Fisheries exploitation has historically been considered as the strongest driver of fish population dynamics, while overfishing is the main cause of fish stock depletion at a global scale (Myers & Worm 2003; Tsikliras et al. 2015; Froese et al. 2018). Existing fisheries management practices (mainly based on single- or multi-species approaches) have been unsuccessful in sustainably exploiting fish stocks, because of weaknesses in management approaches, improper implementation and illegal fishing. Commercial and recreational fishing strongly impact all levels of biological organisation and community structure including organisms, habitats and ecosystems (Jackson et al. 2001) raising a pressing need for a holistic approach to managing fisheries in the context of an ecosystem, i.e. an ecocentric (ecosystem-centered or ecosystem-based) fisheries management. International conventions and agreements, and European, regional and national laws all require that marine exploited populations (stocks) have to be managed in a way that their biomass is large enough to produce maximum sustainable yields (MSY) for fisheries. In particular, the member states of the European Union (EU) agreed to end overfishing by 2020, while the Common Fisheries Policy (CFP) of the EU call for the rebuilding of the biomass of all commercially exploited fish and invertebrate stocks above levels that are capable of producing MSY. The first step to achieve this target was that fishing pressure had to be reduced to levels that would produce MSY by 2015, and this was later revised to 2020. According to the CFP, member states are obliged to adjust the fishing capacity of their fleets to their fishing opportunities, aiming to achieve a stable and enduring balance between them. The CFP also “seeks to apply the ecosystem-based approach to fisheries management, and to minimize the effect of fishing on the ecosystem”, while EU and United Nations (UN) policy seeks to protect Vulnerable Marine Ecosystems from destructive extraction activities. At the same time, the Marine Strategy Framework Directive (MSFD) aims for Good Environmental Status of European Seas by 2020, including the requirement that none of the commercial fish and shellfish are subject to overfishing but exhibit good stock status in terms of biomass, as well as age and size distributions indicative of a healthy stock. Concomitantly, the Maritime Spatial Planning Directive (MSP) aims to “regulate uses of the marine environment”, the EU Biodiversity Strategy for 2030 aims to halt the loss of biodiversity and ecosystem services, while the Green Deal and Blue Growth Strategy promote sustainable use of marine resources under a changing climate. Putting fisheries management decisions into a whole ecosystem context, therefore, requires a shift from traditional single-species management to a more complex archetype, namely, that of ecosystem-based fisheries management, which encompasses multi-species interactions, environmental forcing, habitat status and human activities.
Ecosystem Based Management (EBM) encapsulates the movement towards a more cooperative and holistic approach to marine resource management (Leslie & McLeod 2007). Ecosystem Based Fisheries Management (EBFM) recognises the combined physical, biological, economic, and social trade-offs affecting the fisheries sector, and the need to address these trade-offs when optimising fisheries yields from an ecosystem (Link 2010). In the Ecosystem Approach to Fisheries Management (EAFM), ecosystem factors are included in the stock assessment, while the social and political dimensions are not necessarily explicitly addressed (Pitcher et al. 2009).
The design of inter-active policies that aim to implement the ecosystem approach to fisheries management is better served through a holistic integrated approach to maintain ecosystem integrity, adopt a precautionary approach to fisheries and other uses of marine/coastal ecosystems with broad stakeholder participation, promote sector integration and safeguard livelihoods (Pikitch et al. 2004). This will require interdisciplinarity among scientists to achieve the best possible knowledge on the ecosystems as well as information on social and economic factors that affect the availability of ecosystem services within an ecosystem, including fishing. A more comprehensive and holistic knowledge base of the ecology of the ecosystem is required to form a reliable basis for fisheries management and policy. Understanding of the biology and ecology of all species is, in some areas, far from complete, and appropriate assessment models and decision-support tools need to be further developed. Filling the gaps in ecological and biological knowledge and assessing human (including consumer and producer) impacts on organisms, habitats and ecosystems are prerequisites for effective ecocentric management. Assessment of the status and trends of fisheries and stocks as well as their habitats, and evaluation of ecosystem health are also needed to implement ecosystem based management of fisheries and to monitor their effectiveness. Stocks that have no commercial interest have generally been overlooked and the conservation status of marine megafauna is unknown in many European areas, especially in the Mediterranean and the Black Sea.
In addition, knowledge of the oceanographic, biogeochemical, environmental and climate impacts on species, habitats and ecosystems is required for adjusting current management practices (adaptive management) to achieve fisheries sustainability and ecosystem health, while at the same time maintaining economic viability (Link 2010). We need to know the oceanographic characteristics of marine ecosystems and how these influence populations, food webs, and ecosystem dynamics. Mainstreaming scientific data into management and policy is also a challenging task. Often the data are available, but not accessible to policy makers as a tailored toolbox that fits their needs and capacity and balances their socio-economic preferences within ecological boundaries. An intermediate communication link and methods for accessing data that are more specifically tailored is required. In order to define the best adaptive management and to provide policy makers with tools and data for making robust management decisions, sources of uncertainty such as ecological and biological knowledge gaps and possible future conditions must be accounted for (Link et al. 2012). Tools for conducting simulations under deep uncertainty defined as “the condition in which analysts do not know or the parties to a decision cannot agree upon:
(1) The appropriate models to describe interactions among a system's variables.
(2) The probability distributions to represent uncertainty about key parameters in the models.
(3) How to value the desirability of alternative outcomes: (Lempert et al. 2003) are lacking and the extended use of technological advancements such as machine learning and artificial intelligence in fisheries management is still immature. Externalities to fisheries are often not considered in management because they are difficult to measure or because the tools to do so are not available. Addressing the trade-offs among the wide range of issues involved in ecosystem-based fisheries management, such as ecological principles, legal mandates, climate change and economic interests (Hart & Fay 2020) will hopefully shift towards the perception that ecocentric fisheries management, albeit demanding and challenging, is necessary and feasible option.