The few dozen commercial longliners who targeted tuna near Papahanaumokuakea Marine National Monument before its expansion in 2016 lost about 9% of their revenue in the subsequent 16 months, according to a new study.

About 38 of the 150-vessel fleet based in Honolulu fished close to the monument’s boundaries around the Northwestern Hawaiian Islands with any regularity. But for those operators, the expansion brought their revenue down to $71,164 per trip compared to $76,385 on average before President Barack Obama quadrupled the monument’s size, the study says.

For the majority of longliners who didn’t fish around the monument to begin with, their revenues increased during the same time period.

The study by Hing Ling Chan, “Economic impacts of Papahanaumokuakea Marine National Monument expansion on the Hawaii longline fishery,” was published Feb. 14 in ScienceDirect.

“One likely reason for the negative impacts is that longline fishers who previously fished inside the (monument expansion area) are still in the process of becoming more efficient in finding areas with comparable productivity relative to those found in their traditional fishing grounds,” the study says.

Catch effort increased about 7%, contributing to the $3.5 million loss in revenue that this group of fishermen experienced in the 16 months following the expansion.

“In the longer term, when longline fishers find productive fishing areas outside the MEA, they will likely become more efficient and the negative economic impacts have the potential to decline,” the study says.

The study says it allows fishery managers “to strategize policies to alleviate the economic impacts on the fleet.”

A separate study, released Thursday, concluded that Obama’s massive expansions of two marine national monuments — Papahanaumokuakea and the Pacific Remote Islands — did not cause any of the alleged financial harm that Hawaii’s longline tuna fishermen had threatened would happen.

It found that the fleet’s overall revenue from 2014 to 2017 was 13.7% higher than from 2010 to 2013.

Mark Fitchett, the pelagic fisheries scientist for the Western Pacific Regional Fishery Management Council, said Friday that the study that found no harm to Hawaii’s tuna fishermen failed to consider oceanographic scenarios which actually increase fish recruitment and it didn’t take into account information from the latest stock assessment.

He said the council’s scientific advisory committee is planning a rebuttal.