Estimating the rate of exchange of individuals among populations is a central concern to evolutionary ecology and its applications to conservation and management. For instance, the efficiency of protected areas in sustaining locally endangered populations and ecosystems depends on reserve network connectivity. The population genetics theory offers a powerful framework for estimating dispersal distances and migration rates from molecular data. In the marine realm, however, decades of molecular studies have met limited success in inferring genetic connectivity, due to the frequent lack of spatial genetic structure in species exhibiting high fecundity and dispersal capabilities. This is especially true within biogeographic regions bounded by well-known hotspots of genetic differentiation. Here, we provide an overview of the current methods for estimating genetic connectivity using molecular markers and propose several directions for improving existing approaches using large population genomic datasets. We highlight several issues that limit the effectiveness of methods based on neutral markers when there is virtually no genetic differentiation among samples. We then focus on alternative methods based on markers influenced by selection. Although some of these methodologies are still underexplored, our aim was to stimulate new research to test how broadly they are applicable to nonmodel marine species. We argue that the increased ability to apply the concepts of cline analyses will improve dispersal inferences across physical and ecological barriers that reduce connectivity locally. We finally present how neutral markers hitchhiking with selected loci can also provide information about connectivity patterns within apparently well-mixed biogeographic regions. We contend that one of the most promising applications of population genomics is the use of outlier loci to delineate relevant conservation units and related eco-geographic features across which connectivity can be measured.
Multinational conservation initiatives that prioritize investment across a region invariably navigate trade-offs among multiple objectives. It seems logical to focus where several objectives can be achieved efficiently, but such multi-objective hotspots may be ecologically inappropriate, or politically inequitable. Here we devise a framework to facilitate a regionally cohesive set of marine-protected areas driven by national preferences and supported by quantitative conservation prioritization analyses, and illustrate it using the Coral Triangle Initiative. We identify areas important for achieving six objectives to address ecosystem representation, threatened fauna, connectivity and climate change. We expose trade-offs between areas that contribute substantially to several objectives and those meeting one or two objectives extremely well. Hence there are two strategies to guide countries choosing to implement regional goals nationally: multi-objective hotspots and complementary sets of single-objective priorities. This novel framework is applicable to any multilateral or global initiative seeking to apply quantitative information in decision making.
Mangroves provide multiple ecosystem services such as blue carbon sequestration, storm protection, and unique habitat for species. Despite these services, mangroves are being lost at rapid rates around the world. Using the best available biophysical and socio-economic data, we present the first rigorous large-scale evaluation of the effectiveness of protected areas (PAs) at conserving mangroves and reducing blue carbon emissions. We focus on Indonesia as it has the largest absolute area of mangroves (about 22.6% of the world's mangroves), is one of the most diverse in terms of mangrove species and has been losing its mangroves at a very fast rate. Specifically, we apply quasi-experimental techniques (combining propensity score and covariate matching, differences-in-differences, and post-matching bias adjustments) to assess whether PAs prevented mangrove loss between 2000 and 2010. Our results show that marine protected areas reduced mangrove loss by about 14,000 ha and avoided blue carbon emissions of approximately 13 million metric tons (CO2 equivalent). However, we find no evidence that species management PAs stalled the loss of mangroves. We conclude by providing illustrative estimates of the blue carbon benefits of establishing PAs, which can be cost-effective policies for mitigating climate change and biodiversity loss.
- Improving resource information alone has limited effect on decision-making processes.
- A formal participatory MSE allows for more transparency in the management process.
- It supports strategy design, communication and shared understanding about management issues.
- Participatory methods can help modify individual attitudes and group interactions.
Marine legislation is becoming more complex and marine ecosystem-based management is specified in national and regional legislative frameworks. Shelf-seas community and ecosystem models (hereafter termed ecosystem models) are central to the delivery of ecosystem-based management, but there is limited uptake and use of model products by decision makers in Europe and the UK in comparison with other countries. In this study, the challenges to the uptake and use of ecosystem models in support of marine environmental management are assessed using the UK capability as an example. The UK has a broad capability in marine ecosystem modelling, with at least 14 different models that support management, but few examples exist of ecosystem modelling that underpin policy or management decisions. To improve understanding of policy and management issues that can be addressed using ecosystem models, a workshop was convened that brought together advisors, assessors, biologists, social scientists, economists, modellers, statisticians, policy makers, and funders. Some policy requirements were identified that can be addressed without further model development including: attribution of environmental change to underlying drivers, integration of models and observations to develop more efficient monitoring programmes, assessment of indicator performance for different management goals, and the costs and benefit of legislation. Multi-model ensembles are being developed in cases where many models exist, but model structures are very diverse making a standardised approach of combining outputs a significant challenge, and there is a need for new methodologies for describing, analysing, and visualising uncertainties. A stronger link to social and economic systems is needed to increase the range of policy-related questions that can be addressed. It is also important to improve communication between policy and modelling communities so that there is a shared understanding of the strengths and limitations of ecosystem models.
