Impact of two of the world's largest protected areas on longline fishery catch rates

Evidence of spillover benefits from large-scale marine protected areas to purse seine fisheries

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.

Fishery Management Enforcement Gradients to Achieve Fishery Goals

Marine protected areas (MPAs) can allow some fish populations to rebuild within their borders in areas impacted by overfishing, but the effectiveness of reserves is highly dependent on how effectively fishing mortality is controlled, which in turn depends on the level of fishery management implementation. In Cuba’s Gardens of the Queen MPA, the largest in the Caribbean, a variety of fishery management measures have been implemented to ensure the social, economic, and political viability of protecting such a large area. Here, we evaluate the biological response, in terms of fish density and the biomass of commercially valuable and ecologically important reef fish species, to a spatial gradient of fishery management enforcement, in terms of fish density and biomass, of commercially valuable and ecologically important reef fish species. The enforcement gradient is characterized by the level of protection, fishing effort, patrolling effort, distance to the nearest fishing port, and fishing intensity. Fish density and biomass were estimated from visual scuba surveys. Areas with higher levels of enforcement support higher levels of average biomass (up to 1378 kg/ha) and density (up to 2367 indv./ha) of commercially important fishes in comparison to areas with very low or no enforcement (estimates of 757 kg/ha average biomass and 1090 indv./ha average density, respectively). These fish density and biomass levels can serve as proxies in the development of harvest control rules that adjust fishing pressure according to the ratio of fished density or biomass to unfished density or biomass, through the use of the MPA Density Ratio method.

Global expansion of marine protected areas and the redistribution of fishing effort

The expansion of marine protected areas (MPAs) is a core focus of global conservation efforts, with the "30x30" initiative to protect 30% of the ocean by 2030 serving as a prominent example of this trend. We consider a series of proposed MPA network expansions of various sizes, and we forecast the impact this increase in protection would have on global patterns of fishing effort. We do so by building a predictive machine learning model trained on a global dataset of satellite-based fishing vessel monitoring data, current MPA locations, and spatiotemporal environmental, geographic, political, and economic features. We then use this model to predict future fishing effort under various MPA expansion scenarios compared to a business-as-usual counterfactual scenario that includes no new MPAs. The difference between these scenarios represents the predicted change in fishing effort associated with MPA expansion. We find that regardless of the MPA network objectives or size, fishing effort would decrease inside the MPAs, though by much less than 100%. Moreover, we find that the reduction in fishing effort inside MPAs does not simply redistribute outside-rather, fishing effort outside MPAs would also decline. The overall magnitude of the predicted decrease in global fishing effort principally depends on where networks are placed in relation to existing fishing effort. MPA expansion will lead to a global redistribution of fishing effort that should be accounted for in network design, implementation, and impact evaluation.

Evaluating ecological benefits of oceanic protected areas

Oceans beyond the continental shelf represent the largest yet least protected environments. The new agreement to increase protection targets to 30% by 2030 and the recent United Nations (UN) High Seas Treaty try to address this gap, and an increase in the declaration of oceanic Marine Protected Areas (oMPAs) in waters beyond 200 m in depth is likely. Here we find that there is contradictory evidence concerning the benefits of oMPAs in terms of protecting pelagic habitats, providing refuge for highly mobile species, and potential fisheries benefits. We discover a mismatch between oMPA management objectives focusing on protection of pelagic habitats and biodiversity, and scientific research focusing on fisheries benefits. We suggest that the solution is to harness emerging technologies to monitor inside and outside oMPAs.

Anticyclonic eddies aggregate pelagic predators in a subtropical gyre

Ocean eddies are coherent, rotating features that can modulate pelagic ecosystems across many trophic levels. These mesoscale features, which are ubiquitous at mid-latitudes¹, may increase productivity of nutrient-poor regions^2,3, accumulate prey⁴ and modulate habitat conditions in the water column⁵. However, in nutrient-poor subtropical gyres-the largest marine biome-the role of eddies in modulating behaviour throughout the pelagic predator community remains unknown despite predictions for these gyres to expand⁶ and pelagic predators to become increasingly important for food security⁷. Using a large-scale fishery dataset in the North Pacific Subtropical Gyre, we show a pervasive pattern of increased pelagic predator catch inside anticyclonic eddies relative to cyclones and non-eddy areas. Our results indicate that increased mesopelagic prey abundance in anticyclone cores^4,8 may be attracting diverse predators, forming ecological hotspots where these predators aggregate and exhibit increased abundance. In this energetically quiescent gyre, we expect that isolated mesoscale features (and the habitat conditions in them) exhibit primacy over peripheral submesoscale dynamics in structuring the foraging opportunities of pelagic predators. Our finding that eddies influence coupling of epi- to mesopelagic communities corroborates the growing evidence that deep scattering layer organisms are vital prey for a suite of commercially important predator species⁹ and, thus, provide valuable ecosystem services.

