Sylvie Guénette

Marine Reserves: from Beverton and Holt to the Present

The idea of using marine reserves, where all fishing is banned is not new to fisheries management. It was first formally considered by Beverton and Holt but rejected in favour of approaches such as fleet and gear control. Since that analysis, many fisheries have collapsed worldwide, illustrating the vulnerability of fishery resources and the ineffectiveness of these approaches. Empirical data and modelling suggest that marine reserves would generally increase yields, especially at the high fishing mortality that occurs in most fisheries. However, the most interesting feature of reserves is their ability to provide resilience to overexploitation, thereby reducing the risk of stock collapse. Benefits from reserves come from the increase in biomass and individual size within them, resulting in adult migration and/or larval dispersal that would replenish fishing grounds. The use of marine reserves in managing fisheries necessitates a thorough understanding of critical habitat requirements, fish movement, fish behaviour, the relations between subpopulations and the critical density effect for larval dispersal. When properly designed, and coupled with other management practices, reserves may provide a better insurance against uncertainties in stock assessment, fishing control and management by protecting a part of the population from exploitation. This strategy can be used for both sedentary and migratory species.

An age-structured model showing the benefits of marine reserves in controlling overexploitation

Abstract Previous modelling of areas closed to fishing (marine reserves) has generally employed non-dynamic models and has not included biological factors such as stock–recruitment and weight–fecundity relations. These models predicted that a marine reserve would result in a decrease in fishery yield, an increase in spawning biomass and that movements of fish across the reserve boundaries could reduce its benefits. We utilised an age-structured model based on an Atlantic cod population that included more realistic reproductive factors. We compared a Reserve regime that contained a reserve with a No-reserve regime in which the usual fishery management tools were used. As exploitation rate increased, the relative recruitment and spawners biomass decreased in the No-reserve regime. Larger reserves resulted in more robust recruitment and biomass of spawners. At low exploitation rates, marine reserves resulted in smaller yields. However, when the exploitation rate was larger than the rate which gives the maximum sustainable yield, the biomass of female spawners was maintained at a higher level in the Reserve regime and hence the yield did not collapse. Faster rate of movement of fish decreased these advantages, but the higher spawners biomass and level of recruitment still provided advantages for the Reserve regime. Moreover, even for highly mobile fish, our model suggests that a fish stock protected with a marine reserve would be more resilient to exploitation than when managed without. However, a model realistic spatially and temporally would be necessary to assess the usefulness of marine reserves to prevent overexploitation of migrating fish.

Fisheries Impacts on North Atlantic Ecosystems : Models and Analyses

The biological communities of the Atlantic continental shelf adjacent to the southeastern United States are well known, but this knowledge is not integrated into a cohesive description of that region. We constructed a preliminary food web model of this area using Ecopath with Ecosim, as a way to initiate a long-term process of integrating this knowledge, learning more about the structure and resiliency of the system, and helping to guide research priorities in the future. The current model is considered to be a first iteration that can be used as a vehicle to stimulate a more rigorous refinement effort in the near future. The ecologically defined area covered by this model extends from Cape Hatteras, North Carolina to the easternmost extent of the Florida Keys, and from the intertidal zone (or the entrance of estuarine systems) to the 500 m isobath. The time period characterized by this preliminary model is the four years from 1995 to 1998.

Lessons from Marine Protected Areas and Integrated Ocean Management Initiatives in Canada

There is a wave of interest in Marine Protected Areas (MPA) and Integrated Management (IM) as tools for addressing declines in marine environments through ecosystem-based management. Lessons learned from seven MPA and two IM initiatives in Canada show how engaging stakeholders results in: building and maintaining momentum through social capital; using the collective knowledge of stakeholders; consensus through formal and informal rules; and developing leadership capacity. However, as the number of issues or the number of stakeholders increases—especially where fisheries are involved—time, resources, and challenges in gaining support and participation increase. Political and administrative obstacles and resistance to change still constitute much of the challenge. Finally, funding and political commitment must be allocated from the start; otherwise momentum stops and it is hard to regain even when funding becomes available.

