When marine biologists started closely studying life on the reefs of the Northwestern Hawaiian Islands, one of the first things they noted was the amazing concentration of really big predators like sharks and jacks, or ulua.

And when Alan Friedlander, of the Oceanic Institute, and Edward DeMartini, of NOAA Fisheries, did some calculations, the results were even more impressive. They found that the big predators represented 54 percent of the total fish biomass in the Northwestern Hawaiian Islands, compared with just 3 percent in the main Islands.

The finding, and the conclusion that the predator dominance was a feature of a largely unfished ecosystem, helped make the case for the uniqueness of the more than 1,000 miles of Hawai'i that lies to the northwest of Kaua'i and Ni'ihau. And that helped lead to the establishment of the Papahanaumo-kuakea Marine National Monument.

But one could have asked whether the Hawaiian situation was somehow different from what's gone on elsewhere in the world.

Now a group of researchers has reported the same pattern in the Line Islands. Charlotte Stevenson, Laure S. Katz, Fiorenza Micheli, Barbara Block, Kimberly W. Heiman, Chris Perle, Kevin Weng and Robert Dunbar, of Stanford University, and Jan Witting, of the Sea Education Association, studied the differences between largely unfished Palmyra Atoll with the nearby reefs of Christmas and Fanning islands.

Their finding: Big predators were 56 percent of the fish biomass on Palmyra, but just 7 percent on Christmas and 3 percent on Fanning.

Not surprisingly, the total amount of fish biomass — a figure representing the weight of all the fish in a given area — was also similar when the Hawaiian situation was compared with that in the Line Islands.

In Hawai'i, there was 260 percent more fish in the northwestern section of the archipelago than in the main Islands. In the Line Islands, Palmyra has 428 percent more than Christmas and 299 percent more than Fanning.

Friedlander said the Line Islands research shows that the Papahanaumokuakea-Main Hawaiian Islands difference is not unique.

"I think this gives us a base line," he said. The examples of Papahanaumokuakea, Palmyra and also Kingman Reef, where Friedlander has worked, show what an undisturbed marine reef ecosystem looks like, and in preservation efforts, what to work toward.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766 or jant@honoluluadvertiser.com. Or call him at (808) 245-3074.