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Biomass ratios for simulations involving an additional fictive fleet in the Banc (A) and the loss of the Banc as a habitat (B) for the three models (P30, Base, M30) by group of species (31spp, and coastal, pelagics and shelf functional groups).
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Most modelling studies addressed the effectiveness of marine protected areas (MPA) for fisheries sustainability through single species approach. Only a few models analysed the potential benefits of MPAs at the ecosystem level, estimating the potential export of fish biomass from the reserve or analysing the trophic relationships between organisms i...
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... The area is a home to a rich marine fauna, including endemic species (Kide et al. 2016, Séret andNaylor 2016), as well as iconic species such as turtles (Hama et al. 2019), dolphins (Araujo and Campredon 2016), and large elasmobranchs (Valadou et al. 2006, Séret andNaylor 2016). Banc d'Arguin is also a major nursery and breeding ground for many endangered shark and ray populations (Valadou et al. 2006) and supports important bonyfish stocks in the region (Jager 1993, Schaffmeister et al. 2006, Guénette et al. 2014, Correia et al. 2020). The park is mostly famous for its wealth and richness in avian biodiversity (Altenburg et al. 1982, Wolff andSmit 1990), including two endemic species (Oudman et al. 2020) and the largest seabird colonies in West Africa (Campredon 2000, Araujo andCampredon 2016). ...
... Rating of tunnel Orientation is taken as 0 and -12. '0' orientation rating is taken for tunnel section having very favorable tunneling condition as tunnel direction drives with dip of strata While -12 rating is taken for tunnel sections having strike parallel to tunnel axis [7]. Groundwater condition is wet at one section in initial chain age section while at other sections it is damp. ...
Most of hydropower tunnels have squeezing problems due to weak rock mass quality and high overburden. The induced stress level exceeds the strength of rock mass tunnel fails. Stress plays a crucial role in developing brittle fractures, rock strength reduction and rock mass instabilities the critical stress is an indicator for the support design of tunnel. To quantify stress state and deformation of circular tunnel, an empirical, semi analytical and a two-dimensional boundary element numerical analysis have been made in this paper. Initially, rock mass characterization is carried out by using Q and RMR methods which defined rock mass as poor to good and fair respectively. Then for identification of squeezing empirical approaches are used, results shown that there is no squeezing in the tunnel. However, 200 m stretch of tunnel undergoes severe squeezing as identified by Hoek and Marinos approach which is further refined by using Numerical program phase2 which yields displacement values quiet nearer to values obtained by semi-analytical approach by considering rock mass as plastic material. Tunnel support is estimated by using Q and RMR systems respectively which is verified by Numerical analysis.
... To this end, it presents new evidence from simulations of subsidy reform conducted using ecosystem models that reflect fisheries in three key regions around the world-the Mauritanian EEZ, the East China Sea, and the northern South China Sea. These fisheries were selected based on their importance to their associated countries and ecosystems as well as the availability of previously constructed ecosystem models (Pauly, Christensen, and Walters 2000) that were updated for the purposes of studying subsidies (Cheung 2007;Guenette, Meissa, and Gascuel 2014). Subsidies in each of these fisheries are very large, both in their absolute magnitude and as a proportion of gross fishery revenues (table 10.1), emphasizing the importance of ensuring that these fisheries remain economically productive. ...
... The Mauritanian exclusive economic zone (EEZ) extends to about 33,224 square kilometers with a depth of less than 200 meters. It includes a marine protected area, the Banc d'Arguin National Park, which covers about 6,450 square kilometers (Guenette, Meissa, and Gascuel 2014). The shelf ecosystem is enriched by the effects of an upwelling, with diverse fish species. ...
... The shelf ecosystem is enriched by the effects of an upwelling, with diverse fish species. The domestic fishery consists mainly of small-scale, artisanal fishing boats (Gascuel et al. 2007) that fish for mullets, especially in the Banc d'Arguin National Park, where only park residents operating small sailboats are allowed to fish (Guenette, Meissa, and Gascuel 2014). A larger proportion of the catch emanates from foreign vessels, both pelagic and demersal fleets, flagged in China, the European Union, the Russian Federation, and other countries (Gascuel et al. 2007). ...
