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Abstract: South Africa’s commitment to implementation of the ecosystem approach to fishing (EAF) requires a solid scientific basis comprised of a toolkit assembled through concerted efforts from which management measures can be carefully considered and put into place. A series of workshops was held to assist in the identification of issues in South Africa’s key fisheries that are cause for concern and may have EAF implications. Several of these issues were addressed under various projects. Food-web studies have been undertaken and models have been constructed of the changes in the structure and functioning of the Southern Benguela upwelling system. The combined effects of fishing and environmental change on South African fisheries have been examined using various observation-based and modelling methods. These are contributing to assessment of changes at multiple spatial and temporal scales, from the impact of pelagic fishing in key foraging areas of critically-dependent predators, to impacts of demersal trawls on the benthos and demersal fish assemblages, to decadal-scale dynamics, and global comparative classifications of ecosystem status. To address some of the EAF issues, practical implementation measures are being developed and applied in collaboration with stakeholders. Stakeholders are also actively involved in the process leading to development of indicators to address the human dimensions of EAF, and knowledge-based systems are being developed as decision support tools. Future priorities for South African EAF research will include placing more emphasis on conservation and biodiversity aspects, linking of environmental/oceanographic knowledge to management objectives, spatial aspects, as well as increased focus on the human dimension and transdisciplinary approaches. Indicators are a promising means of synthesizing multi-disciplinary information for consideration in the management process, providing measures of anthropogenic (including fishing) pressures including social and economic pressures, in combination with environmental drivers, and providing a means of assessing how these affect the Benguela ecosystem. Respectful scientific collaboration will be required to bridge the gap between classical single-species fisheries management approaches and broader ecosystem approaches. [Copyright &y& Elsevier]

Shannon, L. J., Coll, M., Yemane, D., Jouffre, D., Neira, S., Bertrand, A., Diaz, E., and Shin, Y-J. 2010. Comparing data-based indicators across upwelling and comparable systems for communicating ecosystem states and trends. – ICES Journal of Marine Science, 67: 807–832.A suite of ecological indicators was selected for communicating, in a comparable way, how fishing affects the state of several upwelling ecosystems and others in which small pelagic fish play key ecological roles. Detailed background and understanding of system-specific processes and changes is needed for proper interpretation of results. In particular, environmental forcing is important in driving dynamics in upwelling systems; fishing impacts cannot be understood without understanding the corresponding dynamics of the environment. The Saharan Coastal (Morocco) and southern Benguela, both having experienced upsurges in low-trophic-level species, differed from other ecosystems when considering indicator trends. The ecosystem off Portugal emerged as showing reduced signs of fishing impacts in recent years, although the change may also be reflecting climate change favouring recruitment and abundance of demersal stocks. The indicator suite confirmed general understanding that the Mediterranean ecosystems have been notably degraded for several decades. Results and conclusions from this descriptive synthesis are compared with other comparisons of more complex, model-derived indicators. Even in upwelling and comparable systems, the simple data-based indicators are useful in synthesizing information on the status of an ecosystem, in particular on the ecosystem effects of fishing, to provide an ecological diagnosis at the ecosystem level, to be used in decision-making. Indicators of recent ecosystem state and trends over time are needed to assess the effects of fishing, but more indicators measuring biodiversity attributes and environmental change would complement the suite, providing fuller assessment of the status of upwelling and comparable ecosystems. [ABSTRACT FROM PUBLISHER]

Bundy, A., Shannon, L. J., Rochet, M-J., Neira, S., Shin, Y-J., Hill, L., and Aydin, K. 2010. The good(ish), the bad, and the ugly: a tripartite classification of ecosystem trends. – ICES Journal of Marine Science, 67: 745–768.Marine ecosystems have been exploited for a long time, growing increasingly vulnerable to collapse and irreversible change. How do we know when an ecosystem may be in danger? A measure of the status of individual stocks is only a partial gauge of its status, and does not include changes at the broader ecosystem level, to non-commercial species or to its structure or functioning. Six ecosystem indicators measuring trends over time were collated for 19 ecosystems, corresponding to four ecological attributes: resource potential, ecosystem structure and functioning, conservation of functional biodiversity, and ecosystem stability and resistance to perturbations. We explored the use of a decision-tree approach, a definition of initial ecosystem state (impacted or non-impacted), and the trends in the ecosystem indicators to classify the ecosystems into improving, stationary, and deteriorating. Ecosystem experts classified all ecosystems as impacted at the time of their initial state. Of these, 15 were diagnosed as “ugly”, because they had deteriorated from an already impacted state. Several also exhibited specific combinations of trends indicating “fishing down the foodweb”, reduction in size structure, reduction in diversity and stability, and changed productivity. The classification provides an initial evaluation for scientists, resource managers, stakeholders, and the general public of the concerning status of ecosystems globally. [ABSTRACT FROM PUBLISHER]

Shin, Y-J., and Shannon, L. J. 2010. Using indicators for evaluating, comparing and communicating the ecological status of exploited marine ecosystems. 1. The IndiSeas project. – ICES Journal of Marine Science, 67: 686–691.One of the challenges faced by the scientific community grappling with the ecosystem approach to fisheries is to propose a generic set of synthetic ecological indicators, which would accurately reflect the effects of fisheries on marine ecosystems, and could support sound communication and management practices. The IndiSeas Working Group was established in 2005 under the auspices of the Eur-Oceans Network of Excellence to develop methods to provide indicators-based assessments of the status of exploited marine ecosystems in a comparative framework. Here, we present the two main outputs of the first phase of the project: a suite of papers documenting a combination of indicator-based methods and results comparing the ecological status of the world's exploited marine ecosystems, and a website aiming to communicate these results beyond scientific audiences. [ABSTRACT FROM PUBLISHER]