Evaluating Network Analysis Indicators of Ecosystem Status in the Gulf of Alaska

This is the first study on the emergent properties for empirical ecosystem models that have been validated by time series information. Ecosystem models of the western and central Aleutian Islands and Southeast Alaska were used to examine indices of ecosystem status generated from network analysis and incorporated into Ecopath with Ecosim. Dynamic simulations of the two ecosystems over the past 40 years were employed to examine if these indices reflect the dissimilar changes that occurred in the ecosystems. The results showed that the total systems throughput (TST) and ascendancy (A) followed the climate change signature (Pacific decadal oscillation, PDO) in both ecosystems, whereas the redundancy (R) followed the inverse trend. The different trajectories for important species such as Steller sea lions (Eumetopias jubatus), Atka mackerel (Pleurogrammus monopterygius), pollock (Theragra chalcograma), herring (Clupea pallasii), Pacific cod (Gadus macrocephalus) and halibut (Hippoglossus stenolepis) were noticeable in the Finn cycling index (FCI), entropy (H) and average mutual information (AMI): not showing large change during the time that the Stellers sea lions, herring, Pacific cod, halibut and arrowtooth flounder (Atheresthes stomias) increased in Southeast Alaska, but showing large declines during the decline of Steller sea lions, sharks, Atka mackerel and arrowtooth flounder in the Aleutians. On the whole, there was a change in the emergent properties of the Aleutians around 1976 that was not seen in Southeast Alaska. Conversely, the emergent properties of both systems showed a change around 1988, which indicated that both systems were unstable after 1988.

Decline of demersal resources in North-West Africa: an analysis of Mauritanian trawl-survey data over the past 25 years

Mauritania is characterised by fast-growing fisheries that have developed over the past decades. Since 1982, scientific trawl surveys have been conducted regularly, allowing assessment of the impact of this increasing fishing pressure on exploited species as well as on demersal communities. Based on 55 bottom trawl surveys and using linear model techniques, the annual abundances were estimated for a selection of 24 fish stocks and for the whole demersal biomass. Changes in the demersal community structure were also investigated, using Biomass Trophic Spectra representations. It is shown that the demersal biomass has been reduced by 75% on the Mauritanian continental shelf over the past 25 years, corresponding to a biomass loss of around 20 000t per year. Top predators abundance has been reduced by 8–10-fold and in some case up to 20-fold. The trophic structure has been significantly modified and the mean trophic level of the catchable biomass decreased from >3.7 to <3.5. The results are discussed at the regional scale, taking into account recent studies in Senegal and Guinea in which a similar decline in demersal biomass was observed. This decline was due to severe overexploitation that affected the various groups in succession.

Assessing the Contribution of Marine Protected Areas to the Trophic Functioning of Ecosystems: A Model for the Banc d’Arguin and the Mauritanian Shelf

Most modelling studies addressed the effectiveness of marine protected areas (MPA) for fisheries sustainability through single species approach. Only a few models analysed the potential benefits of MPAs at the ecosystem level, estimating the potential export of fish biomass from the reserve or analysing the trophic relationships between organisms inside and outside the MPA. Here, we propose to use food web models to assess the contribution of a MPA to the trophic functioning of a larger ecosystem. This approach is applied to the Banc d’Arguin National Park, a large MPA located on the Mauritanian shelf. The ecosystem was modeled using Ecopath with Ecosim, a model that accounts for fisheries, food web structure, and some aspects of the spatial distribution of species, for the period 1991–2006. Gaps in knowledge and uncertainty were taken into account by building three different models. Results showed that the Banc d’Arguin contributes about 9 to 13% to the total consumption, is supporting about 23% of the total production and 18% of the total catch of the Mauritanian shelf ecosystem, and up to 50% for coastal fish. Of the 29 exploited groups, 15 depend on the Banc for more than 30% of their direct or indirect consumptions. Between 1991 and 2006, the fishing pressure increased leading to a decrease in biomass and the catch of high trophic levels, confirming their overall overexploitation. Ecosim simulations showed that adding a new fleet in the Banc d’Arguin would have large impacts on the species with a high reliance on the Banc for food, resulting in a 23% decrease in the current outside MPA catches. We conclude on the usefulness of food web models to assess MPAs contribution to larger ecosystem functioning.

