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Hopeful signs of reef recovery emerging in North Kaanapali

By Staff | Oct 12, 2017

The coral reef offshore of Kahekili Beach Park in the summer of 2006. At this time, nearly 40 percent of the substrate was covered by seaweed. PHOTO BY THE HAWAII DEPARTMENT OF LAND AND NATURAL RESOURCES, DIVISION OF AQUATIC RESOURCES.

KAANAPALI – In 2009, a novel form of fisheries management officially went into effect along an approximately two-mile section of the north Kaanapali coastline in West Maui.

This area – the Kahekili Herbivore Fisheries Management Area (KHFMA) – is the first place in Hawaii where fish stocks are managed with the specific goal of improving the health and resiliency of the coral reef itself, not just the fish.

Leading up to the establishment of the KHFMA, state monitoring results showed that coral cover in the reefs along this section of coastline had declined dramatically and that reefs were periodically overgrown by blooms of seaweed. The condition of the reef was particularly concerning in 2005 and 2006, when dense summer blooms of the alien seaweed Acanthophora spicifera appeared to be accelerating the ongoing declines in coral cover.

Survey data from this time showed that the herbivore fish biomass – which takes into account the total number of fishes and their sizes – within the area was low compared to similar habitats around other parts of Maui, particularly compared to marine reserves where fishes are protected from harvest.

Since January of 2008, the state Division of Aquatic Resources has partnered with, first, the University of Hawaii, and then the National Oceanic & Atmospheric Administration’s Pacific Islands Fisheries Science Center to conduct comprehensive monitoring of the coral reef areas within what is now the KHFMA. Those surveys involve detailed fish and habitat surveys conducted twice per year within the KHFMA and in some nearby areas just outside of the reserve boundaries.

A comparison of the reef substrate showing mats of seaweed and turf algae prior to the Kahekili Herbivore Fisheries Management Area going into effect, and then the open space and coverings of crustose coralline algae seven years following the area’s designation. PHOTOS BY THE HAWAII DEPARTMENT OF LAND AND NATURAL RESOURCES, DIVISION OF AQUATIC RESOURCES.

Results of these assessments are very promising. At the end of 2016, seven years following the management area designation, there were clear signs that important grazing fishes are increasing in size and numbers.

Parrotfishes have shown a nearly 170 percent increase in biomass (total weight of parrotfish per square meter of habitat), and surgeonfishes have experienced a more moderate 24 percent increase in biomass.

More importantly, however, the substrate, or surface of the reef base, appears to be changing in some critical ways.

The mats of seaweed and the covering of algal turf (fuzzy covering of small filamentous seaweeds) that once dominated the area have been replaced by large areas of crustose coralline algae (the purple and pink crusts of calcified seaweed). Corals tend to thrive in areas of high crustose algae.

Juvenile corals prefer to settle on reefs with high crustose algal cover, and corals also tend to grow faster when they are not competing for space with thick algal turfs and seaweeds. Living coral cover has been slower to respond.

The good news, however, is that the earlier declines in coral cover have stopped, and there are signs of recovery. Corals grow relatively slowly, so recovery takes time, but the positive impacts of herbivore protection at the KHFMA have greatly improved conditions for local corals to thrive.

Maui residents and visitors will have the opportunity to learn more about the KHFMA at the annual Ridge to Reef Rendezvous, a free, family-friendly community event featuring food, fun, music and prizes. The event will include a Keiki Fishing Tournament, a scavenger hunt for all ages and a Haunted Reef to explore.

Come learn more about this important management area and other actions being taken both in the water and on land to help protect the coral reefs of West Maui and throughout the state – and how you can get involved!

The theme of this year’s event is “Ocean Optimism.” Join scientists, managers and local conservation groups on Oct. 28 at Kahekili Beach Park (Old Airport Beach) in North Kaanapali from 9 a.m. to noon (note that the Keiki Fishing Tournament’s start time is 8 a.m.).

Join us for additional events leading up to the Ridge to Reef Rendezvous, including a Science Night focused on water quality at Kohola Brewery on Wednesday, Oct. 25, at 6:30 p.m. (ages 21 and up), and a special screening of the award-winning film “Chasing Coral,” followed by a Q&A panel of reef researchers, starting at 6 p.m. at Whalers Village on Friday, Oct. 27.

For more information, visit www.facebook.com/WestMauiKumuwai or call (808) 283-1631.