Coll, M., Shannon, L. J., Yemane, D., Link, J. S., Ojaveer, H., Neira, S., Jouffre, D., Labrosse, P., Heymans, J. J., Fulton, E. A., and Shin, Y-J. 2010. Ranking the ecological relative status of exploited marine ecosystems. – ICES Journal of Marine Science, 67: 769–786.A set of simple, data-based ecological indicators was used to rank exploited ecosystems regarding fishing impacts with respect to their status, trends, and ecosystem EAF attributes. Expected theoretical changes in indicators with respect to increasing fishing impacts were considered, and ecosystems were compared by examining the mean values of indicators in the most recent three years for which data were available and over time (1980–2005 and 1996–2005). Systems were classified into nine potential categories according to whether they were most, moderately, or least impacted, and whether they were becoming more or less impacted, or remaining stationary. The responses of ecological indicators to additional environmental and socio-economic explanatory factors were tested. Ecosystems ranked using short- and long-term trends and states differed because of differences in trends, underscoring the importance of analysing both states and trends in ecosystem analyses. The number of ecosystems classified as unclear or intermediately impacted has increased recently, the proportion of ecosystems classified as less strongly impacted has been maintained, but more now fall within the category more strongly impacted in terms of long-term trends and states. Ecosystem type, fisheries enforcement, primary production, sea temperature, and fishing type were important variables explaining the ecological indicators. The results reflect different changes and processes in the ecosystems, demonstrating that information on ecological, environmental, and fishery histories is crucial to interpreting indicators correctly, while disentangling the effects of fishing and of the environment. [ABSTRACT FROM PUBLISHER]

Shin, Y-J., Shannon, L. J., Bundy, A., Coll, M., Aydin, K., Bez, N., Blanchard, J. L., Borges, M. F., Diallo, I., Diaz, E., Heymans, J. J., Hill, L., Johannesen, E., Jouffre, D., Kifani, S., Labrosse, P., Link, J. S., Mackinson, S., Masski, H., Möllmann, C., Neira, S., Ojaveer, H., ould Mohammed Abdallahi, K., Perry, I., Thiao, D., Yemane, D., and Cury, P. M. 2010. Using indicators for evaluating, comparing, and communicating the ecological status of exploited marine ecosystems. 2. Setting the scene. – ICES Journal of Marine Science, 67: 692–716.Background is provided to the selection of ecological indicators by the IndiSeas Working Group, and the methodology adopted for analysis and comparison of indicators across exploited marine ecosystems is documented. The selected indicators are presented, how they are calculated is explained, and the philosophy behind the comparative approach is given. The combination of selected indicators is intended to reflect different dynamics, tracking processes that display differential responses to fishing, and is meant to provide a complementary means of assessing marine ecosystem trends and states. IndiSeas relied on inputs and insights provided by the local experts from participating ecosystems, helping to understand state and trend indicators and to disentangle the effect of other potential ecosystem drivers, such as climate variability. This project showed that the use of simple and available indicators under an ecosystem approach can achieve a real, wide-reaching evaluation of marine ecosystem status caused by fishing. This is important because the socio-economics of areas where fishing activities develop differs significantly around the globe, and in many countries, insufficient data are available for complex and exhaustive analyses. [ABSTRACT FROM PUBLISHER]

Abstract: The NW Mediterranean has a number of structural features in common with upwelling ecosystems. Therefore, an ecological model representing a NW Mediterranean exploited ecosystem was standardized and compared with four previously standardized models from coastal upwelling ecosystems: the Northern and Southern Humboldt (Chile and Peru upwelling systems) and the Northern and Southern Benguela (Namibia and South Africa upwelling systems). Results from biomasses, flows and trophic levels indicated important differences between ecosystems, mainly caused by differences in primary production, which was smallest in the NW Mediterranean Sea. However, principal component analysis (PCA) of biomasses and flows suggested a similar pattern between the NW Mediterranean and the South African systems due to the inclusion of an important fraction of the continental shelf in both ecological models representing these areas. At the same time, diets of commercial species from the NW Mediterranean were more similar to Benguela than Humboldt species. However, the relatively heavy fishing pressure in the NW Mediterranean ecosystem was highlighted relative to its primary production, and was evident from the large catches and small primary production, largest flows from TL 1 required to sustain the fishery (%PPR), the low trophic level of the catch (TLc), high exploitation rates (F/Z), largest values in the trophic spectra portraying catch: biomass ratio, the FIB index and the demersal: total catch ration. Comparisons of %PPR, the trophic level of the community (TLco), the biomass of consumers and F/Z ratios seemed to capture the ecosystem effects of fishing: large in the NW Mediterranean, Namibia and Peru upwelling systems. Small pelagic fish were the most important component of the fisheries in the NW Mediterranean and Peruvian systems. However, the smaller production and biomass ratios from the NW Mediterranean could be an indirect indicator of intense fishing pressure on small pelagic fish, also in line with results from consumption of small pelagic fish by the fishery, F/Z ratios and trophic spectra. Moreover, similarities between the NW Mediterranean and Namibian systems were found, mainly related to the demersal: total catch ratios, the FIB index, the relevance of gelatinous zooplankton in the consumption of production and the importance of pelagic-demersal coupling, in remarkable contrast to the other ecosystems. These similarities should be interpreted in terms of dynamic trajectories that the Namibian system has shown due to the collapse of its pelagic ecosystem, partly due to fishing intensity, and the signs that the NW Mediterranean could follow suit in the future. [Copyright &y& Elsevier]

