Geographical location of the study area and main geographical features of the Tunisian exclusive economic zone (EEZ).

<p>The axes indicate degrees latitude and longitude.</p

Contributions of the variables for the GDM.

<p>Change in the deviance when the variable was removed from the model is shown, as well as the percentage contribution to the model (sea surface salinity (SSS), sea surface temperature (SST)).</p><p>Contributions of the variables for the GDM.</p

Observed (a) and GDM predicted (b) spatial patterns of beta diversity for demersal exploited marine species assemblages along the Tunisian coasts and the slope of the predicted beta diversity (c).

<p>Grid cells mapped in a similar color are predicted to have similar species assemblages, while cells mapped in a very different color are predicted to be highly dissimilar in composition.</p

Biogeographical regions resulting from a Fuzzy C means cluster analysis and radial plots of the environmental variables.

<p>Radial plots result from the multiplication of the fuzzy membership of each region by the value of each variable (GG: Gulf of Gabes, ENCA: Eastern and Northern Coastal Areas, OA: Offshore Areas).</p

Modeling framework adopted in the present study.

<p>Modeling framework adopted in the present study.</p

Modeling of Beta Diversity in Tunisian Waters: Predictions Using Generalized Dissimilarity Modeling and Bioregionalisation Using Fuzzy Clustering

<div><p>Spatial patterns of beta diversity are a major focus of ecology. They can be especially valuable in conservation planning. In this study, we used a generalized dissimilarity modeling approach to analyze and predict the spatial patterns of beta diversity for commercially exploited, demersal marine species assemblages along the Tunisian coasts. For this study, we used a presence/absence dataset which included information on 174 species (invertebrates and fishes) and 9 environmental variables. We first performed the modeling analyses and assessed beta diversity using the turnover component of the Jaccard’s dissimilarity index. We then performed nonmetric multidimensional scaling to map predicted beta diversity. To delineate the biogeographical regions, we used fuzzy cluster analysis. Finally, we also identified a set of indicator species which characterized the species assemblages in each identified biogeographical region. The predicted beta diversity map revealed two patterns: an inshore-offshore gradient and a south-north latitudinal gradient. Three biogeographical regions were identified and 14 indicator species. These results constitute a first contribution of the bioregionalisation of the Tunisian waters and highlight the issues associated with current fisheries management zones and conservation strategies. Results could be useful to follow an Ecosystem Based Management approach by proposing an objective spatial partitioning of the Tunisian waters. This partitioning could be used to prioritize the adjustment of the actual fisheries management entities, identify current data gaps, inform future scientific surveys and improve current MPA network.</p></div

SEAwise report on the effects of fishing on food webs and community diversity aimed at populating the MSFD Descriptor 4 and based on food web and end-to-end modelling.

The SEAwise project works to deliver a fully operational tool that will allow fishers, managers, and policy makers to easily apply Ecosystem Based Fisheries Management (EBFM) in their fisheries. This SEAwise report describes work that aims to provide a strong evidence base supporting the use of ecological indicators in fisheries management through statistical studies and end to end modelling. Our aim is to support the use of ecological indicators to guide managers towards strategies that lead to an ecologically safe space for fisheries, which we define as a range of states that provide yields for sustainable fisheries, maintains ecosystem functions and leads to low risk of overexploitation of species and loss of diversity. We show from an analysis of the past, using stock assessment model products for the northeast Atlantic and observations from scientific survey data of the North Sea, that fishing has already impacted ecosystems. Fishing on commercial fish stocks altered the balance of functional groups within the ecosystem of the northeast Atlantic, with depletions in the biomass of fish during the 1980s followed by stock rebuilding since the early 2000s, such that the biomasses of benthivorous fish and planktivorous fish are now much greater than that of piscivorous fish, which may be a sign of an improving ecosystem. Within the North Sea, fishing also appeared to have depleted the biomass of fish during the 1980s (particularly in the southern North Sea) and led to a change in the composition of species and the proportion of large individuals in the ecosystem (particularly in the northern North Sea).We use comparative ecosystem modelling, employing multiple model types, to investigate the response of foodweb and community diversity indicators under a range of fishing strategies. We consider ‘no fishing’ scenarios, under prevailing environmental conditions, as a measure of the unimpacted state of the ecosystem i.e., its carrying capacity. Our modelled unimpacted state is our ‘yardstick’ - a standard from which we can measure the impact on the ecosystem due to current levels of fishing in the current conditions. We propose that the depletion of species, the difference in biomass of each species from their unimpacted levels under prevailing environmental conditions, can provide a basis from which to evaluate the risk of loss across impacted groups within the ecosystem.We investigate if any of our selected food web and community indicators, including those used within the regional sea convention OSPAR, can support the use of assessment thresholds that may help managers reduce the risk of depletion of species or degradation of ecosystems by fishing. We explore management scenarios, linked to changes in levels of fishing impact due to current fisheries (so not favouring one type of fishing over another), to demonstrate how reducing or increasing activity levels will alter the risk of depletion of species and demonstrate how ecological indicators are expected to change given alterations in the structure of the ecosystem. We contrast these management scenarios to additional scenarios in which seabed-impacting gears only are restricted to avoid damage to habitats. This latter scenario promotes fishing on pelagic fish, such as herring and sprat, in the future and inhibits trawling for demersal fish such as sole, plaice and cod.In each model, we find clear predictable relationships between fishing mortality overall (averaged across all model groups) and the depletion risk within the ecosystem. The biomass of apex predators typically decreases as fishing mortality increases. Similarly, as the size-structure of demersal fish communities decreases, risk within the communities increase. In contrast, the balance of trophic guilds in the ecosystem and the Shannon diversity overall or by group respond in differing ways (increases and decreases with increased fishing) dependent on the type fishing strategies modelled. The indicator targets for recovery and risk-based limits proposed here will be explored further in WP6 of the project.Read more about the project at www.seawiseproject.org</p

