Publications

The science of spatial fisheries management, which combines ecology, oceanography, and economics, has matured significantly. As a result, there have been recent advances in exploiting spatially explicit data to develop spatially explicit management policies, such as networks of marine protected areas (MPAs). However, when data are sparse, spatially explicit policies become less viable, and we must instead rely on blunt policies such as total allowable catches or imprecisely configured networks of MPAs. Therefore, spatial information has the potential to change management approaches and thus has value. We develop a general framework within which to analyze the value of information for spatial fisheries management and apply that framework to several US Pacific coast fisheries. We find that improved spatial information can increase fishery value significantly (>10% in our simulations), and that it changes dramatically the efficient management approach—switching from diffuse effort everywhere to a strategy where fishing is spatially targeted, with some areas under intensive harvest and others closed to fishing. Using all available information, even when incomplete, is essential to management success and may as much as double fishery value relative to using (admittedly incorrect) assumptions commonly invoked.

Fishing has clear direct effects on harvested species, but its cascading, indirect effects are less well understood. Fishing disproportionately removes larger, predatory fishes from marine food webs. Most studies of the consequent indirect effects focus on density‐mediated interactions where predator removal alternately drives increases and decreases in abundances of successively lower trophic‐level species. While prey may increase in number with fewer predators, they may also alter their behavior. When such behavioral responses impact the food resources of prey species, behaviorally mediated trophic cascades can dramatically shape landscapes. It remains unclear whether this pathway of change is typically triggered by ocean fishing. By coupling a simple foraging model with empirical observations from coral reefs, we provide a mechanistic basis for understanding and predicting how predator harvest can alter the landscape of risk for herbivores and consequently drive dramatic changes in primary producer distributions. These results broaden trophic cascade predictions for fisheries to include behavioral changes. They also provide a framework for detecting the presence and magnitude of behaviorally mediated cascades. This knowledge will help to reconcile the disparity between expected and observed patterns of fishing‐induced cascades in the sea.

Marine protected areas (MPAs) and spatial property rights (TURFs) are two seemingly contradictory approaches advocated as solutions to common property failures in fisheries. MPAs limit harvest to certain areas, but may enhance profits outside via spillover. TURFs incentivize local stewardship but may be plagued by spatial externalities when the TURF size is insufficient to capture all dispersal. Within a numerical model parameterized to a California marine species, we explore the economic and ecological effects of imposing MPAs on a TURF-regulated fishery. Whether MPAs can enhance or diminish profits (or fish abundance) hinges critically on the level of coordination already occurring between TURF owners. If coordination is complete, private MPAs may already emerge in some TURFs; implementing additional MPAs reduces profits. However, to the extent that coordination is incomplete, strategically sited MPAs may be an effective complement to spatial property rights-based fisheries, increasing both fishery profits and abundance.

A common strategy for limiting the total annual catch in a fishery is to restrict entry and season length. We examine the results of this strategy when entry limitation amounts to a limit on capital, but fishing firms can vary an unrestricted input, and thereby use the restricted input more intensively. Under these regulatory constraints, fishing firms will earn rents that depend on the elasticity of substitution between restricted and unrestricted inputs. Using simulations with data from the Alaskan pollock fishery, rents and season length are shown to depend on fish and variable input prices, sometimes in surprisingly non-monotonic ways.

Widespread global collapses of fisheries corroborate decades-old predictions by economists, made long before large-scale industrialization of the world's fisheries, that open access would have deleterious ecological and economic effects on fishery resources. Incentive-based alternatives (collectively called catch shares) have been shown to generate pecuniary benefits, but little empirical evidence exists for, or against, a link to global fisheries sustainability. We report and expand on an analysis of >11,000 fisheries worldwide, in which we investigated the causes of fisheries collapse from 1950 to 2003. Using a program evaluation design, we found that catch shares prevent and, in some specifications, reverse fisheries collapse. Subsequent scientific studies reinforce and challenge these findings, suggesting fruitful avenues for future research linking incentive-based resource management to sustainability.

Every fishery is embedded in a matrix of political institutions, and these institutions, together with other factors, determine the management regime that will best capture the resource’s potential rent. This chapter examines evidence on this link. Resource management structures are equivalent to property rights regimes because they delineate who has authority to decide how a resource is used and to determine how the resource’s returns are distributed among various parties. For this reason the following discussion links political conditions to the performance of specific assignments of property rights, with the focus on fisheries.

