in numbers of some large-bodied and desirable fishery species since 2014 indicate that a low level of poaching is occurring and likely preventing full recovery of fish species across the KHFMA.
  • 2018 surveys showed a 71% increase in surgeonfish which was statistically significant at the time. However, 2021 surveys show a decline of surgeonfish biomass to levels equal to or lower than baseline levels in 2009 when the protection rules went into effect.

The steady increase in biomass of parrotfishes since the establishment of the FMA has potentially significant indications for reef resilience. The larger the fish, the deeper the excavating bites, which is important because this removes algae from the substrate, exposes bare rock and opens up new sites for coral recruitment. See the related case study on the long-term monitoring program in the Kahekili Herbivore Fisheries Management Area for more details.

Beneficial herbivorous fishes now fully protected within the KHFMA © Hawai‘i DLNR

Beneficial herbivorous fishes now fully protected within the KHFMA. © Hawai‘i DLNR

Lessons learned and recommendations

  • In addition to increasing stocks of herbivorous fishes on the reefs to control invasive algae, management must also include reducing sources of land-based pollution that is resulting in high levels of nutrients (nitrogen and phosphorus) found in nearshore waters, which is likely driving the algal blooms. Meaningful changes to land-based source pollution are difficult and take time. A 2021 Supreme Court decision ruled that wastewater injection wells fall under the Clean Water Act and therefore Maui County must have permits “if the addition of the pollutants through groundwater is the functional equivalent of a direct discharge from the point source into navigable waters.” Therefore, reductions in wastewater pollution through Maui County’s compliance with the Clean Water Act, improved treatment technologies, and increasing public awareness of the problem are expected.
  • Successful compliance with closures and protected area regulations requires continued education, outreach, and enforcement efforts.
  • Poor habitat quality resulting from invasive algae and subsequent degradation of reefs will also have lower economic (commercial and recreational) and cultural value.
  • Studies have shown that reef deterioration in the monitored sites occurred rapidly; therefore, resource managers must take steps to not only restore reefs back to their healthy conditions, but also prevent any further threats from degrading Maui’s reefs.
  • Public awareness about coral reef health and the negative impacts of land-based pollution on reef ecosystems has increased since the designation of the KFHMA. With the community’s support, West Maui reefs have since been designated as a priority site under the Hawai‘i Coral Reef Strategy, have been chosen for a Ridge to Reef cooperative watershed management project by the state and the U.S. Army Corps of Engineers, and have been designated as a priority site in the Pacific by the U.S. Coral Reef Task Force.
  • Reef recovery takes time – although data indicates an increase in biomass of parrotfishes, slow-growing corals will need long-term protection to fully recover. Additionally, while fish stock and coral recovery take time, just a few poaching events can completely erase any progress gained from protection and closure efforts.
  • Making a genuine effort to provide data and have a dialogue with the local community at the beginning of the planning process is essential to the success of the project. Community members will have greater trust, offer input, and be part of the problem-solving process.
  • Data that are specific, real time, and applicable are vital to having a supportive, knowledgeable community.
  • Identifying and engaging key stakeholders and fishers from the area can provide a wealth of local knowledge, as well as buy-in and compliance later on.

Funding summary

The process to establish the KHFMA was funded and staffed by the State of Hawai‘i’s Department of Land and Natural Resources (DLNR) as part of the agency’s mission and core responsibilities. Monitoring efforts have been funded primarily through a Sports Fish Restoration Program grant administered by the U.S. Fish and Wildlife Service. The islands of Maui and O‘ahu receive roughly US $300,000/year from the program, of which Maui spends about US $200,000 for monitoring staff and other associated costs. Other funding partners include:

NOAA Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center
NOAA Coral Reef Conservation Program (3-5 year funding cycles)
University of Hawai‘i
Graduate students with funding

Lead organizations

opens in a new windowHawai‘i Division of Aquatic Resources, Department of Land and Natural Resources

Partners

opens in a new windowHawai‘i Coral Reef Initiative Research Program
opens in a new windowNOAA Coral Reef Conservation Program
opens in a new windowNOAA Pacific Islands Fisheries Science Center, Coral Reef Ecosystem Division
opens in a new windowThe Nature Conservancy
opens in a new windowHawai‘i Institute of Marine Biology
opens in a new windowUniversity of Hawai‘i at Manoa, Department of Botany

Resources

opens in a new windowHawaii Coral Reef Strategy, State of Hawaii opens PDF file

opens in a new windowResponses of Herbivorous Fishes and Benthos to 6 Years of Protection at the Kahekili Herbivore Fisheries Management Area, Maui

opens in a new windowKahekili Herbivore Fishery Management – Interim Monitoring Resultsopens PDF file

opens in a new windowKahekili Herbivore Fisheries Management Area Rules

opens in a new windowStatus and Trends of Maui’s Coral Reefs, Hawai‘i Division of Aquatic Resourcesopens PDF file

opens in a new windowKahekili Herbivore Fisheries Management Area, Herbivore Management in an Effort to Improve Coral Reef Resilienceopens PDF file

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