Predicting impact to assess the efficacy of community-based marine reserve design

During the planning phase the efficacy of different strategies to manage marine resources should ultimately be assessed by their potential impact, or ability to make a difference to ecological and social outcomes. While community-based and systematic approaches to establishing marine protected areas have their strengths and weaknesses, comparisons of their effectiveness often fail to explicitly address potential impact. Here, we predict conservation impact to compare recently implemented community-based marine reserves in Tonga to a systematic configuration specifically aimed at maximizing impact. Boosted regression tree outputs indicated that fishing pressure accounted for ∼24% of variation in target species biomass. We estimate that the community-based approach provides 84% of the recovery potential of the configuration with the greatest potential impact. This high potential impact results from community-based reserves being located close to villages, where fishing pressure is greatest. These results provide strong support for community-based marine management, with short-term benefits likely to accrue even where there is little scope for systematic reserve design

Spatial subsidies drive sweet spots of tropical marine biomass production

Spatial subsidies increase local productivity and boost consumer abundance beyond the limits imposed by local resources. In marine ecosystems, deeper water and open ocean subsidies promote animal aggregations and enhance biomass that is critical for human harvesting. However, the scale of this phenomenon in tropical marine systems remains unknown. Here, we integrate a detailed assessment of biomass production in 3 key locations, spanning a major biodiversity and abundance gradient, with an ocean-scale dataset of fish counts to predict the extent and magnitude of plankton subsidies to fishes on coral reefs. We show that planktivorous fish-mediated spatial subsidies are widespread across the Indian and Pacific oceans and drive local spikes in biomass production that can lead to extreme productivity, up to 30 kg ha−1 day−1. Plankton subsidies form the basis of productivity “sweet spots” where planktivores provide more than 50% of the total fish production, more than all other trophic groups combined. These sweet spots operate at regional, site, and smaller local scales. By harvesting oceanic productivity, planktivores bypass spatial constraints imposed by local primary productivity, creating “oases” of tropical fish biomass that are accessible to humans

Spatio-Temporal Variation in Growth Performance and Condition of the Winged Pearl Oyster Pteria penguin

Environmental conditions can strongly influence the growth performance of pearl oysters and affect pearl farm production schedules. Growth and condition index (CI) of two age cohorts of Pteria penguin were measured for 13 months to investigate differences in growth performance between four culture sites within the northern (Vava’u) and southern (Tongatapu) island groups of the Kingdom of Tonga. Environmental conditions were also measured at culture sites and used to explore potential effects on oyster growth and condition. Between island groups, growth performance of P. penguin was superior at northern sites and was most strongly related to higher water temperatures at these sites. Within the southern island group, growth performance varied significantly between sites and may be driven by differences in wave energy. Monthly growth rates (GM) of P. penguin also showed significant temporal variation related to age and environmental conditions. This study demonstrated significant variation in the growth performance of P. penguin at latitudinal and local scales and suggests that in oligotrophic marine environments with minimal terrestrial inputs, such as Tonga, water temperature and wave exposure may be the primary environmental conditions influencing the growth performance of P. penguin. This study therefore recommends that optimal culture sites for P. penguin in Tonga are characterized primarily by warmer water temperatures (25–30°C) and low wave exposure (<15 joules m2 day–1). Culture of P. penguin at sites with more suitable environmental conditions enables pearl production to begin up to 34.2 % (6.5 months) earlier than at less-suitable sites and this may greatly influence mabé pearl farm profitability and feasibility

Incentivizing co-management for impact: mechanisms driving the successful national expansion of Tonga's Special Management Area program

The expansion of coastal marine protected areas can suffer from two key drawbacks: (a) the difficulty of incentivizing local communities to manage areas for conservation when their livelihoods also depend on resource use; and (b) that many protected areas get situated residually, or in locations with limited value for either biodiversity conservation or livelihoods. Here, we discuss and analyze key characteristics of Tonga's Special Management Area (SMA) program, including both the mechanisms that have motivated its successful national expansion and its ability to configure no-take reserves in areas that are considered to have high value to resource users. Granting communities exclusive access zones in exchange for implementing no-take reserves has encouraged conservation actions while fostering long-term relationships with resources. Ensuring no-take reserves occurred within the boundaries of exclusive access zones enabled communities to protect areas of greater extractive values than they would have otherwise. We conclude that the success of this program offers a way forward for achieving targets in the global expansion marine protected areas