Trophic cascades triggered by fishing have profound implications for marine ecosystems and the socioeconomic systems that depend on them. With the number of reported cases quickly growing, key features and commonalities have emerged. Fishery-induced trophic cascades often display differential response times and nonlinear trajectories among trophic levels and can be accompanied by shifts in alternative states. Furthermore, their magnitude appears to be context dependent, varying as a function of species diversity, regional oceanography, local physical disturbance, habitat complexity, and the nature of the fishery itself. To conserve and manage exploited marine ecosystems, there is a pressing need for an improved understanding of the conditions that promote or inhibit the cascading consequences of fishing. Future research should investigate how the trophic effects of fishing interact with other human disturbances, identify strongly interacting species and ecosystem features that confer resilience to exploitation, determine ranges of predator depletion that elicit trophic cascades, pinpoint antecedents that signal ecosystem state shifts, and quantify variation in trophic rates across oceanographic conditions. This information will advance predictive models designed to forecast the trophic effects of fishing and will allow managers to better anticipate and avoid fishery-induced trophic cascades.

Management and conservation can be greatly informed by considering explicitly how environmental factors influence population genetic structure. Using simulated larval dispersal estimates based on ocean current observations, we demonstrate how explicit consideration of frequency of exchange of larvae among sites via ocean advection can fundamentally change the interpretation of empirical population genetic structuring as compared with conventional spatial genetic analyses. Both frequency of larval exchange and empirical genetic difference were uncorrelated with Euclidean distance between sites. When transformed into relative oceanographic distances and integrated into a genetic isolation-by-distance framework, however, the frequency of larval exchange explained nearly 50 per cent of the variance in empirical genetic differences among sites over scales of tens of kilometres. Explanatory power was strongest when we considered effects of multiple generations of larval dispersal via intermediary locations on the long-term probability of exchange between sites. Our results uncover meaningful spatial patterning to population genetic structuring that corresponds with ocean circulation. This study advances our ability to interpret population structure from complex genetic data characteristic of high gene flow species, validates recent advances in oceanographic approaches for assessing larval dispersal and represents a novel approach to characterize population connectivity at small spatial scales germane to conservation and fisheries management.

Declining ocean health, increasing human demands on marine ecosystems, and a history of management focused on individual activities, species or sectors has led to calls for more comprehensive, integrated management that considers entire coupled social-ecological systems. This transition to ecosystem-based management (EBM) for the oceans will certainly face a number of hurdles, and many practitioners struggle with how to move forward with EBM. In this paper, we assess whether the necessary science exists to support EBM. Specifically, we evaluate the state of the social and natural sciences for three research areas that are critical to EBM: (1) ecosystem services, (2) cumulative impacts, and (3) ecosystem variability and change. For each of the three research areas, we describe its importance to EBM and assess existing and emerging information and application of this knowledge, focusing on the US West Coast. We conclude that available science is not the bottleneck for moving forward with comprehensive EBM for this region, although we highlight important remaining knowledge gaps, particularly within the social sciences. Given imperfect and uncertain knowledge, EBM calls for an adaptive management approach, starting with readily available information, and continuously adapting as new information emerges. This synthesis can serve as a basis for comparison for other regions; it provides guidance for organizing information in support of EBM and outlines many novel and broadly applicable scientific approaches.

Widespread concern exists over the health of marine ecosystems given the diversity and impact of human activities affecting these systems worldwide (Halpern et al. 2008), with overfishing consistently identified as a key threat to all parts of the world's oceans (Pauly et al. 1998). Overexploitation has resulted in dire predictions about the ability of oceans to continue supporting fisheries (Worm et al. 2006), in turn leading to calls for fishery management reform (Costello et al. 2008) and increased protection to maintain some locations in a more 'pristine' ecosystem state (Lubchenco et al. 2003). No-take marine reserves, which prohibit all exploitative activities, have become widely recognized as an effective conservation tool for protecting marine resources, resulting in increases in the abundance, biomass and diversity of many species within their boundaries (Halpern 2003; Micheli et al. 2004; Lester et al. 2009). However, the ability for reserves to provide conservation or fisheries benefits to adjacent waters remains highly controversial (Roberts et al. 2001; Tupper 2002; Gell & Roberts 2003; Hilborn et al. 2004).