SEAwise Report on the key drivers of stock productivity and future environmental scenarios

An ecosystem approach to fisheries management requires the consideration of commercial species as components of an ecosystem and the acknowledgement of the links between their productivity and the surrounding environment. To provide a knowledge base for such links, SEAwise consulted stakeholders throughout Europe and conducted a systematic review of the scientific literature. The systematic review resulted in 2050 articles from the literature search that were screened for their tile and abstract. 516 of them were retained for data extraction. The majority of studies were conducted in the Baltic Sea and the North Sea, followed by the Western Waters, and with only a few dozen papers in the Mediterranean Sea. Cod and herring were the most studied species, temperature and more generally climate and hydrodynamics indicators were the main drivers investigated, and reproduction was the main productivity-related process. The output of the systematic review is a database of scientific articles organised by regions, species, environmental drivers and productivity-associated processes and where outcomes, but also spatial and time scales, analytical methods etc. are described in a standardised fashion. This database will be analysed in the coming months and used in the downstream tasks of WP3. The most frequently driver identified by stakeholders across regions was climate change followed by species interactions, cod, pollution, commercial fish/shellfish and plankton. Climate change effects on stocks through temperature and salinity are relatively well covered in the literature as are effects of plankton and species interaction. Studies of the effects of pollution do not occur frequently and as a consequence require a dedicated effort is made in SEAwise to remedy this. Species reported frequently by the stakeholders included cod, seabass, sardine, sole, crabs, flatfish, Norway lobster, octopus, shrimps, herring, sprat, anchovy, hake, new species (species increasing in abundance as a result of climate change as well as invasive species of commercial interest) and sandeel. Among these, more than 10 papers were retrieved for cod, sardine, sole, herring, sprat, selected flatfish, anchovy, hake and sandeel. For the remaining species, a dedicated effort must be made in SEAwise if they are to be included in stock models.  This report describes results of the SEAwise project. More information about the project can be found at https://seawiseproject.org/</p

SEAwise Report on the key species and habitats impacted by fishing

The implementation of ecosystem-based fisheries management requires knowledge on the ecological impact of fishing activities on species and their habitats – those both targeted and not targeted by fisheries. To identify which ecological impacts are key and what is known about them, SEAwise consulted stakeholders through European Advisory Councils and conducted a systematic review of the scientific literature to map the available knowledge and evidence. Specific reference was given to the bycatch of Protected, Endangered and Threatened (PET) species, benthic habitats, food webs and biodiversity, and impact from fisheries-related litter and ghost nets.  At the stakeholder consultations, sharks and/or elasmobranchs, turtles, species interactions, and seals or marine mammals were identified as top ranked in at least three out of the five regions. Other terms identified by at least two Case Study regions were: seabirds, sensitive species, benthic habitats, litter, PET species, invasive species and species interactions.  Relevant data were extracted from 549 retained papers. The majority of studies were conducted in the Mediterranean Sea, whereas only few papers reported on fishing impacts in the Baltic Sea (see figure below). Bony fish (teleosts) and benthos were the most studied ecosystem components in all Case Study regions, whereas marine mammals and cartilaginous fish were often studied in relation to bycatch of PET species.  Out of the 549 papers, most of them were related to fishing impacts on food webs and biodiversity and benthic habitats, followed by bycatch of PET species and other fishing impact studies (not related to any task). Fewest studies were related to the impact of fisheries-related litter and ghost nets. Demersal trawls were by far the most studied gear in studies on commercial fishing impacts. For recreational fisheries, hooks and lines, in particular angling, was the most studied fishing activity.  Among the items identified by the stakeholders, marine mammals, seabirds and reptiles were all covered in at least 25 papers each, indicating that there is a considerable body of knowledge even though not all areas may have information for all species. Litter was the key item that was least frequently reported on in the literature, especially outside the Mediterranean, where scientific papers were rare. As a consequence, areas outside the Mediterranean may lack information for further analysis unless a dedicated effort is made in SEAwise to remedy this. The regional differences in topics identified by stakeholder scoping did not reflect the regional amount of papers available.  This report describes results of the SEAwise project. More information about the project can be found at https://seawiseproject.org/</p