Ecosystem-based global fishing policy scenarios

The future of fisheries and marine ecosystems at the global scale, until recently, was often expressed in terms of qualitative storylines with limited quantitative information on how aspects of fisheries such as landings, profits and biodiversity would respond, which constrained the comparing of outcomes across geographic areas. However, the construction of a stratified global model, EcoOcean, has met many of the challenges of quantitatively assessing the future of fisheries under different scenarios. Using the Ecopath with Ecosim (EwE) software, a series of 19 marine ecosystem models representing the 19 FAO areas of the world’s oceans and seas was constructed. The models were populated using global datasets of catches, ex-vessel prices, biomass and distant water fleets from the Sea Around Us Project and the fleet statistics from the Food and Agriculture Organization of the United Nations (FAO). The fleet statistics were used to develop a global database of fishing effort for the five fishing fleets in the model from 1950 to 1998, the last year for which the data are available. Modelling the five fisheries over the 19 FAO areas from 1950 to 2003 resulted in an aggregated global total that was within 10% of the reported total for any given year. This gave some confidence that the models are providing plausible results for different scenarios, in particular for the four scenarios of the Global Environment Outlook 4 and the four scenarios of the International Assessment for Agricultural Science, Technology and Development. This work also provided the opportunity to look at the future of marine biodiversity to 2048, using a depletion index as a proxy for changes in species composition and abundance under the different scenarios. This report presents the background and development of EcoOcean, the model structure, a detailed description of the effort reconstruction, and the underlying datasets that are used to construct and drive the models, especially prices and jobs. The report also discusses the implications of EcoOcean as a policy tool and how it can be further refined to be of wider use and to reduce the uncertainty of the modelled outputs. The application of EcoOcean to GEO4 and the IAASTD resulted in plausible outcomes under the different policy scenarios, and the outcomes differed across geographic areas as well as across scenarios. Some policy scenarios called for increasing landings or profits, rebuilding ecosystems, or a combination of all three with and without subsidies. In cases where effort increased, landings and therefore profits increased; however, any increase in landings was achieved by increases in groups that are not currently fished in large quantities. In many cases increased landings resulted in declining marine trophic levels, and increased depletion risks. a Cite as: Alder, J., Guénette, S., Beblow, J., Cheung, W. and Christensen, V. 2007. Ecosystem-based global fishing policy scenarios. Fisheries Centre Research Reports 15(7). Fisheries Centre, University of British Columbia [ISSN 1198-6727]. Ecosystem-Based Global Fishing Policy Scenarios, Alder, Guénette, Beblow, Cheung and Christensen 4 INTRODUCTION Recent ecological studies including the recent IPCC2 have focused the world’s attention on the need to consider how future policy can be shaped to address environmental issues. Policy makers have a number of tools at their disposal to make well-reasoned policies that will effect change in the world’s ecosystems, while addressing other issues affecting humankind, especially poverty and economic development as articulated in the Millennium Development Goals (Anonymous, 2007). The global crisis in marine fisheries is included in the suite of issues to be addressed, because the world’s fisheries contributes to food security, as well as assistance in the economic development for many countries, especially so for developing coastal countries (Pauly et al., 2005). One tool that is gaining recognition for this purpose is scenario analysis. It was first used in strategic planning during the cold war (Khan and Weiner, 1967) and was key to the Shell Oil Company coping with the oil crisis of the 1970s (Wack, 1985a, 1985b). Its use assisting in policy formulation in natural resources management and sustainable development sectors, especially at the global scale, emerged in the 1970s (Raskin et al., 2005). There was little development of scenario analysis until late in the 1980s, when concerns over climate change and sustainable development took off. A number of climate change scenarios were thus developed in the 1990s with the IPCC (Raskin, 2000) providing a framework for the further development of scenarios analyses. Development of scenarios within the IPCC area has shaped much of how scenarios are used, reported and evaluated in other studies including the Millennium Ecosystem Assessment, GEO43, IAASTD4, OECD5 and GLOBIO Project6. The development of the global model EcoOcean, which we report on here, was a response to a growing demand for analyses of how, especially fisheries, may impact the future of marine systems for policy making at regional and global scales. In particular, there was a demand for a global oceans model for the United Nations’ Global Environment Outlook 4 (GEO4) and IAASTD as inputs into future scenarios under different policy options. Scenarios as used here can be defined as “plausible, challenging and relevant stories about how the future might unfold which can be told in both words and numbers. They are not forecasts, projections, predictions or recommendations. They are about envisioning future pathways and accounting for critical uncertainties”(Raskin et al., 2005). In this context the EcoOcean model was developed as a tool to explore fisheries and more broadly, marine policy options and not to predict the future. As Peterson et al.(2003) note, predictive modelling works for simulating well-understood systems over the short-term, but as complexity and the modelling time frame increase, predictive power declines. In such systems, the system state is well specified and mathematical algorithms are available to describe relationships used in the quantitative predictions (Raskin, 2005). Much progress has been made in describing such relationships through ecosystem modelling (Christensen and Walters, 2005) and a natural progression has been to bring these models into the field of scenario analysis. While ecosystem modelling has been used extensively for research purposes, it is only now beginning to be used as part of the fisheries policy process, and has yet to be used for large marine regions. As fishery policy moves beyond the objectives for single-species management there is indeed no choice but to adopt more elaborate ecosystem models. Policy choices for ecosystembased fisheries management involve exploring the impact of non-traditional policy choices and our abilities to perform such explorations are severely limited. In the past, we have based comparisons of ecosystem-related policy choices on methods ranging from very simple risk avoidance models, to simple food chain or trophic cascade models, to very complex food web 2 IPCC = Intergovernmental Panel on Climate Change 3 GEO4 = United Nations’ Global Environment Outlook 4 (UNEP 2007) 4 IAASTD = International Assessment for Agricultural Science Technology and Development (Fernandez in press) 5 OECD = Organization for Economic Co-operation and Development 6 GLOBIO = Global Methodology for Mapping Human Impacts on the Biosphere (see www.globio.info) Ecosystem-Based Global Fishing Policy Scenarios, Alder, Guénette, Beblow, Cheung and Christensen 5 models that attempt to explore possible reverberating effects going beyond direct predator-prey interactions. Much of the recent ecosystem modelling work has been aimed mainly at assessing risks of the more complex reverberating effects such as ‘cultivation-depensation’ effects (Walters and Kitchell, 2001), on the assumption that complex interactions are likely to result in counterintuitive responses (Yodzis, 2001) Based on the Ecopath with Ecosim (EwE) approach and software, we developed a new model, EcoOcean, to explore scenarios for the world’s oceans. Christensen and Walters (2004) give a detailed discussion of EwE. The model was constructed using 43 functional groups that are common to the world’s oceans including FAO’s 19 marine statistical areas. The groups were selected with special consideration for exploited fish species, but are intended to jointly include all major groups in the oceans. The fish groups are based on size categories, and feeding and habitat characteristics. Fishing effort is the most important driver for the ecosystem model simulations. The 19 FAO areas were considered large enough to encompass the range of most marine fish and invertebrates as well as accommodating the world’s major fishing fleets. Five major fleet categories, i.e., demersal, distant-water fleet, baitfish tuna (purse seine), tuna longline and small pelagic are used to distinguish different fishing effort based on historical information. This model structure allows for maximum flexibility in meeting different global assessment objectives, while still providing a valid representation of the marine systems. Background Scenario analyses can have quantitative modelling and qualitative narrative components; providing systematic and replicable representations as well as contrasting social visions and descriptions (Raskin et al., 2005). The process of developing scenarios itself often expands people’s perspectives and identifies key issues that might have been missed or dismissed at the initial stages of planning or assessment. Qualitative components help to describe values, behaviours and institutions, while quantitative components provide structure and rigour (Raskin et al., 2005). A review of previous scenarios over the last three decades illustrates the benefits and limits of using models and

