- The relative availability of alternative organic matter sources directly influences trophic interactions within ecological communities. As differences in trophic ecology can alter the productivity of communities, understanding spatial variability in trophic structure, and the drivers of variability, is vital for implementing effective ecosystem‐based management.
- Bulk stable isotope analysis (δ13C and δ15N) and mass balance calculations were used to examine patterns in the contribution of organic matter derived from macroalgae to food webs supporting temperate reef fish communities in two contrasting coastal waterways on the South Island of New Zealand: Fiordland and the Marlborough Sounds. Ten fish species common to both regions were compared, with up to 40% less organic matter from macroalgae supporting omnivorous species in the Marlborough Sounds. The largest differences in trophic position were found in those species exploited by fisheries.
- Furthermore, stratified surveys of abundance and species biomass combined with trophic position data were used to calculate regional differences in the contribution of macroalgae to whole fish communities in terms of density of biomass. In Fiordland, over 77% of the biomass of exploited reef fishes was supported by macroalgae, compared with 31% in the Marlborough Sounds.
- Surveys of macroalgal density and species composition in the two regions indicated that regional differences in trophodynamics may be explained by a lack of macroalgal inputs to the food web in the Marlborough Sounds.
- The findings demonstrate large regional differences in the incorporation of benthic and pelagic sources of organic matter to food webs supporting reef fish communities, highlighting the need for ecosystem‐based approaches to management to recognize spatial variability in primary production supporting coastal food webs.
Ecosystem-based Management (EBM)
The need for management approaches based on ecosystem perspectives that thoroughly incorporate ecosystem considerations into marine planning has become increasingly urgent. In response, concepts such as ecosystem-based management (EBM), ecosystem-based approach (EBA) and ecosystem approach (EA) are increasingly being applied in marine/maritime spatial planning (MSP). The purpose of this article is to clarify potential differences and similarities between the three concepts and potential consequences of choosing one over the others. From a questionnaire and literature analysis, the findings showed vast disagreements on how the concepts are related, however the main perception is that the concepts overlap. Respondents agreed that a lack of clear definitions and understandings of the three concepts causes confusion and expect negative consequences for planning outcomes. Eleven principles for how the concepts are ideally performed were found, including; acknowledge interlinkages, see humans as a part of the ecosystem and consider cumulative impacts. While a complete overlap between EBM and EA principles were found, the weighting of each principle was different for each concept. Differences were also found in objectives of the concepts, where definitions of EBM were the only ones to include the objective of co-existence and definitions of EBA the only to include objectives of impact management and good environmental status. As this could have consequences in planning processes and thus in the outcomes, it is crucial that MSP practitioners and stakeholders are aware of different perceptions so that choosing between concepts does not lead to less ambitious or inadequate outcomes.
Primary considerations for adopting an ecosystem approach to fisheries management (EAFM) as a management approach will involve an expanded scope of fisheries management over conventional approaches; specifically, EAFM will involve a broader scale of management. Development of a sub-regional EAFM plan can complement local, national, and regional fisheries management priorities, as well as help to catalyze management action at multiple levels that may not otherwise occur. A sub-regional EAFM policy planning approach has been undertaken for the Sulu-Sulawesi Seascape (SSS), a sub-region of Southeast Asia. This sub-regional policy planning approach illustrates how “scaling up” EAFM can support relevant international, regional, and other sub-regional fisheries management plans and environmental initiatives, while “scaling down” EAF can support relevant national, provincial/state, and local fisheries management plans in Indonesia, Malaysia and the Philippines.
There is growing empirical evidence around the world demonstrating regime shifts of marine ecosystems. But generalizable criteria to detect and define regime shifts are elusive because of: (i) an incomplete scientific understanding of processes underlying regime shifts; (ii) because the baseline state and conditions are ill defined, and; (iii) due to an inherent ambiguity in the concept of system identity. We surveyed marine scientists in Tasmania, Australia, and determined the effect of changing conditions (including type of climate impact, species loss, species composition, spatio-temporal extent, and human intervention) on their perception of marine regime shift. We find, there is an objective difficulty in detecting regime shifts that goes beyond scientific uncertainty and there is disagreement on which configurations of change indeed constitute a regime shift. Furthermore, this difference of opinion was not related to the degree of confidence that scientists indicated when identifying regime shifts. This lack of consensus and seemingly unrelated scientific confidence, may be attributable to value ambiguity around people s attitudes, cognitive biases, and baseline shift. When applying evidenced-based reference points in well-reasoned Ecosystem Based Management, there should be scientific consensus on the manifestation and extent of specific regime shifts, and recognition of value ambiguities influencing scientific perceptions.
