Biologist offers insights on reef fish

State biologist Bill Walsh offered two slightly different takes Thursday on the state of reef fish in West Hawaii at the Symposium on Kona’s Marine Ecosystem.

In the first, which focused on fish populations at Puako and nearby Pauoa, Walsh noted overall declines in numbers of fish. But in the second, Walsh offered a slightly more optimistic analysis that showed while the numbers of yellow tang in West Hawaii waters had declined since the 1970s, the population has been increasing for more than a decade and is nearing the highs recorded 40 years ago.

At Puako and Pauoa, “across the board, 31 of 35 species have decreased,” Walsh said during the earlier talk. “There’s really no difference. Everything is decreasing there.”

The number of herbivores that live on the reefs has also declined, as has the number of certain kinds of coral.

Overall, the fish population at the two reefs is 57 percent lower than it was in the 1970s, Walsh said.

While people opposed to the fishing collection trade might point to that business as the root of the problem at the bays, Walsh said the situation is more complex than that.

So what is happening? Walsh offered a few insights.

“The population of Hawaii County has increased 140 percent since 1975,” he said, adding that South Kohala in particular has undergone major development, which bring with them golf courses, condos and a large amount of human effluent that is in some places disposed of through injection wells.

Waste that goes into the ground in West Hawaii is moved by underground water sources, he said.

“Whatever you put there, it doesn’t stay there,” Walsh said. “It goes makai.”

In Puako, one person is spearheading efforts to move sewage disposal away from cesspools, he added.

Visitors to Puako, even those from other Hawaiian islands, are still impressed with the reef there, Walsh said.

“It’s a really nice reef,” he said. “They are great. But they were greater.”

Later in the day, though, Walsh’s comments were more positive. Across the entire Kona Coast, when scientists return to specific sites, they are finding that fish populations are increasing in areas where fish reserve areas have been created. Those reserve areas prohibit the collection of fish for the aquarium trade in about 30 percent of West Hawaii waters. And rules last year limited the take to just 40 species, referred to as the white list species.

For example, yellow tang, which are one of the two most collected aquarium fish, have seen populations increase 10 percent in marine protected areas and 65 percent in fish reserve areas since 1999, Walsh said. The population in open areas is about 5 percent lower than in 1999, which Walsh said was not statistically significant.

One interesting note, he said, was what happened to the yellow tang populations in open areas bordering the protected areas. There, the populations were slightly higher than the open areas as a whole, thanks likely to spillover from the protected areas.

“For every cloud, there is a ray of sunlight that comes through,” Walsh said. “Set aside enough management areas and you can change (the population) across the entire coast.”