In the Baltic Sea, the pikeperch is one of the commercially important coastal fish species. Most of the local pikeperch stocks in this area can be classified as data-limited. There is an increasing need to monitor the state of all commercial fish stocks in European waters due to the EU Marine Strategy Framework Directive (MSFD). Proper stock assessment is not required in all cases, and alternative and less data demanding approaches and indicators can also be applied. In this study, we combined data on three of the best-studied coastal pikeperch stocks in the northern Baltic Sea to evaluate the performance of length at maturity indicators. A connection was found between intensive selective fishing and the length at maturity (TL50) of female pikeperch. Power analysis indicated that a sample size of 200–400 females, or around 35–70 samples per year, produces reasonable and almost maximal precision when determining the six-year mean TL50 for a stock. Our analysis also demonstrated that in cases where a monitored parameter is annually variable, an increase in the annual sample size does not continuously yield higher precision in the long-term mean, but it is crucial that samples are collected annually. We conclude that TL50 is a promising and cost-efficient indicator of the effects of fisheries on the maturation of coastal pikeperch stocks. This indicator could be further tested after a few years when more data become available.
In the Arctic region global environmental change creates economic opportunities for various sectors, which is increasing pressure on marine biological resources. Next to state governance arrangements, informational governance instruments deployed by non-state actors, such as private certification schemes, mapping exercises and observation systems, play a progressive role in introducing ecosystem-based approaches for governing the marine environment. In this paper we review recent academic literature to understand the role of environmental information in Arctic marine governance. Our review reveals that environmental information may on one hand enable safe or sustainable operations of actors by creating legitimacy and building trust, while on the other hand the participation and empowerment of some actors may constrain other actors, leading to conflict and controversy. We conclude that the growing importance of environmental information in Arctic marine governance is driven both by state management systems and non-state actors, that currently the enabling role of information dominates the literature, but that the constraining role of information will likely increase in future Arctic marine governance.
Grey reef sharks (Carcharhinus amblyrhynchos) can be one of the numerically dominant high order predators on pristine coral reefs, yet their numbers have declined even in the highly regulated Australian Great Barrier Reef (GBR) Marine Park. Knowledge of both large scale and fine scale genetic connectivity of grey reef sharks is essential for their effective management, but no genetic data are yet available. We investigated grey reef shark genetic structure in the GBR across a 1200 km latitudinal gradient, comparing empirical data with models simulating different levels of migration. The empirical data did not reveal any genetic structuring along the entire latitudinal gradient sampled, suggesting regular widespread dispersal and gene flow of the species throughout most of the GBR. Our simulated datasets indicate that even with substantial migrations (up to 25% of individuals migrating between neighboring reefs) both large scale genetic structure and genotypic spatial autocorrelation at the reef scale were maintained. We suggest that present migration rates therefore exceed this level. These findings have important implications regarding the effectiveness of networks of spatially discontinuous Marine Protected Areas to protect reef sharks.
There is an urgent need to develop simple indicators of fishing effects for the implementation of ecosystem-based fisheries management in the Caribbean. In this study, we compare the ability of three simple metrics (average individual fish weight, fish density, and fish biomass) derived from the parrotfish assemblage and from an assemblage of highly valued commercial fish species to track changes in fishing pressure at spatial scales relevant to small Caribbean islands. Between June and August 2011, we conducted five consecutive visual fish surveys at six reefs ≤10 km apart along the west coast of Barbados, representing a spatial gradient in fishing pressure. We used these data to identify the fish metrics most strongly correlated with fishing pressure and describe their functional relationship with fishing pressure. Overall, average individual parrotfish weight and biomass and density of commercial fish species were the metrics most strongly correlated with fishing pressure, although for the latter two, such correlations depended on the range of fish body sizes analyzed. Fishing pressure accounted for most of the variability in all correlated fish metrics (adj R 2 ≥ 0.75). However, functional relationships with fishing pressure differed qualitatively between metrics. In particular, average individual parrotfish weight was the metric most sensitive to incremental changes in fishing pressure. Overall, our study highlights that assemblage-level average individual parrotfish weight deserves a place in the toolbox of Caribbean reef managers as a simple indicator of both fishing effects on parrotfish assemblages and overall fishing pressure on the reef fish community.
Incorporating the perspectives and insights of stakeholders is an essential component of ecosystem-based fisheries management, such that policy strategies should account for the diverse interests of various groups of anglers to enhance their efficacy. Here we assessed fishing stakeholders’ perceptions on the management of Atlantic striped bass (Morone saxatilis) and receptiveness to potential future regulations using an online survey of recreational and commercial fishers in Massachusetts and Connecticut (USA). Our results indicate that most fishers harbored adequate to positive perceptions of current striped bass management policies when asked to grade their state’s management regime. Yet, subtle differences in perceptions existed between recreational and commercial fishers, as well as across individuals with differing levels of fishing experience, resource dependency, and tournament participation. Recreational fishers in both states were generally supportive or neutral towards potential management actions including slot limits (71%) and mandated circle hooks to reduce mortality of released fish (74%), but less supportive of reduced recreational bag limits (51%). Although commercial anglers were typically less supportive of management changes than their recreational counterparts, the majority were still supportive of slot limits (54%) and mandated use of circle hooks (56%). Our study suggests that both recreational and commercial fishers are generally supportive of additional management strategies aimed at sustaining healthy striped bass populations and agree on a variety of strategies. However, both stakeholder groups were less supportive of harvest reductions, which is the most direct measure of reducing mortality available to fisheries managers. By revealing factors that influence stakeholders’ support or willingness to comply with management strategies, studies such as ours can help managers identify potential stakeholder support for or conflicts that may result from regulation changes.