Community management yields positive impacts for coastal fisheries resources and biodiversity conservation

Combining no-take marine reserves with exclusive access by communities to unreserved waters could provide the required incentives for community management to achieve positive impacts. However, few protected areas have been critically evaluated for their impact, which involves applying counterfactual thinking to predict conditions within protected areas if management had never occurred. Here, we use statistical matching to conduct a rigorous impact evaluation of dual management systems on coral reef fishes in Tonga, with communities having both full no-take areas and areas of exclusive fishing rights. No-take areas generally had positive impacts on the species richness, biomass, density, and size of target reef fish, while exclusive access areas were similar to predicted counterfactual conditions. The latter is likely because overall fishing pressure in exclusive access areas might not actually change, although more fish could be exploited by communities with access rights. Our findings suggest that dual management is effective at incentivizing effective community-based no-take areas for biodiversity conservation and resource management

Hidden benefits and risks of partial protection for coral reef fisheries

Partially protected areas are now the dominant global form of spatial management aimed at preserving ecosystem integrity and managing human use. However, most evaluations of their efficacy use only a narrow set of conservation indicators that reflect a fraction of ways in which protection can succeed or fail. In this paper, we examine three case studies of partially protected coral reef fishery systems to evaluate benefits and risks of their use as a management tool. We use data from community-based management arrangements in three Pacific Island countries to demonstrate three vignettes of how partial protection can boost fisheries production, enhance the ease with which fishers catch their prey, and alter the composition of fisheries yields. These changes in fisheries productivity, catchability, and vulnerability under partial protection carry substantial benefits for fishers. However, they also carry significant risks for ecosystems and fisheries livelihoods unless adaptively managed so as to confer the short to medium term benefits in resource performance without risking longer term sustainability

Hidden benefits and risks of partial protection for coral reef fisheries

Partially protected areas are now the dominant global form of spatial management aimed at preserving ecosystem integrity and managing human use. However, most evaluations of their efficacy use only a narrow set of conservation indicators that reflect a fraction of ways in which protection can succeed or fail. In this paper, we examine three case studies of partially protected coral reef fishery systems to evaluate benefits and risks of their use as a management tool. We use data from community-based management arrangements in three Pacific Island countries to demonstrate three vignettes of how partial protection can boost fisheries production, enhance the ease with which fishers catch their prey, and alter the composition of fisheries yields. These changes in fisheries productivity, catchability, and vulnerability under partial protection carry substantial benefits for fishers. However, they also carry significant risks for ecosystems and fisheries livelihoods unless adaptively managed so as to confer the short to medium term benefits in resource performance without risking longer term sustainability

Why does conservation minimize opportunity costs?

Effective management of depleted natural resources can be achieved only through changes in human actions. Opportunity costs represent the forgone benefits that would have flowed in the absence of conservation interventions. To the extent that opportunity costs reflect lost opportunities for extractive uses (e.g., fishing or logging), and to the extent that those extractive uses present threats to nature, opportunity costs therefore reflect the positive differences for natural values that can be made through conservation management. Thus, logic dictates that, if conservationists make choices to minimize opportunity costs, they are also necessarily limiting their impact. Unfortunately, empirical evidence from many conservation contexts implies that conservationists indeed make choices consistent with an aim to minimize opportunitycosts, and hence impact. A better understanding of the relationship between opportunity costs and conservation impact will make the language used to communicate conservation progress, targets, and planning more honest and accountable and more explicitly focused on the differences our actions make.</p

Benthic and reef fish surveys from the Kingdom of Tonga in 2016-2018 (375 sites)

This data represents coral reef ecological surveys conducted in the Kingdom of Tonga from 2016-2018. 375 sites were surveyed across the Tongatapu, Ha'apai and Vava'u island groups by Patrick Smallhorn-West, Dr. Daniela Ceccarelli and Karen Stone. Data includes reef fish belt transects and benthic photoquadrats or point intercept data. In addition, the values of a range of socio-environmental predictor variables are also included in this data set. All surveys were conducted on SCUBA. Metadata on depth, location, transect length, width etc. are included in the data files. Socio-environmental spatial data is available at https://doi.pangaea.de/10.1594/PANGAEA.90480