West Maui reefs rich in data

New study shows coral cover, fish weight slightly higher than average

West Maui reefs are unrivaled among other local areas when it comes to data, according to researchers, which is why a swath of nearly 24 acres — from Honoapi‘ilani Highway’s Pali Tunnel to Lipoa Point — was chosen over other coastlines for decades of reef study.

“The reefs of West Maui . . . had a lot of data, more than most areas,” Emily Fielding, The Nature Conservancy’s Maui marine program director, said Thursday. “And we are working closely with community and agency partners who need this kind of data to make decisions about reef management.”

Using information collected by public and private organizations at more than 2,600 West Maui sites from 1999 to 2019, The Nature Conservancy recently compiled “Atlas of the Reefs of West Maui,” according to a news release.

The atlas details changes in abundance, biomass and diversity in area marine life.

Fielding said one standout from the data is that coral cover and the combined weight of all fish in West Maui were only slightly higher than the statewide average.

“The statewide average reflects decades of declines,” she said. “Likewise, West Maui reefs have declined over the past 20 years due to sedimentation and land-based pollution, overharvest, climate change impacts, such as sea surface temperature rise as we saw in the 2015 and 2019 coral bleaching events.”

She added that the good news is that there’s room to improve.

“With community support, marine management and pollution reduction, our reefs can recover,” Fielding said.

Location-specific highlights include the following:

≤ Hanaka‘o‘o: Reef resources were highly variable and of mixed quality, with low coral cover and richness of species at the southern end and higher coral cover at the northern end compared to the rest of West Maui.

≤ Honolua: The area had below-average coral cover yet high benthic (residing at the bottom) diversity when compared to West Maui averages. The effect of marine-protected areas was detectable in reef fish communities, with the Honolua-Mokule‘ia

Marine Life Conservation District having the highest biomass of the largest prized food fishes, which produce the most and highest quality eggs for seeding the next generatioon.

≤ Kahana: Coral cover was the lowest in this area. Total fish biomass was medium high and the biomass of prized food fish was average.

≤ Kahekili: Reefs in the area had high coral cover relative to the statewide average but were a “mixed bag” on fish. The North Ka‘anapali reef tract had above-average resources, likely because it falls within a management area, but the Mahinahina reef tract was below average for total fish and resource fish biomass.

≤ Lahaina: Lahaina’s reef tract is heavily affected by fishing and has obvious impacts from land-based sources of pollution, yet patches of benthic and reef resources were above average for the region.

≤ Launiupoko: Insufficient data from the area created a “survey gap” and should be treated cautiously due to low sampling, the report said. The limited results showed medium-low to average abundance, biomass and diversity, as well as medium-low coral cover.

≤ Olowalu: Comprised of three reef tracts, the Olowalu survey area ranged from low to high when compared to regional averages. The centermost Olowalu reef tract ranked among the best reef areas in the region, with high coral cover and benthic diversity and medium-high total fish and resource fish biomass.

“Atlas of the Reefs of West Maui” will help various groups direct limited resources to priority areas. The atlas will also inform strategies to reduce reef pressures tied to land-based pollution, unsustainable ocean resource harvesting, warming climate and other challenges.

“The intent for the atlas is to help federal, state and community partners strengthen coastal management in West Maui,” Eric Conklin, marine science director for The Nature Conservancy’s Hawaii chapter, said in the news release. “It is already informing local efforts to manage and restore West Maui watersheds, Honolua Bay and an area stretching south from Ka‘anapali.”

The atlas was designed to provide West Maui community groups and government agencies such as state Department of Land and Natural Resources’ Division of Aquatic Resources with a “shared understanding of how, when and where the reefs have changed so that they can develop targeted and effective strategies to reduce local pressures, increase reef resilience and restore reef fisheries,” the news release said.

“The atlas provides a clear picture of the changes in West Maui’s reefs and fish populations,” Russell Sparks, DLNR Division of Aquatic Resources biologist said in the news release. “Understanding these changes is helping us and our community partners develop effective management plans to restore these resources and achieve our shared goal of effectively protecting 30 percent of nearshore areas by 2030.” ■

MAUI DIGITAL IMAGES photo An aerial shot of West Maui’s Na Papalimu O Pi‘ilani shows reef area rich with data for researchers. Decades of reef studies were compiled recently by The Nature Conservancy in “Atlas of the Reefs of West Maui.”

RYAN CARR photo A diver with The Nature Conservancy surveys West Maui reefs. Decades of reef studies were compiled recently by The Nature Conservancy in “Atlas of the Reefs of West Maui,” which will help government and community groups with reef management.