Unregulated fishing practices have left 75 percent of reef fishes depleted or in critical condition around the main Hawaiian Islands, according to new data on the state of Hawai'i's reefs.

The declining fish stock is disrupting the ecological balance of many reefs, which rely on herbivorous fish to keep algal growth in check, researchers say.

"We have a significant fishing problem in Hawai'i," said Alan Friedlander, fisheries ecologist with the Oceanic Institute. "Many species have been depleted, and there are appropriate things that need to be done in different areas to ensure the sustainability of our reefs."

Friedlander, along with marine ecologist Eric Brown of the Kalaupapa National Historical Park, presented the findings of a report titled "The State of Coral Reef Ecosystems of the Main Hawaiian Islands" today at the Waikiki Aquarium.

According to the report, overfishing is just one of a growing list of pressures Hawai'i's coral reefs currently face, including rising sea temperatures, coastal development, pollution and invasive species. Nonetheless, Hawai'i's reefs are still relatively healthy compared to reefs in the Caribbean and the Atlantic.

The report, part of a larger effort by the National Oceanic and Atmospheric Administration to study the state of reefs in the United States. and various Pacific regions, draws attention to Hawai'i's declining populations of targeted species of fish such as ulua, kumu, 'o'io and moi.

Researchers examined population trends for 55 reef fish species in the main Hawaiian Islands compared to the virtually unfished Northwestern Hawaiian Islands, which served as a baseline. They found that 42 percent of these species were in critical condition and 33 percent were depleted. Another 11 percent were below desired population levels, while just 2 percent were abundant.

"Some of these species are highly important as native food fishes," said Friedlander. They also play critical roles within Hawai'i's unique reef ecosystems, he said.

Without herbivorous fish grazing on reef algae, high levels of algae could smother and kill corals. In addition, many of these species cannot be replaced, should they become depleted.

"We have a lot of endemism here. Some of these species are found here and nowhere else in the world. That's something that is very important to consider," Brown said.

Of the more than 7,000 marine plants and animals that inhabit Hawai'i's reefs, approximately 25 percent are found only in the Islands.

The lack of local management, poor enforcement of existing regulations and harmful fishing methods such as gill nets have all contributed to smaller fish populations, according to the report.

In addition, researchers also cited improved technology and an increase in the non-commercial catch of reef species by recreational and subsistence fishers as factors affecting the declining fish stock.