Marine reserves may not only protect populations within their borders but also subsidize harvested populations outside through the spillover of either adults or planktonic larvae. The conservation benefits of marine reserves are well documented, and a growing body of evidence suggests that the spillover of large adults from reserves can enhance fisheries for highly mobile species. However, the proposed benefit to fisheries through larval export, a crucial benefit for the many marine species without highly mobile adults, remains controversial. We tested for larval export by estimating larval production and recruitment patterns of a harvested intertidal mussel, Perna perna, inside - and a range of distances outside - 3 marine reserves in South Africa. Within the borders of 2 reserves, mussels were more abundant and larger than outside the reserves, with significantly higher expected production. Recruitment was highest inside these reserves and declined exponentially with distance. In the third region, where harvest outside reserve boundaries is carefully managed by community members, no differences in production or recruitment inside versus outside the reserve were found. Where production and recruitment were enhanced, we used the inverse relationship of recruitment with distance from the reserves to determine the spatial scale and magnitude of larval export. Our results suggest that larval export from these reserves enhances recruitment to fished areas within several kilometers. This study supports the idea that increased production in reserves may subsidize fisheries outside their borders, even for species with immobile adults. ©nter-Research 2009.

After a long history of overexploitation, increasing efforts to restore marine ecosystems and rebuild fisheries are under way. Here, we analyze current trends from a fisheries and conservation perspective. In 5 of 10 well-studied ecosystems, the average exploitation rate has recently declined and is now at or below the rate predicted to achieve maximum sustainable yield for seven systems. Yet 63% of assessed fish stocks worldwide still require rebuilding, and even lower exploitation rates are needed to reverse the collapse of vulnerable species. Combined fisheries and conservation objectives can be achieved by merging diverse management actions, including catch restrictions, gear modification, and closed areas, depending on local context. Impacts of international fleets and the lack of alternatives to fishing complicate prospects for rebuilding fisheries in many poorer regions, highlighting the need for a global perspective on rebuilding marine resources.

The study and implementation of no-take marine reserves have increased rapidly over the past decade, providing ample data on the biological effects of reserve protection for a wide range of geographic locations and organisms. The plethora of new studies affords the opportunity to reevaluate previous findings and address formerly unanswered questions with extensive data syntheses. Our results show, on average, positive effects of reserve protection on the biomass, numerical density, species richness, and size of organisms within their boundaries which are remarkably similar to those of past syntheses despite a near doubling of data. New analyses indicate that (1) these results do not appear to be an artifact of reserves being sited in better locations; (2) results do not appear to be driven by displaced fishing effort outside of reserves; (3) contrary to often-made assertions, reserves have similar if not greater positive effects in temperate settings, at least for reef ecosystems; (4) even small reserves can produce significant biological responses irrespective of latitude, although more data are needed to test whether reserve effects scale with reserve size; and (5) effects of reserves vary for different taxonomic groups and for taxa with various characteristics, and not all species increase in response to reserve protection. There is considerable variation in the responses documented across all the reserves in our data set — variability which cannot be entirely explained by which species were studied. We suggest that reserve characteristics and context, particularly the intensity of fishing outside the reserve and inside the reserve before implementation, play key roles in determining the direction and magnitude of the reserve response. However, despite considerable variability, positive responses are far more common than no differences or negative responses, validating the potential for well designed and enforced reserves to serve as globally important conservation and management tools.

Predictions on the efficacy of marine reserves for benefiting fisheries differ in large part due to considerations of models of either intra- or inter-cohort population density regulating fish recruitment. Here, I consider both processes acting on recruitment and show using a bioeconomic model how for many fisheries density dependent recruitment dynamics interact with harvest costs to influence fishery profit with reserves. Reserves consolidate fishing effort, favoring fisheries that can profitably harvest low-density stocks of species where adult density mediates recruitment. Conversely, proportion coastline in reserves that maximizes profit, and relative improvement in profit from reserves over conventional management, decline with increasing harvest costs and the relative importance of intra-cohort density dependence. Reserves never increase profit when harvest cost is high, regardless of density dependent recruitment dynamics. I quantitatively synthesize diverse results in the literature, show disproportionate effects on the economic performance of reserves from considering only inter- or intra-cohort density dependence, and highlight fish population and fishery dynamics predicted to be complementary to reserve management.

