The expansion of two large U.S. marine protected areas (MPAs) in the Pacific Ocean had no measurable economic effects on the fishing industry, according to a study published in the journal Nature Communications, one of only a few studies to apply rigorous scientific methods to this issue.
The authors looked at longline commercial fishing by the Hawaii fleet around two of the largest protected areas on earth: The Pacific Remote Islands Marine National Monument (PRI), south and east of Hawaii, which was expanded in 2014, and the Papahānaumokuākea Marine National Monument (PMNM) in the Northwestern Hawaiian Islands, which was enlarged in 2016. The expansions quadrupled the size of each of these MPAs, which together prohibit commercial fishing and oil and gas exploration across more than 2.7 million square kilometers (around 1.1 million square miles) of ocean.
Prior to the enlargement of both PRI and PMNM, the fishing industry warned that expanding the MPAs would reduce catch and increase travel costs for fishermen, harming them and Hawaii retail seafood markets. This study looked for evidence of such negative effects in a major component of the industry, the Hawaii longline tuna fishery.
Past studies on the impacts of MPAs on fishing typically compared catch, revenue, or other metrics before and after a protected area was established (or expanded). But that approach failed to account for changes in other important factors, such as environmental conditions or the abundance of the targeted fish species; for example, if abundance increases during the time frame of a study but isn’t considered in the research, the results might not show the true effects of an MPA on fishermen.
To account for these factors, researchers in this study used one control fishery for each MPA—for PRI, the Hawaii longline swordfish fleet; and for PMNM, the American Samoa longline albacore tuna fleet—neither of which were influenced by the expansions. Although neither control fleet specifically targeted yellowfin or bigeye tuna, researchers used data on the incidental catch of these tuna species to make comparisons.
To assess if enlarging the MPAs affected fishing profitability, the researchers compiled four metrics of “catch per unit effort.” These metrics serve as proxies for profitability because they relate fishing costs to catch. For example, they estimated the total catch obtained per mile traveled, per fishing trip, per fishing event, and per 1,000 hooks placed in the water.
The study found that total catch and revenue were higher after the monuments were expanded. In fact, according to publicly available data, the Hawaii longline fleet recorded its highest-ever revenue in 2016 and 2017, and average revenue for 2014-17 was 14 percent higher than in 2010-13. Both control fisheries exhibited similar trends, suggesting that—for the main fishery studied—other factors were not masking a negative effect of the MPAs on fishing. In fact, the researchers found no net impact on profitability following the PMNM expansion and increased profitability following the PRI expansion. One caveat is that the researchers assessed the economic effects only on the fleet as a whole, not on individual vessels. Another is that the study evaluated effects only on the Hawaii longline tuna fleet, and did not include other vessels or fleets in the analysis.
“Our results show that remote protected areas might be an extremely low-cost method of protecting biodiversity,” says John Lynham, professor of economics at the University of Hawaii at Mānoa and lead author on the paper. “An area larger than Argentina has been permanently protected with zero or extremely small costs resulting from the closure of these fishing grounds.”
The study may be helpful to policymakers as they consider MPAs as a tool to conserve biodiversity. Scientists should pay attention, too: With this more-rigorous research approach, it is no longer necessary to rely on anecdotal evidence on the economic effects of MPAs on fishing.
Jim Palardy is a project director for environmental research and science with The Pew Charitable Trusts.