Trophic models of the southern Benguela ecosystem have been developed to represent average ecosystem structures for two periods: 1980–1989 and 1990–1997. Ecopath with Ecosim software is used to simulate changes from the 1980s to the 1990s ecosystem structure. Two hypotheses are tested of mechanisms that could cause the changes. First, using the model of the 1980s, four scenarios are considered in which different combinations of fishing mortality rates of sardine, anchovy and horse mackerel are changed to mimic the situation in the 1990s model. Results show that it is unlikely that observed changes in pelagic fish catches between the 1980s and 1990s played a large role in driving the changes in abundance of anchovy and sardine. Second, changes in the susceptibility of phytoplankton and zooplankton prey to feeding by anchovy and sardine are simulated for the two decades. Results show that shifts between anchovy and sardine regimes in the southern Benguela ecosystem may be caused by changes in the availability of mesozooplankton prey to anchovy and sardine, mediated through changes in environmental conditions. The magnitudes and duration of environmental changes are important in understanding changes in the ecosystem. [Copyright &y& Elsevier]

The northern Benguela ecosystem has been overfished and physically challenged over the past three decades. Ecopath with Ecosim was used to construct three ecosystem models (1971–1977, 1980–1989, and 1990–1995) and to compare differences in ecosystem structure. In the 1970s, the system sustained high catches, and had large populations of a few planktivorous fish. In the 1980s, the planktivorous fish species were expanded (horse mackerel, mesopelagic fish, and other small pelagics), although anchovy and sardine biomass was reduced. Catches remained high in the 1980s and the system was well connected. In the 1990s, the system was severely stressed, catches were much lower and omnivory was reduced. Most of the energy flowed through few pathways in the 1990s, and the energy was not transferred as efficiently up the trophic chain as in the 1980s. The fishery operated at the highest trophic level during the 1980s and there are some indications of “fishing down the foodweb” in this ecosystem between the 1980s and the 1990s. The high catches of sardine and hake in the 1970s are reflected in the high primary production required (PPR) by those compartments; the high catches of horse mackerel in the 1980s are shown by the high PPR for horse mackerel. The overall PPR for the fishery was highest in the 1980s, when the system was fished at nearly the same intensity as the 1970s, but the species taken were from higher trophic levels, requiring larger concentrations of primary production for their own existence. The importance of ecosystem–environmental interactions are highlighted by the abundance of horse mackerel, mesopelagics, small pelagics, and hake in the 1980s and the reduced biomass of most species in the 1990s, not only due to overfishing, but also due to the Benguela Nin˜o that occurred in 1995. The system changed from an efficient ecosystem dominated by only two planktivores (anchovy and sardine) in the 1970s, to a system of large resilience and a varied planktivore population during the 1980s. However, the system’s resilience was lower, but its connectance was higher in the 1990s, where sardine was making a comeback and the marine mammals were doing well until the Benguela Nin˜o reduced the system to a state of lower maturity. [Copyright &y& Elsevier]

Three indicators quantifying interactions between species are developed for an upwelling system to provide useful measures for the comparison of marine ecosystem structure and function. Small pelagic fish are dominant in upwelling systems, and by definition, they are pivotal in a wasp-waist upwelling system. The indicator of interaction strength (IS) quantifies the effect that a change in biomass of one group has on abundance of other groups. The functional impact (FI) indicator quantifies the trophic impacts of species on their own and other functional groups or feeding guilds. The trophic replacement (TR) indicator quantifies the trophic similarity between a species that is removed from an ecosystem and other species in that ecosystem, i.e. it quantifies the ability of one group to trophically replace another. A trophic model of the southern Benguela ecosystem is used as an example for the application of the indicators. The strong similarities in trophic functioning of the southern Benguela ecosystem in the anchovy-dominated system of the 1980s, and the 1990s when there was a shift towards greater sardine abundance, are explained by the mutual trophic replacement abilities of anchovy and sardine. Differences between the proposed indicators and mixed trophic impact assessment are highlighted, mainly resulting from the static versus dynamic nature of the models upon which they are based. Trophic indicators such as those presented here, together with other kinds of ecosystem indicators, may assist in defining operational frameworks for ecosystem-based fisheries management. [Copyright &y& Elsevier]

Mass-balanced models of trophic flows in the southern Benguela ecosystem suggest a 10% increase in zooplankton biomass between the 1980s and the 1990s, in agreement with observed trends of increased zooplankton abundance off South Africa over the last few decades. Minimum hake biomass in balanced trophic models is substantially larger than survey and other model estimates, suggesting undersampling of hakes in surveys and underestimation of juvenile hake mortality. Model biomass and mean annual production of five important small pelagic fish groups were larger in the 1990s, and total catches were smaller than in the 1980s. Estimates of biomass per trophic level, transfer efficiencies, mixed trophic impacts and many other ecosystem attributes suggest that trophic functioning of the southern Benguela ecosystem was similar in the 1980s and 1990s. Because catches were lower and model zooplankton and small pelagic fish biomasses were larger in the 1990s, the ecosystem was less tightly constrained by predators (including fishers) and food availability than in the 1980s. Fishing took place at low trophic levels compared to other systems. Despite smaller total catches in the 1990s, fishing was ecologically more expensive (from higher trophic levels) during the 1990s than in the 1980s because snoek and hake catches were large. There was greater shared niche overlap of small pelagic fish predators in the 1990s than in the 1980s. Mean transfer efficiency was 12%. Transfer of biomass at trophic levels III–V appears to be more efficient in the southern Benguela than in other upwelling ecosystems. Primary production required to sustain catches in the southern Benguela ecosystem is 4% of total primary production, i.e. more similar to estimates for open ocean and coastal regions than for other upwelling or shelf systems averaging more than double this value. [Copyright &y& Elsevier]

