Significance: Understanding how social dynamics drive outcomes in environmental systems is critical to advancing global sustainability. We link comprehensive data on fishers’ information-sharing networks and observed fishing behaviors to demonstrate that social networks are tied to actions that can directly impact ecological health. Specifically, we find evidence that the propensity for individuals to share information primarily with others most similar to themselves creates segregated networks that impede the diffusion of sustainable behaviors—behaviors that could have mitigated the incidental catch of over 46,000 sharks in a single commercial fishery between 2008 and 2012. Our results suggest having a better understanding of social structures and bolstering effective communication across segregated networks has the potential to contribute toward more sustainable environmental outcomes.

The creation of marine reserves is often controversial. For decisionmakers, trying to find compromises, an understanding of the timing, magnitude, and incidence of the costs of a reserve is critical. Understanding the costs, in turn, requires consideration of not just the direct financial costs but also the opportunity costs associated with reserves. We use a discrete choice model of commercial fishermen’s behavior to examine both the short-run and long-run opportunity costs of marine reserves. Our results can help policymakers recognize the factors influencing commercial fishermen’s responses to reserve proposals. More generally, we highlight the potential drivers behind the political economy of marine reserves.

Previous research has cast doubt on the potential for marine protected areas (MPAs) to provide refuge and fishery spillover benefits for migratory species as most MPAs are small relative to the geographic range of these species. We test for evidence of spillover benefits accruing from the world’s largest fully protected MPA, Papahānaumokuākea Marine National Monument. Using species-specific data collected by independent fishery observers, we examine changes in catch rates for individual vessels near to and far from the MPA before and after its expansion in 2016. We find evidence of spillover benefits for yellowfin ( Thunnus albacares ) and bigeye tuna ( Thunnus obesus ).

Two of the largest protected areas on earth are U.S. National Monuments in the Pacific Ocean. Numerous claims have been made about the impacts of these protected areas on the fishing industry, but there has been no ex post empirical evaluation of their effects. We use administrative data documenting individual fishing events to evaluate the economic impact of the expansion of these two monuments on the Hawaii longline fishing fleet. Surprisingly, catch and catch-per-unit-effort are higher since the expansions began. To disentangle the causal effect of the expansions from confounding factors, we use unaffected control fisheries to perform a difference-in-differences analysis. We find that the monument expansions had little, if any, negative impacts on the fishing industry, corroborating ecological models that have predicted minimal impacts from closing large parts of the Pacific Ocean to fishing.

Global tuna fisheries are valued at more than $40 billion, with the majority of this value derived from purse seine fisheries. Recently created large-scale marine protected areas are potentially big enough to protect highly migratory species such as tuna, possibly leading to increases in abundance (a conservation benefit) and consequent spillover near protected area boundaries (an economic benefit). Using publicly available data from nine large-scale marine protected areas across the Pacific and Indian oceans, we find that catch-per-unit-effort in tuna purse seine fisheries has increased by an average of 12 to 18% near protected area boundaries, and this increase declines with distance from the boundaries. The increase is larger for bigeye tuna ( Thunnus obesus ) than for skipjack tuna ( Katsuwonus pelamis ), in line with fisheries science simulation models.