A trophic model of the coral reef ecosystem of La Parguera, Puerto Rico: synthesizing fisheries and ecological data

Abstract. La Parguera, Puerto Rico, a well-studied Caribbean reef system, is showing signs of overfishing and thus, is a good candidate to evaluate fishery policy scenarios using ecosystem modeling. The first steps taken to build a plausible ecosystem model of the La Parguera reef system using Ecopath with Ecosim software included synthesizing fisheries and ecological data then balancing and analyzing trophic relationships for the year 2000. The model is centered around species of commercial and ecological importance in the ecosystem, grouped by habitat preferences. Model construction identified gaps in available data (e.g., diet compositions, metrics of fishing effort, incomplete landings) and balancing raised interesting ecological questions. Some groups, such as parrotfish are so underutilized as prey that the accuracy of biomass estimates and our understanding of predator-prey relationships are questioned. Apparent shortcomings in estimates of primary production relative to consumer biomass generated questions of whether estimates are inaccurate or whether the system is highly subsidized by importation from outside ecosystem boundaries. Although details are not directly comparable because of different structures, a similar Carribean model built for the 1970–1980s estimated total biomass 5.6 times higher than the present model. Changes of this magnitude, if found to be accurate, point out the need for further study of the roles fishing and environmental change have played in reshaping this system over the last 30–40 years. This modeling effort defined future data needs, generated hypotheses for further coral reef research, and provided a starting point towards evaluation of fishery management scenarios in an ecosystem context.