Protected and conserved areas (PCAs) are key ecosystem management tools for conserving biodiversity and sustaining ecosystem services and social cobenefits. As countries adopt a 30% target for protection of land and sea under the Global Biodiversity Framework of the United Nations Convention on Biological Diversity, a critical question emerging is, which 30%? A risk‐based answer to this question is that the 30% that returns the greatest reductions in risks of species extinction and ecosystem collapse should be protected. The International Union for Conservation of Nature (IUCN) Red List protocols provide practical methods for assessing these risks. All species, including humans, depend on the integrity of ecosystems for their well‐being and survival. Africa is strategically important for ecosystem management due to convergence of high ecosystem diversity, intense pressures, and high levels of human dependency on nature. We reviewed the outcomes (e.g., applications of ecosystem red‐list assessments to protected‐area design, conservation planning, and management) of a symposium at the inaugural African Protected Areas Congress convened to discuss roles of the IUCN Red List of Ecosystems in the design and management of PCAs. Recent progress was made in ecosystem assessment, with 920 ecosystem types assessed against the IUCN Red List criteria across 21 countries. Although these ecosystems spanned a diversity of environments across the continent, the greatest thematic gaps were for freshwater, marine, and subterranean realms, and large geographic gaps existed in North Africa and parts of West and East Africa. Assessment projects were implemented by a diverse community of government agencies, nongovernmental organizations, and researchers. The assessments have influenced policy and management by informing extensions to and management of formal protected area networks supporting decision‐making for sustainable development, and informing ecosystem conservation and threat abatement within boundaries of PCAs and in surrounding landscapes and seascapes. We recommend further integration of risk assessments in environmental policy and enhanced investment in ecosystem red‐list assessment to fill current gaps. [ABSTRACT FROM AUTHOR]

As one of the most economically important marine ecosystems, the North Sea has been impacted by numerous anthropogenic activities. A move towards an ecosystem approach to fisheries is key in developing sustainable fisheries in marine ecosystems. The application of a previously tested decision tree framework that employs a suite of indicators suggested in the IndiSeas project with additional indicators of environmental variability has been used in this study. Trends in indicators were used to identify ecosystem trends across three periods: 1983-1992, 1993-2003, and 2004-2010. A score-based approach was adopted, assigning scores to indicators based on direction and significance of trends. Ecological indicator scores were adjusted to account for impacts of fishing and environmental variability. Overall ecosystem scores assigned the ecosystem into one of five possible categories: improving, possibly improving, no improvement/deterioration, possibly deteriorating or deteriorating. Results indicated no improvement or deterioration over Period 1 (1983-1992); whereas Periods 2 (1993-2003) and 3 (2004- 2010) showed a possible improvement of the ecosystem. Use of a structured decision tree framework, including extensive literature reviews and knowledge from ecosystem experts, allows the determination of ecosystem trends in a way consistent with ecological theory. [ABSTRACT FROM AUTHOR]

Highlights: [•] We assess changes in the southern Humboldt over the last century using food web models. [•] Fishing is the main predator in the system in the more recent state. [•] The biomass of most target species and top predators decreases in recent models. [•] Groups with small sized individuals having short life spans and at low trophic levels dominate in recent models. [•] The system is more susceptible to external forcing and negative ecological interactions than historically. [Copyright &y& Elsevier]

The effects of climate and fishing on marine ecosystems have usually been studied separately, but their interactions make ecosystem dynamics difficult to understand and predict. Of particular interest to management, the potential synergism or antagonism between fishing pressure and climate forcing is analysed in this paper, using an end-to-end ecosystem model of the southern Benguela ecosystem, built from coupling hydrodynamic, biogeochemical and multispecies fish models (ROMS-N2P2Z2D2-OSMOSE). Scenarios of different intensities of upwelling-favourable wind stress combined with scenarios of fishing top-predator fish were tested. Analyses of isolated drivers show that the bottom-up effect of the climate forcing propagates up the food chain whereas the top-down effect of fishing cascades down to zooplankton in unfavourable environmental conditions but dampens before it reaches phytoplankton. When considering both climate and fishing drivers together, it appears that top-down control dominates the link between top-predator fish and forage fish, whereas interactions between the lower trophic levels are dominated by bottom-up control. The forage fish functional group appears to be a central component of this ecosystem, being the meeting point of two opposite trophic controls. The set of combined scenarios shows that fishing pressure and upwelling-favourable wind stress have mostly dampened effects on fish populations, compared to predictions from the separate effects of the stressors. Dampened effects result in biomass accumulation at the top predator fish level but a depletion of biomass at the forage fish level. This should draw our attention to the evolution of this functional group, which appears as both structurally important in the trophic functioning of the ecosystem, and very sensitive to climate and fishing pressures. In particular, diagnoses considering fishing pressure only might be more optimistic than those that consider combined effects of fishing and environmental variability. [ABSTRACT FROM AUTHOR]