Fishing activity before closure, during closure, and after reopening of the Northeast Canyons and Seamounts Marine National Monument

Evaluation of the economic impacts of marine protected areas is hampered by the fact that it is impossible to observe what would have happened if the protected area had never been closed to fishing (the counterfactual). Catch reports and vessel tracks are used to perform an analysis of the potential negative economic impacts of establishing the Northeast Canyons and Seamounts Marine National Monument (located off the east coast of the United States of America) on three commercially important fisheries that were identified as having potential to be harmed. I conclude that there was little to no negative impact on any of the fisheries. I also test for, but find no evidence of, a Blue Paradox effect. Due to political factors largely unrelated to fisheries status, the protected area was reopened to commercial fishing on June 5th, 2020. I use this event, which was reversed sixteen months later, to test whether there were any economic benefits from reopening. I do not observe an increase in catch, a reduction in distance traveled, or an increase in relative fishing effort inside the protected area (compared to historical trends), consistent with the post-closure findings.

Protecting the global ocean for biodiversity, food and climate

The ocean contains unique biodiversity, provides valuable food resources and is a major sink for anthropogenic carbon. Marine protected areas (MPAs) are an effective tool for restoring ocean biodiversity and ecosystem services1,2, but at present only 2.7% of the ocean is highly protected3. This low level of ocean protection is due largely to conflicts with fisheries and other extractive uses. To address this issue, here we developed a conservation planning framework to prioritize highly protected MPAs in places that would result in multiple benefits today and in the future. We find that a substantial increase in ocean protection could have triple benefits, by protecting biodiversity, boosting the yield of fisheries and securing marine carbon stocks that are at risk from human activities. Our results show that most coastal nations contain priority areas that can contribute substantially to achieving these three objectives of biodiversity protection, food provision and carbon storage. A globally coordinated effort could be nearly twice as efficient as uncoordinated, national-level conservation planning. Our flexible prioritization framework could help to inform both national marine spatial plans4 and global targets for marine conservation, food security and climate action.

Antarctic krill fishery effects over penguin populations under adverse climate conditions: Implications for the management of fishing practices

Fast climate changes in the western Antarctic Peninsula are reducing krill density, which along with increased fishing activities in recent decades, may have had synergistic effects on penguin populations. We tested that assumption by crossing data on fishing activities and Southern Annular Mode (an indicator of climate change in Antarctica) with penguin population data. Increases in fishing catch during the non-breeding period were likely to result in impacts on both chinstrap (Pygoscelis antarcticus) and gentoo (P. papua) populations. Catches and climate change together elevated the probability of negative population growth rates: very high fishing catch on years with warm winters and low sea ice (associated with negative Southern Annular Mode values) implied a decrease in population size in the following year. The current management of krill fishery in the Southern Ocean takes into account an arbitrary and fixed catch limit that does not reflect the variability of the krill population under effects of climate change, therefore affecting penguin populations when the environmental conditions were not favorable.

Evidence that spillover from Marine Protected Areas benefits the spiny lobster (Panulirus interruptus) fishery in southern California

Marine Protected Areas (MPAs) are designed to enhance biodiversity and ecosystem services. Some MPAs are also established to benefit fisheries through increased egg and larval production, or the spillover of mobile juveniles and adults. Whether spillover influences fishery landings depend on the population status and movement patterns of target species both inside and outside of MPAs, as well as the status of the fishery and behavior of the fleet. We tested whether an increase in the lobster population inside two newly established MPAs influenced local catch, fishing effort, and catch-per-unit-effort (CPUE) within the sustainable California spiny lobster fishery. We found greater build-up of lobsters within MPAs relative to unprotected areas, and greater increases in fishing effort and total lobster catch, but not CPUE, in fishing zones containing MPAs vs. those without MPAs. Our results show that a 35% reduction in fishing area resulting from MPA designation was compensated for by a 225% increase in total catch after 6-years, thus indicating at a local scale that the trade-off of fishing ground for no-fishing zones benefitted the fishery.

Tracking the response of industrial fishing fleets to large marine protected areas in the Pacific Ocean

Large marine protected areas (MPAs) of unprecedented size have recently been established across the global oceans, yet their ability to meet conservation objectives is debated. Key areas of debate include uncertainty over nations' abilities to enforce fishing bans across vast, remote regions and the intensity of human impacts before and after MPA implementation. We used a recently developed vessel tracking data set (produced using Automatic Identification System detections) to quantify the response of industrial fishing fleets to 5 of the largest MPAs established in the Pacific Ocean since 2013. After their implementation, all 5 MPAs successfully kept industrial fishing effort exceptionally low. Detected fishing effort was already low in 4 of the 5 large MPAs prior to MPA implementation, particularly relative to nearby regions that did not receive formal protection. Our results suggest that these large MPAs may present major conservation opportunities in relatively intact ecosystems with low immediate impact to industrial fisheries, but the large MPAs we considered often did not significantly reduce fishing effort because baseline fishing was typically low. It is yet to be determined how large MPAs may shape global ocean conservation in the future if the footprint of human influence continues to expand. Continued improvement in understanding of how large MPAs interact with industrial fisheries is a crucial step toward defining their role in global ocean management.