SEAwise Report on consistency of existing targets and limits for indicators in an ecosystem context

The SEAwise project works to deliver a fully operational tool that will allow fishers, managers, and policy makers to easily apply Ecosystem Based Fisheries Management (EBFM) in their fisheries. This SEAwise report investigates the consistency of existing targets and limits from the Common Fisheries Policy (CFP) and the Marine Strategy Framework Directive (MSFD). Trade-offs between different objectives (ecological, economic, social), targets and limits are highlighted. A wide range of model types (from bio-economic to full ecosystem models) has been applied to various case study areas across the North East Atlantic and Mediterranean. Although model predictions are by nature uncertain, this study provides important information on likely inconsistencies between existing targets and limits and trade-offs expected under ecosystem- based fisheries management (EBFM). The scenarios investigated include the current range of management applied in terms of the Maximum Sustainable Yield (MSY) concept (i.e. strict MSY approach vs. Pretty Good Yield (PGY) approach allowing sustainable deviations from single species FMSY point estimates). The landing obligation is a key aspect of current fisheries management and was fully considered, in particular for mixed demersal fisheries.Maintaining current fishing effort without further management measures was the least sustainable option in nearly all cases studies. This approach led to increased risk of stocks falling below critical biomass limits. Although the fishing effort adaptions needed is highly case specific, this indicates that further management measures are likely to be needed to ensure a sustainable exploitation of all stocks.Scenarios applying a strict MSY approach in combination with the landing obligation (i.e. FMSY as upper limit with fisheries ending when the first stock reaches FMSY) in most case studies led to the lowest fishing effort. This had positive effects on MSFD related indicators such as bycatch of Protected, Endangered and Threatened (PET) species, benthic impact and the Large Fish Indicator as well as global indicators such as CO2 emission or ecosystem-based indicators like catch per km2. However, this scenario often led to the lowest catches from mixed demersal fisheries due to strong choke effects because fleets had to stop when their first quota was exhausted. This reduces social indicators such as food security, employment and wages. In terms of economic performance, the gains and loses were highly case specific. Scenarios applying the Pretty Good Yield concept and allowing sustainable deviations from the FMSY point estimate when stocks are in a healthy state often outperformed the scenarios applying FMSY as strict upper limit. Such scenarios, applying a more flexible interpretation of the MSY concept, led to reduced fishing effort compared to the status quo effort, but relaxed choke situations in mixed demersal fisheries to some extent leading to higher gross profits and in some case studies also to higher catches. Hence, they may constitute a compromise between the need to attain social as well as ecological objectives. Whether the associated effort levels lead to conflicts with MSFD objectives must be analysed when more internationally agreed thresholds become available for e.g., bycatch of PET species or benthic impact.The majority of case studies exceeded suggested thresholds for the global ecosystem indicators catch per km2 or primary production even under scenarios with high effort reductions. This can be explained to some extent by the fact that these indices are mainly driven by pelagic and industrial fisheries not always part of the models applied. Nevertheless, it indicates potential conflicts with such more holistic ecosystem indicators in their current form.Additional trade-offs in terms of yield were identified within the food web if e.g., demersal piscivorous predators feed on small pelagic fish and both groups are fished. Further, in case studies where small-scale fisheries (SSF) play an important role (e.g., Eastern Ionian Sea) additional trade-offs became apparent as different scenarios led to different ratios between revenues from small scale fisheries and revenues from large-scale fisheries. This adds another level of complexity when such aspects need to be taken more into account in future fisheries management under EBFM.The modelling assumed current selectivities and catchabilities will be maintained in the future. Especially trade-offs arising from fleets having to stop fishing when their first quota is exhausted or when e.g., a threshold for bycatch of PET species is reached may be resolved by improving selectivities via technical measures (e.g., closed areas or innovative gears) in the future. Deliverable 6.8 in month 36 will test such scenarios. Furthermore, the list of indicators and their targets and limits will be updated based on research within and outside SEAwise. Predictive capability of models will be enhanced by incorporating improved biological and economic sub-models in relation to environmental change. Climate change scenarios will be run and new harvest control rules (HCRs), proposed by SEAwise, will be tested. Finally, consistent targets and limits will be proposed for implementing EBFM.</p