• South African shores were invaded by multiple ecosystem engineers from 1980 to 2015. • Ecosystem engineers changed habitat complexity, which impacts native species. • Layered approach used to model impact of habitat complexity on intertidal ecosystem. • Novel plug-in, EcoEngineer, introduced for Ecospace module of Ecopath with Ecosim. • EcoEngineer showed highest success in modelling invasions by multiple engineers. In a prequel to this paper, we used non-spatial temporal modelling to investigate the impact of non-native ecosystem engineers on a small-scale, intertidal rocky shore in Saldanha Bay, on the west coast of South Africa, where invasive species have changed the physical environment between 1980 and 2015. However, we considered this approach incomplete without the direct inclusion of spatial modelling and zonation. To address this, we compared multiple, layered simulations employing the food-web approach of Ecospace, the spatial-temporal module of Ecopath with Ecosim (EwE). Our simulations included a control; a simulation that restricted drivers to depth and habitat preferences; two simulations to account for structural complexity as a function of the biomass of alien ecosystem engineers – the first indirectly via mediation, and the second via a novel plug-in 'Ecoengineer' – and lastly the inclusion of wave action to replicate its effects. Only the simulation that included the Ecoengineer routine matched empirical observations of species diversity indices and the exclusion of the native mussel Choromytilus meridionalis by the arriving alien Mytilus galloprovincialis. Inclusion of mediation did not differ from the model simulation that used only habitat preference and depth to drive the model, and the addition of wave action did not improve model fits. Our results emphasise that when analysing intertidal ecosystems, they should be modelled with an explicit representation of structural habitat complexity over time and space, and we consider that the application of our Ecoengineer plug-in is an effective and novel way of accomplishing this. [Display omitted] [ABSTRACT FROM AUTHOR]

Link, J. S., Yemane, D., Shannon, L. J., Coll, M., Shin, Y-J., Hill, L., and Borges, M. F. 2010. Relating marine ecosystem indicators to fishing and environmental drivers: an elucidation of contrasting responses. – ICES Journal of Marine Science, 67: 787–795.The usefulness of indicators in detecting ecosystem change depends on three main criteria: the availability of data to estimate the indicator (measurability), the ability to detect change in an ecosystem (sensitivity), and the ability to link the said change in an indicator as a response to a known intervention or pressure (specificity). Here, we specifically examine the third aspect of indicator change, with an emphasis on multiple methods to explore the “relativity” of major ecosystem drivers. We use a suite of multivariate methods to explore the relationships between a pre-established set of fisheries-orientated ecosystem status indicators and the key drivers for those ecosystems (particularly emphasizing proxy indicators for fishing and the environment). The results show the relative importance among fishing and environmental factors, which differed notably across the major types of ecosystems. Yet, they also demonstrated common patterns in which most ecosystems, and indicators of ecosystem dynamics are largely driven by fisheries (landings) or human (human development index) factors, and secondarily by environmental drivers (e.g. AMO, PDO, SST). How one might utilize this empirical evidence in future efforts for ecosystem approaches to fisheries is discussed, highlighting the need to manage fisheries in the context of environmental and other human (e.g. economic) drivers. [ABSTRACT FROM PUBLISHER]

Shin, Y-J., Bundy, A., Shannon, L. J., Simier, M., Coll, M., Fulton, E. A., Link, J. S., Jouffre, D., Ojaveer, H., Mackinson, S., Heymans, J. J., and Raid, T. 2010. Can simple be useful and reliable? Using ecological indicators to represent and compare the states of marine ecosystems. – ICES Journal of Marine Science, 67: 717–731.Within the IndiSeas WG, the evaluation of exploited marine ecosystems has several steps, from simple binary categorization of ecosystems to a more-complex attempt to rank them and to evaluate their status using decision-tree analyses. With the intention of communicating scientific knowledge to the public and stakeholders, focus is on evaluating and comparing the status of exploited marine ecosystems using a set of six ecological indicators and a simple and transparent graphic representation of ecosystem state (pie charts). A question that arose was whether it was acceptable to compare different types of marine ecosystems using a generic set of indicators. To this end, an attempt is made to provide reference levels to which ecosystems can be objectively compared. Unacceptable thresholds for each indicator are determined based on ecological expertise derived from a questionnaire distributed to a group of scientific experts. Analysis of the questionnaires revealed no significant difference in the thresholds provided for different ecosystem types, suggesting that it was reasonable to compare states directly across different types of ecosystem using the set of indicators selected. [ABSTRACT FROM PUBLISHER]

Forage fish populations often undergo large and rapid fluctuations in abundance. However, most of their predators are buffered against such fluctuations owing to their slower pace of life, which allows them to maintain more stable populations, at least during short periods of food scarcity. In this study, we investigated top‐down processes exerted by seabirds on forage fish stocks in five contrasted marine ecosystems, compiling numerous data sets on seabird counts, diets, energetic needs and prey energy content and abundance. Off Norway, South Africa, Peru, Sweden and Scotland, we found that predation pressure—estimated as the proportion of a fish stock consumed by seabirds—was generally low (median = 1%), but increased sharply at low levels of prey abundance. When prey biomass decreased below 15–18% of its maximum recorded value, predation by seabirds became a source of important additional pressure on prey stocks (~20% of prey biomass is consumed by seabirds). An earlier empirical study advocated for keeping forage stocks from falling below a threshold of 33% of long‐term maximum prey biomass in order to safeguard seabird breeding success, but here we further suggest that a threshold of 18% should be considered as a limit not to be exceeded for the sake of the forage fish themselves, and below which extra cautious management of fisheries may be required. Nevertheless, despite exceptionally high rates of predation on some occasions, predation pressure was not correlated with prey dynamics, suggesting an absence of prey entrapment due to seabirds alone in these five ecosystems. [ABSTRACT FROM AUTHOR]