Change is inherent in coastal systems, which are amongst the most dynamic ones on Earth. Increasing anthropogenic pressure on coastal zones interferes with natural coastal dynamics and can cause ecosystem imbalances that render the zones less stable. Furthermore, human occupation of coastal zones often requires an uncharacteristic degree of stability for these inherently dynamic coastal systems. Coastal management teams face multifaceted challenges in protecting, rehabilitating and conserving coastal systems. Diverse monitoring schemes and modelling tools have been developed to address these challenges. In this article, we explore various perspectives: the integration of biophysical, ecological and social components; the uncertainties of diverse data sources; and the development of flexible coastal interventions. We propose general criteria and guidance for an Ecosystem-based Management (EbM) to coastal management, which aims primarily at adaptation to global change and uncertainties, and to managing and integrating social aspects and biophysical components based on the flows of energy and matter.
In 2017, South Africa became the first African country to draft Marine Spatial Planning (MSP) legislation. The underlying legal framework supports the achievement of ecological, social and economic objectives, but a national policy to fast track the oceans economy provides a challenge for ecosystem-based approaches to MSP. During the 2018 International Marine Conservation Congress, we convened a session to present particular challenges that will likely apply to any developing country seeking to increase profits from existing, or proposed, marine activities. Here we present six multi-disciplinary research projects that support ecosystem-based approaches to MSP in South Africa, by addressing the following knowledge gaps and specific key challenges: (1) the lack of data-derived measurements of ecosystem condition (and the need to validate commonly-used proxy measures); (2) the need to develop models to better understand the potential impacts of climate change on food webs and fisheries; (3) the slow implementation of an ecosystem approach to fisheries management, and the need to implement existing legal instruments that can support such an approach; (4) the paucity of evidence supporting dynamic ocean management strategies; (5) the requirement to manage conflicting objectives in growing marine tourism industries; and (6) the need to adopt systems thinking approaches to support integrated ocean management. We provide examples of specific research projects designed to address these challenges. The ultimate goal of this research is to advance a more integrated approach to ocean management in South Africa, using tools that can be applied in countries with similar socio-political and environmental contexts.
There are several emergent properties useful as indicators of marine ecosystem status. Some of these are based on the cumulative trophic theory, which posits that biomass and production accumulate in repeatable and predictable patterns across trophic levels. These patterns result in a suite of curve parameters that can delineate when a marine ecosystem is undergoing perturbation or recovery. When looking at this suite of curve parameters, and their trajectories over time, a clear sense of perturbation, recovery, or transition can be delineated. From a set of over 3700 observations we established empirical threshold levels for the curve parameters, i.e., Trophic Level inflection point, Biomass inflection point and Steepness at 3.38 ± 0.05, 0.33 ± 0.01 and 0.50 ± 0.56, respectively. When the three parameters are examined collectively to determine whether a particular ecosystem datum was below or above each of these three thresholds, clear three-dimensional patterns emerged. First, some volumes in this 3-D space of parameters simply did not have data, and many volumes had very little. The majority of data (approximately 40%) occurred in situations with Steepness and Biomass inflection point higher than thresholds. Almost none of the ecosystems (<1%) was below all three thresholds at any point in time, a quarter of the data resulted in critical conditions for at least a couple of indicators, a little less than half of the ecosystems (52%) at any point in time seem to be quite functional from this emergent property perspective, and finally, a moderate number of ecosystems, at any point in time (22%), seem to be in some type of transition state. We assert that these emergent properties have value for delineating ecosystem state, and at the very least when the Biomass inflection point is <33% an ecosystem is understood to have been severely degraded. Using these three thresholds, and identifying whether data trajectories are crossing them or not, has strong potential to better indicate the status of marine ecosystems, trajectories thereof, and hence when management interventions are needed.
