Overfishing is being fingered as the chief cause of diminishing numbers of reef fish in Hawaii’s nearshore waters in a comprehensive new study.

The conclusion is drawn from an analysis of data collected from multiple agencies and dating back to the year 2000, representing more than 25,000 in-water surveys at 6,500 sites across the 1,500-mile island chain.

“It’s the largest collection of data for any single archipelago,” said lead author Alan Friedlander, a University of Hawaii marine biologist and chief scientist of National Geographic’s Pristine Seas program.

The study, published in the journal Aquatic Conservation, does not absolve other factors suspected of harming reef populations, including runoff, nutrients and physical damage to reefs.

But it clearly points to nearshore fishing — or rather the excess of it — as the primary culprit, and suggests that if Hawaii wants to see healthy reefs and sustainable fisheries over the long term, improvements are needed in how these areas are managed.

“The trends are alarming, especially in the most populous places,” said co-author Eric Conklin, marine science director for the Nature Conservancy.

The data indicate that in the waters off Oahu and Maui, areas of greater human population, the number of food fish species, including uhu, omilu and kala, is only a small fraction of the same species on remote reefs adjacent to smaller human populations, such as north Molokai, Kahoolawe and Niihau.

At the same time, the total amount of nonfood fish species, including damselfish, butterflyfish and hinalea, is similar just about everywhere, including areas with large human populations and considerable fishing pressure.

The study also compared food fish populations between the main and northwestern islands. There were nearly three times more food fish in the Northwestern Hawaiian Islands than in the main islands, and nearly 10 times more than off Oahu and parts of Maui.

Furthermore, an analysis of 35 prized food fish species showed that the presence of 14 of those species in the main islands was less than a quarter of what they are in the far-flung islands to the northwest.

Friedlander said the marine environment in the main Hawaiian Islands has reached a critical juncture. Many key food fish species have declined by more than 75 percent, he said, a rate that can’t persist if islanders want to continue to fish and eat reef fish.

Asked who’s to blame, Friedlander responded, “1.3 million people.”

As many as a third of Hawaii residents identify themselves as fishers, he said, and commercial fisheries account for only 10 percent of the nearshore fishing harvest.

Friedlander said the problem is exacerbated by the fact that the state spends relatively little on managing its vast marine resources. Not only is the state Department of Land and Natural Resources poorly funded, he said, but so is its enforcement of state marine rules.

Friedlander said the problem needs to be tackled from a holistic view looking at a variety of solutions.

Among the potential solutions is establishing marine protected areas, described by the scientist as a proven way to restore declining fish populations. However, he cautioned, such preserves need to be well designed, effectively managed and large enough to protect valued species, allowing them to mature and produce plenty of offspring.

Another proven solution is community-managed fisheries, like the ones recently established in Haena on Kauai and Kaupulehu in West Hawaii. These areas can harbor fish in numbers equal to or even greater than no‐take reserves, according to the paper.

Conklin said that with oceans warming, corals bleaching and waters getting more acidic, it is it doubly important now to figure out how to restore Hawaii’s reefs and fisheries to give them the best chance into the future.

The healthier the reefs, the better they will be able to resist the effects of climate change, or to recover from events like the mass bleaching event of 2015, he said.

Last year Gov. David Ige established a goal of having 30 percent of Hawaii’s waters effectively managed by the year 2030.

“This study is a first step to get the discussion going,” Friedlander said. “At the end of the day, how to address the problem is a collective decision by the local community.”

In compiling the data, Friedlander’s graduate student, Mary Donovan, spent a year working with the data to calibrate the numbers.

Most of the fish surveys came from the National Oceanic and Atmospheric Administration, the Nature Conservancy, state Division of Aquatic Resources, UH’s Hawaii Institute of Marine Biology and Friedlander’s lab.

Other co-authors include Donovan and Kostantinos Stamoulis of the UH Fisheries Ecology Research Lab, Ivor Williams of NOAA’s Pacific Islands Fisheries Science Center, Eric Brown of Kalaupapa National Historical Park, Edward DeMartini and Kuulei Rodgers of the Hawaii Institute of Marine Biology, and Russell Sparks and William Walsh of the Division of Aquatic Resources.