Declining biodiversity and ecosystem functions put many of nature's contributions to people at risk. We review and synthesize the scientific literature to assess 50-y global trends across a broad range of nature's contributions. We distinguish among trends in potential and realized contributions of nature, as well as environmental conditions and the impacts of changes in nature on human quality of life. We find declining trends in the potential for nature to contribute in the majority of material, nonmaterial, and regulating contributions assessed. However, while the realized production of regulating contributions has decreased, realized production of agricultural and many material commodities has increased. Environmental declines negatively affect quality of life, but social adaptation and the availability of substitutes partially offset this decline for some of nature's contributions. Adaptation and substitutes, however, are often imperfect and come at some cost. For many of the contributions of nature, we find differing trends across different countries and regions, income classes, and ethnic and social groups, reinforcing the argument for more consistent and equitable measurement. [ABSTRACT FROM AUTHOR]

• Rare pre- and post-invasion data were used to model rocky-shore ecosystem change. • 22 model simulations explored trophic interactions, non-trophic effects and wave action. • Aliens dominated trophic effects, but adding non-trophic effects improved model fits. • Aliens transformed habitat complexity, but wave-action effects were unexpectedly minor. • Spatial modelling is needed to further increase ecological realism. Between 1980 and 2012, successive arrivals by three alien ecosystem engineers on a rocky shore community at Marcus Island on the west coast of South Africa led to substantial changes in species composition and diversity. An ecosystem analysis of this open intertidal system was developed using Ecopath with Ecosim to determine the impacts of these aliens and the services they provide on the native community. A baseline Ecopath model of the community in 2015 was generated using values of biomass, production/biomass, consumption/biomass and the dietary composition of 30 functional groups. Ecosim, a time-dynamic modelling routine, was then used to simulate the changes in biomass of native species. A 1980 model (pre-invasion) was constructed and 22 simulations were run up to 2015 by systematically adding (1) biomass time series for non-native species; (2) relative biomass time series for native species; (3) mediation functions that mimicked biomass impacts due to changes in substrate, shelter and feeding grounds created by the alien ecosystem engineers; and (4) the effects of wave action as a source of mortality. Positive or negative influences of these ecological processes on diversity and the final biomasses of all groups in 2015 were assessed. Trophic impacts by the alien species affected diversity and biomass at the end of all simulations, but the addition of shelter or a combination of all three ecosystem services provided by ecosystem engineers (shelter, substrate and feeding grounds) resulted in 2015 model ecosystems that most closely matched the diversity and individual group biomasses empirically measured on Marcus Island in 2015. Wave action had only a minor impact. Marcus Island's rocky shore community was therefore driven mainly by the fixed input of alien species biomass and made more realistic by the incorporation of their ecosystem services. However, structural complexity and zonation, explored in a follow-up paper invoking spatial modelling, need to be represented for a more complete realisation of the ecosystem. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Assessing risks to marine ecosystems is critical due to their biological and economic importance, and because many have recently undergone regime shifts due to overfishing and environmental change. Yet defining collapsed ecosystem states, selecting informative indicators and reconstructing long-term marine ecosystem changes remains challenging. The IUCN Red List of Ecosystems constitutes the global standard for quantifying risks to ecosystems and we conducted the first Red List assessment of an offshore marine ecosystem, focusing on the southern Benguela in South Africa. We used an analogous but collapsed ecosystem – the northern Benguela – to help define collapse in the southern Benguela and derived collapse thresholds with structured expert elicitation (i.e. repeatable estimation by expert judgment). To capture complex ecosystem dynamics and reconstruct historical ecosystem states, we used environmental indicators as well as survey-, catch- and model-based indicators. We listed the ecosystem in 1960 and 2015 as Endangered, with assessment outcomes robust to alternative model parametrizations. While many indicators improved between 1960 and 2015, seabird populations have suffered large declines since 1900 and remain at risk, pointing towards ongoing management priorities. Catch-based indicators often over-estimated risks compared to survey- and model-based indicators, warning against listing ecosystems as threatened solely based on indicators of pressure. We show that risk assessments provide a framework for interpreting data from indicators, ecosystem models and experts to inform the management of marine ecosystems. This work highlights the feasibility of conducting Red List of Ecosystems assessments for marine ecosystems. Highlights • We applied the IUCN Red List of Ecosystems criteria to an offshore marine ecosystem. • We list the southern Benguela as Endangered in 1960 and 2015. • Risk assessments synthesize information from multiple data sources and timeframes. • Many indicators have recently improved, but seabirds have suffered declines since 1900. • Catch-based indicators are not recommended for marine ecosystem Red Listing. [ABSTRACT FROM AUTHOR]