Global aquatic biodiversity keeps declining rapidly, despite international efforts providing a variety of policies and legislations that identify goals for, and give directions to protecting the world's aquatic fauna and flora. With the H2020 project AQUACROSS, we have made an unprecedented effort to unify policy strategies, knowledge, and management concepts of freshwater, coastal, and marine ecosystems to support the achievement of the targets set by the EU Biodiversity Strategy to 2020. AQUACROSS has embraced the concept of ecosystem-based management (EBM), which approaches environmental management from a social-ecological system perspective to protect biodiversity and to sustainably harvest ecosystem services. This special issue includes contributions resulting from AQUACROSS, which either tackle selected EBM challenges from a theoretical point of view or apply EBM in one of the selected case studies across Europe. In this article, we introduce relevant topics, address the most important lessons learnt, and suggest where research should go with aquatic EBM. We hope that this special issue will foster and facilitate the uptake of EBM in aquatic ecosystems and, therewith, provide the on-ground applications needed for evaluating EBM's utility to safeguard aquatic biodiversity.
Climate-driven changes in ocean currents have facilitated the range extension of the long-spined sea urchin (Centrostephanus rodgersii) from Australia’s mainland to eastern Tasmania over recent decades. Since its arrival, destructive grazing by the urchin has led to widespread formation of sea urchin ‘barrens’. The loss of habitat, biodiversity and productivity for important commercial reef species in conjunction with the development of an urchin fishery has led to conflicting objectives among stakeholders, which poses complex challenges for regional management. Stakeholder representatives and managers were engaged via a participatory workshop and subsequent one-on-one surveys to trial a structured decision-making process to identify effective ecosystem-based management strategies. We directly and indirectly elicited each stakeholder’s preferences for nine alternative management strategies by presenting them with the 10-year consequences of each strategy estimated from an ecosystem model of Tasmanian reef communities. These preferences were included in cost-effectiveness scores that were averaged (across stakeholders) to enable strategy ranking from most to least cost-effective. Rankings revealed strategies that included sea urchin removal or translocation of predatory lobsters were the most cost-effective. However, assessment of stakeholders’ individual cost-effectiveness scores showed some disparity among stakeholders’ preferences in high ranking strategies. Additionally, evaluating inconsistencies within some stakeholders’ scores that included direct or indirect preferences revealed conflicting objectives and cognitive bias as the most plausible explanations for these inconsistencies. Our study illustrates how structured decision-making can effectively facilitate ecosystem-based management by engaging stakeholders step-by-step towards management strategy implementation, identifying psychological barriers to decision-making and promoting collective learning.
Small-scale fisheries (SSF) remain a largely under-assessed and overlooked sector by governments and researchers, despite contributing approximately 50% to global fish landings and providing food and income for millions of people. The multi-species, multi-gear and data-poor nature of SSF makes implementation of traditional single-species management approaches – like catch-quotas or size limits – particularly challenging and insufficient. A more holistic approach is thus required, which demands assessment of ecological impacts. Here we carried out an estimation of selected ecological indicators of the impact of fisheries (mean length, maximum body size, mean trophic level, trophic and spatial guilds, threatened species and landed by-catch) based on the nominal catch of different gears in three representative SSF along the Colombian Pacific using landings data collected in multiple years (2011–2017). Results showed that taxonomic, size-based, functional and conservation features of the nominal catch vary greatly with geographical location and gear type used. Overall, handlines and longlines tend to select larger sizes and higher trophic levels than nets, but they also catch a higher proportion of intrinsically vulnerable species and species of conservation concern. This challenges the idea that more selective gears have overall lower ecological impacts. In contrast, nets target a wider size range – although focusing on small or medium sized fish – and include a higher diversity of trophic and spatial guilds, which could arguably be considered a more “balanced harvest” type of fishing that retains ecosystem structure and functionality. Bottom trawls, though, exhibited a relatively high percentage of landed by-catch, an undesirable feature for any fisheries in terms of sustainability. We propose that the assessment of a suite of ecological indicators, like those implemented here, should be included as part of periodic evaluations of multi-gear and multi-species SSF in tropical coastal areas, as a practical step toward ecosystem-based fisheries management.