The Experimental Program to Stimulate Competitive Research (EPSCoR) was designed to help U.S. states with limited facilities improve their research infrastructure in order to make them more competitive for nationwide grants, such as the R01. Twenty-seven states and territories (including Puerto Rico and the U.S. Virgin Islands) have been designated EPSCoR states (1). In a recent Letter (“Declines in NIH R01 research grant funding,” 10 October 2008, p. 189), H. G. Mandel and E. S. Vesell presented the current funding statistics for R01 grants. These findings and other changes in policy (2) demonstrate the difficulty in getting R01 grants funded in the current climate. The existing funding situation encourages investigators from EPSCoR states to take their R01 grants and leave for better institutions because better institutions have the resources to obtain new R01 grants and renew R01 grants.

How can institutions in EPSCoR states retain their scientists with R01 grants under these difficult conditions? It may be necessary to offer extremely competitive financial packages to scientists from elsewhere with R01s or to change the promotion and tenure policies; perhaps scientists who have R01s could receive early promotion and tenure, or the tenure clock could be extended to give scientists more time to obtain an R01.

Recent reports suggest that most of the world's commercial fisheries could collapse within decades. Although poor fisheries governance is often implicated, evaluation of solutions remains rare. Bioeconomic theory and case studies suggest that rights-based catch shares can provide individual incentives for sustainable harvest that is less prone to collapse. To test whether catch-share fishery reforms achieve these hypothetical benefits, we have compiled a global database of fisheries institutions and catch statistics in 11,135 fisheries from 1950 to 2003. Implementation of catch shares halts, and even reverses, the global trend toward widespread collapse. Institutional change has the potential for greatly altering the future of global fisheries.

Many nearshore fish and invertebrate populations are overexploited even when apparently coherent management structures are in place. One potential cause of mismanagement may be a poor understanding and accounting of stochasticity, particularly for stock recruitment. Many of the fishes and invertebrates that comprise nearshore fisheries are relatively sedentary as adults but have an obligate larval pelagic stage that is dispersed by ocean currents. Here, we demonstrate that larval connectivity is inherently an intermittent and heterogeneous process on annual time scales. This stochasticity arises from the advection of pelagic larvae by chaotic coastal circulations. This result departs from typical assumptions where larvae simply diffuse from one site to another or where complex connectivity patterns are created by transport within spatially complicated environments. We derive a statistical model for the expected variability in larval settlement patterns and demonstrate how larval connectivity varies as a function of different biological and physical processes. The stochastic nature of larval connectivity creates an unavoidable uncertainty in the assessment of fish recruitment and the resulting forecasts of sustainable yields.

David Festa, Diane Regas, and Judson Boomhower's compelling account "Sharing the Catch, Conserving the Fish" ( Issues , Winter 2008) echoes mounting theoretical and empirical evidence on the powerful ability of economic incentives to provide resource users with strong motivation for good stewardship. The question for policymakers should no longer be if or when to implement these innovations, but how to design them to achieve biological, economic, and social objectives.
Most current fisheries management approaches generate two inherent conflicts: between a fisherman's short- and long-term interests and between the short-term incentives of a fisherman and the longer-term public good. These conflicts exist because there are strong incentives for fishermen to overfish and spend too much money doing it. These mismatches can be reversed with appropriate design of secure-access programs that align short- and long-term interests. Providing fishermen with economic incentives to conserve is smart
management. 

We characterize the optimal harvest of a renewable resource in a generalized stochastic spatially explicit model. Despite the complexity of the model, we are able to obtain sharp analytical results. We find that the optimal harvest rule in general depends upon dispersal patterns of the resource across space, and only in special circumstances do we find a modified golden rule of growth that is independent of dispersal patterns. We also find that the optimal harvest rule may include closure of some areas to harvest, either on a temporary or permanent basis (biological reserves). Reserves alone cannot correct open access, but may, under sufficient spatial heterogeneity and connectivity, increase profits if appropriate harvest controls are in place outside of reserves.

Spillover of fish from marine reserves to adjacent harvested waters may be mediated by density-independent movement, density-dependent movement, or both. If dispersal is by random movement, populations within the reserve must be regulated by density-dependent population growth (DDG). Density-dependent movement (DDM) can also regulate the population if accelerated emigration from a reserve to the surrounding fishing grounds leads to substantially increased mortality. Using spatially explicit models, we show that stock per unit area is bounded for DDG and increases with size for DDM. With DDG, spillover rate per unit area of reserve is maximized with reserves around 50% larger in linear dimension than the minimum size for population persistence. With DDM, spillover per unit area of reserve increases with reserve size. The results highlight the need for the mechanism of population regulation to be incorporated into theoretical and empirical investigations of marine reserve ecology.