There is an increasing need to understand ecosystem responses to multiple stressors in that such complex responses depend not only on species-level responses, but also on species interactions and ecosystem structure. In this study, we used a multi-model ecosystem simulation approach to explore the combined effects of fishing and primary productivity on different components of the food-web across a suite of ecosystems and a range of model types. Simulations were carried out under different levels of primary productivity and various fishing scenarios. In addition to exploring synergistic, additive or antagonistic combined effects of multiple stressors, we included a fourth category “dampened”, which refers to less negative or less positive impacts compared to additive ones, and in contrast to previous studies, we explicitly considered the direction (positive or negative) of the combined effects. We focused on two specific combined effects (negative synergism and positive dampened) associated with the risk of resultant lower fish biomass than expected under additive effects. Through a meta-analysis of the multi-models' simulation results, we found that (i) the risk of negative synergism was generally higher for low-trophic-level (LTL) taxa, implying that following an increase of fishing pressure on a given LTL stock, the subsequent decrease of biomass under low primary productivity would be larger than expected under additive effects and (ii) the risk of positive dampened effects was generally higher for high-trophic-level (HTL) taxa, implying that given a management measure aimed at reducing the impact of fishing on HTL stocks, the subsequent rebuilding of these stocks would be slower than expected. Our approach to categorizing and exploring cumulative effects can be applied to evaluate other community properties, and provide guidance for fisheries management. [ABSTRACT FROM AUTHOR]

Several commercially and ecologically important species in the southern Benguela have undergone southward and eastward shifts in their distributions over previous decades, most notably the small pelagic fish sardine Sardinops sagax and anchovy Engraulis encrasicolus. Understanding these changes and their implications is essential in implementing an ecosystem approach to fisheries in the southern Benguela and attempting to appreciate the potential impacts of future environmental change. To investigate possible impacts of these shifts at an ecosystem level, distribution maps for before (1985–1991), during (1997–2000) and after (2003–2008) the shift in small pelagic fish were constructed for 14 key species from catch and survey data, and used to calculate spatial indicators including proportion east and west of Cape Agulhas, relative overlap in biomass and area, index of diversity, connectivity. Potential interactions on the south and west coasts were also compared. For several species (redeye; chub mackerel; kingklip; chokka squid; yellowtail), previously unidentified increases in the proportion of biomass east of Cape Agulhas were shown to have occurred over the same period as that of small pelagic fish, although none to the same degree. On average, overlap with small pelagic fish increased over time and overall system connectivity was lowest in the intermediate period, possibly indicating a system under transition. Connectivity declined over time on the west coast while increasing on the east coast. Distributions of other species have changed over time, with the region east of Cape Agulhas becoming increasingly important in terms of potential trophic interaction. Variations in distribution of biomass and structural complexity affect the trophic structure and hence functioning of the system, and implications should be considered when attempting to identify the possible ecosystem impacts of current and future system-level change. [ABSTRACT FROM AUTHOR]

African penguins ( Spheniscus demersus ) in South Africa have been subject to rapid decline in the 20th century and are currently listed as “endangered” on the IUCN Red List. A stochastic, stage-specific system dynamics model with spatial components was developed to investigate the interaction of multiple pressures on penguin population development, and originally applied to study conservation management options for the penguin colony at Robben Island, Table Bay, South Africa. We here present an extension of the model to the nearby colony at Dyer Island. The modelled population was found to be strongly dominated by the effects of Cape fur seal ( Arctocephalus pusillus pusillus ) predation and immature emigration, which appear to be key drivers behind current declines in population numbers at this colony. Chronic low-level oiling also had a consistent impact despite ongoing mitigation measures, while kelp gull predation had a lower effect than expected. At current low population size, the pressure from either seal predation or immature emigration seems sufficient to mask any beneficial effects to penguins from possible improvements in available food biomass (e.g., from fishery restrictions). Results suggest that conservation management at this colony should focus on regular culling of predating seals combined with improving availability of prey (thus discouraging emigration) both in the foraging range of breeding penguins and in their general foraging area. Our findings demonstrate the use of site-specific scenario tools to explore conservation strategies in data-poor management situations. [ABSTRACT FROM AUTHOR]

Understanding how external pressures impact ecosystem structure and functioning is essential for ecosystem-based approaches to fisheries management. We quantified the relative effects of fisheries exploitation and environmental conditions on ecological indicators derived from two different data sources, fisheries catch data (catch-based) and fisheries independent survey data (survey-based) for 12 marine ecosystems using a partial least squares path modeling approach (PLS-PM). We linked these ecological indicators to the total biomass of the ecosystem. Although the effects of exploitation and environmental conditions differed across the ecosystems, some general results can be drawn from the comparative approach. Interestingly, the PLS-PM analyses showed that survey-based indicators were less tightly associated with each other than the catch-based ones. The analyses also showed that the effects of environmental conditions on the ecological indicators were predominantly significant, and tended to be negative, suggesting that in the recent period, indicators accounted for changes in environmental conditions and the changes were more likely to be adverse. Total biomass was associated with fisheries exploitation and environmental conditions; however its association with the ecological indicators was weak across the ecosystems. Knowledge of the relative influence of exploitation and environmental pressures on the dynamics within exploited ecosystems will help us to move towards ecosystem-based approaches to fisheries management. PLS-PM proved to be a useful approach to quantify the relative effects of fisheries exploitation and environmental conditions and suggest it could be used more widely in fisheries oceanography. [ABSTRACT FROM AUTHOR]

Changes in two contrasting ecosystems of the Benguela upwelling region, one dominated at mid-trophic level by jellyfishes (Namibia, northern Benguela ecosystem, where small pelagic fish abundance has been severely depleted) and one still dominated by small pelagic fishes (South Africa, southern Benguela) were compared in an effort to determine ecosystem trajectories under different exploitation regimes. The role of small pelagic fishes (clupeoids) was highlighted in the context of their importance in maintaining interactions in marine ecosystems. In particular, we examined trophic cascades and possible irreversible changes that promote the proliferation of jellyfishes in marine systems. We found that the presence of large populations of small pelagic fishes has a fundamental role in preserving beneficial trophic interactions in these marine ecosystems. The implications of trophic cascades, such as those observed in the northern Benguela, for ecosystem-based management were apparent. In addition, this comparison provides contrasting case studies to inform the development of management scenarios that avoid ecosystem shifts that affect predators and reduce the value of fisheries production. [ABSTRACT FROM AUTHOR]

