Study finds Big Island reefs in decline
By ERIN MILLER
A recent Hawaii Department of Land and Natural Resources study of reef fish at Puako and Pauoa shows a “drastic decline” in the populations of both bays, a marine biologist says.
The study may focus on those two South Kohala bays, but William Walsh, a biologist with the department’s Division of Aquatic Resources, said it is consistent with data from studies in other areas along the West Hawaii coastline.
“We’re seeing the same sort of declines in the total number of fishes” at Keei and Honaunau in South Kona, too, Walsh said, adding South Kona and South Kohala are fairly disparate environments. “These are areas that aren’t the most urbanized (either).”
The University of Hawaii studied Puako and Pauoa extensively from 1979 to 1981, Walsh said. To get an accurate understanding of the bays’ fish and coral declines, Walsh’s team resurveyed the bays in 2007 and 2008 using the same methods as the team nearly three decades earlier. Walsh recently wrote a new report incorporating that data, and more, as part of a peer-reviewed paper on the fishery decline.
“Over that 28-year period, whatever you were looking at, it’s gone downhill dramatically,” he added.
According to Walsh’s latest report, the total abundance of all fish species declined 43 percent to 69 percent at Puako. The variations in decline reflect the different areas of the bay surveyed. Of the 35 most abundant reef fish — which make up 92 percent of fish present in the initial surveys — 31 declined in abundance. The decline ranged from 9 percent fewer yellow tang to a 98 percent decline in the mamo, or Hawaiian sergeant, population. Kole, or goldring surgeonfish, populations at Puako dropped 61 percent; wekea, or yellowstripe goatfish, dropped 86 percent; and the Achilles tang population dropped 97 percent.
At Pauoa, the declines ranged from 49 percent to 76 percent, the report said. Again, 31 of 35 species showed population decreases, from 6 percent in the bird wrasse population to a complete disappearance of the threespot chromis, the report said. Kole decreased by 71 percent and mamo dropped by 99 percent.
One increase at Pauoa, Walsh said, was a 14 percent growth in the yellow tang population there. Between Puako and Pauao, that species had a net gain, he added.
The decreases weren’t limited just to fish, Walsh said. Coral cover dropped by 35 percent at Puako and 21 percent at Pauoa. Crustose coralline algae — the precursor to coral growth — was down 64 percent at Puako and 87 percent at Pauoa.
“The loss of crustose coralline algae has huge implications for the potential regeneration of these coral reefs,” the report said.
Walsh noted the studies at Puako in the early 1980s resulted in the community getting the bay designated as a Fishery Management Area in 1985. Pauoa was made a fish replenishment area in 2000, bringing additional protections there. He said the fish declines in the bay aren’t evidence that limits on fishing in the bay have failed. He said he wonders how much lower the populations would have dropped if they had not been protected.
Walsh was planning to make an informational presentation to the Board of Land and Natural Resources today on a proposed fishery management rules package for West Hawaii. Recently struck from that package, he said, was a ban on scuba spearfishing. Going forward with that ban would remove one stressor from the reefs, he said.
But to fully address the reef concerns, Walsh said ocean users and state and county officials need to look at all the stressors — not just overfishing, but sediment on land that runs into the reefs, for example, or the runoff of chemicals from mauka areas to the shoreline.
Walsh said he doesn’t know for certain if his latest study and report will convince the land board, or DLNR Chairman William Aila, who removed the scuba spearfishing ban from the rules package citing a lack of information, to implement stronger reef protections.
“That is the ultimate question,” Walsh said. “There are people, decisionmakers, in denial. They will not accept changes in behavior.”
Email Erin Miller at firstname.lastname@example.org.
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