Low--trophic level species account for more than 30% of global fisheries production and contribute substantially to global food security. We used a range of ecosystem models to explore the effects of fishing low--trophic level species on marine ecosystems, including marine mammals and seabirds, and on other commercially important species. In five well-studied ecosystems, we found that fishing these species at conventional maximum sustainable yield (MSY) levels can have large impacts on other parts of the ecosystem, particularly when they constitute a high proportion of the biomass in the ecosystem or are highly connected in the food web. Halving exploitation rates would result in much lower impacts on marine ecosystems while still achieving 80% of MSY. [ABSTRACT FROM AUTHOR]

Abstract: From 1989 to 2004, the breeding success of African penguins Spheniscus demersus at Robben Island, South Africa was significantly related to estimates of the abundance of both their main prey species, anchovy Engraulis encrasicolus and sardine Sardinops sagax, and to the combined biomass of these species. When the combined spawner biomass of fish prey was less than 2millionton, pairs fledged an average of 0.46 chicks annually. When it was above 2millionton, annual breeding success had a mean value of 0.73 chicks per pair. Given previously estimated values of survival and age at first breeding, these levels of breeding success are inadequate to sustain the African penguin population. With the higher level of breeding success, an equilibrium situation might be attained if adult survival could be increased by 6–7% per annum. Attempts to reduce mortality of penguins have included the collection, cleaning and return to the wild of oiled birds, culling of Cape fur seals Arctocephalus pusillus pusillus seen preying on penguins around breeding localities and control of the spread of disease. Management of the purse-seine fishery should ensure adequate escapement of fish to maintain the combined biomass of anchovy and sardine above 2millionton. The maintenance of suitable breeding habitat and removal of feral predators from breeding localities will also be important in improving breeding success. [Copyright &y& Elsevier]

Maintenance of overall ecosystem complexity is perceived as critical to the sustainability of ecosystem use. The development of an operational basis for an ecosystem approach to fisheries, however, faces many difficulties. On the research side, the challenge is in defining proper long-term, ecosystem-related objectives; determining meaningful reference values and indicators for desirable or undesirable states of the ecosystem; and developing appropriate data collection, analytical tools and models. The “viability” concept developed in economics by Jean-Pierre Aubin can be used to assist in the definition, selection of, and interaction among long-term objectives at an ecosystem level. It recognizes that ecosystems are complex assemblages of interacting and self-organizing natural and human components that cannot be predicted. Viability models define an ensemble of “viable states”, in contrast to undesirable states defined as such by ecological, economic, and/or social constraints. These constraints can be derived from fisheries objectives, conservation principles, scientific results of modelling, or precautionary principles, and correspond to limit reference points to be avoided. Viability theory does not attempt to choose any “optimal solution” according to given criteria, but selects “viable evolutions”. These evolutions are compatible with the constraints in the sense that they satisfy them at each time and can be delineated by the viability kernel. The southern Benguela marine ecosystem is presented as a first attempt for the application of this theory. In defining ecosystem-based objectives (and related issues such as target reference points), it seems more difficult to reach consensus among stakeholders on what is desirable than on what is undesirable (e.g. biological or economic collapse, species extinction, displacement of local rural communities). Expressed in the negative form or as limit reference points, ecosystem-based constraints can be considered simultaneously with current target reference points, such as maximum sustainable yield, using viability models. The viability approach can help to progressively integrate ecosystem considerations, such as conservation, into fisheries management. [Copyright &y& Elsevier]

Based on published distribution maps of 15 key fish species, foraging areas of three top predators during their breeding season, and fishing grounds of the main commercial fleets in the southern Benguela ecosystem, seven spatialized ecosystem indicators are derived: biodiversity, connectivity, mean ratio of fished area and area of distribution by species, exploited fraction of the ecosystem surface area, total catch per fished area by fishery, mean bottom depth of catches, and mean distance of catches from the coast. These indicators are compared and their suitability for an ecosystem approach to fisheries is discussed. The first two indicators characterize the ecosystem; the others are pressure indicators that are also compared with conventional (catch rate) indices of abundance. [Copyright &y& Elsevier]

Large-scale, mass-balance trophic models have been developed for northern and southern regions of both the Benguela and Humboldt upwelling ecosystems. Four of these Ecopath models were compared and calibrated against one another. A common model structure was established, and a common basis was used to derive poorly known parameter values. The four resulting models represent ecosystems in which the main commercial fish species have been moderately to heavily fished: central-southern Chile (1992), northern-central Peru (1973–1981), South Africa (1980–1989), and Namibia (1995–2000). Quantitative ecosystem indicators derived from these models were compared. Indicators based on large flows (involving low trophic levels) or top predators were not well estimated, because of aggregation problems. Many of the indicators could be contrasted on the basis of differences between the Benguela and Humboldt systems, rather than on the basis of fishing impact. These include integrated values relating to total catches, and trophic levels of key species groups. Indicators based on integrated biomass, total production, and total consumption tended to capture differences between the model for Namibia (where fish populations were severely reduced) and the other models. We conclude that a suite of indicators is required to represent ecosystem state, and that interpretation requires relatively detailed understanding of the different ecosystems. [Copyright &y& Elsevier]