Clean air, land, and oceans are critical for human health and nutrition and underpin much of the world’s economy. Yet they suffer from degradation, poor management, and overuse due to government subsidies. "Detox Development: Repurposing Environmentally Harmful Subsidies" examines the impact of subsidies on these foundational natural assets. Explicit and implicit subsidies—estimated to exceed US$7 trillion per year—not only promote inefficiencies but also cause much environmental harm. Poor air quality is responsible for approximately 1 in 5 deaths globally. And as the new analyses in this report show, a significant number of these deaths can be attributed to fossil fuel subsidies. Agriculture is the largest user of land worldwide, feeding the world and employing 1 billion people, including 78 percent of the world’s poor. But it is subsidized in ways that promote inefficiency, inequity, and unsustainability. Subsidies are shown to drive the deterioration of water quality and increase water scarcity by incentivizing overextraction. In addition, they are responsible for 14 percent of annual deforestation, incentivizing the production of crops that are cultivated near forests. These subsidies are also implicated in the spread of zoonotic and vector-borne diseases, especially malaria. Finally, oceans support the world’s fisheries and supply about 3 billion people with almost 20 percent of their protein intake from animals. Yet they are in a collective state of crisis, with more than 34 percent of fisheries overfished, exacerbated by open-access regimes and capacity-increasing subsidies. Although the literature on subsidies is large, this report fills significant knowledge gaps using new data and methods. In doing so, it enhances understanding of the scale and impact of subsidies and offers solutions to reform or repurpose them in efficient and equitable ways. The aim is to enhance understanding of the magnitude, consequences, and drivers of policy successes and failures in order to render reforms more achievable.
... The PNBA is one of the largest parks in West Africa and plays a crucial role in maintaining the bird biodiversity it shelters. The park also protects and contribute to the productivity of the marine ecosystems and halieutic resources of the Mauritanian Exclusive Economic Zone (EEZ; [47]), from which the country derives up to 10% of its Gross Domestic Product through fisheries [48]. Furthermore, the park is home to the Imraguen, a local ethnic population living in harmony with its environment for several centuries and whose ancestral fishing techniques are also part of the park's immaterial heritage. ...
Background: The National Park of Banc d’Arguin (PNBA, Mauritania) was founded in 1976 to preserve the largest West African wintering area for shorebirds. In the face of increasing pressures, the PNBA’s authorities have launched an appeal to determine the park’s socio-economic value to adjust its management plan better.
Methods: In this context, we have created an exhaustive inventory of known characteristics of bird species present in the PNBA to investigate their potential in terms of ecosystem services for local populations. Two regulating and supporting services were also valued based on data availability: nutrients input and carcasses removal.
Results: We found that 53% of the 233 bird species associated with the PNBA are highly dependent on the park and its coastal and marine ecosystems for their life cycle. We were also able to identify services with a high potential for the park, such as nutrient cycling and bird-watching. We finally valued nutrients input and carcasses removal at € 1.8 to € 133.7 million/year and € 2900 to € 4800/year, respectively.
Conclusion: This study highlights the importance of protecting the PNBA’s birds beyond the sole ornithological interest behind its creation and reinforces the argument about the importance of this protected area in terms of conservation.
... Rating of tunnel Orientation is taken as 0 and -12. '0' orientation rating is taken for tunnel section having very favorable tunneling condition as tunnel direction drives with dip of strata While -12 rating is taken for tunnel sections having strike parallel to tunnel axis [7]. Groundwater condition is wet at one section in initial chain age section while at other sections it is damp. ...
Most of hydropower tunnels have squeezing problems due to weak rock mass quality and high overburden. The induced stress level exceeds the strength of rock mass tunnel fails. Stress plays a crucial role in developing brittle fractures, rock strength reduction and rock mass instabilities the critical stress is an indicator for the support design of tunnel. To quantify stress state and deformation of circular tunnel, an empirical, semi analytical and a two-dimensional boundary element numerical analysis have been made in this paper. Initially, rock mass characterization is carried out by using Q and RMR methods which defined rock mass as poor to good and fair respectively. Then for identification of squeezing empirical approaches are used, results shown that there is no squeezing in the tunnel. However, 200 m stretch of tunnel undergoes severe squeezing as identified by Hoek and Marinos approach which is further refined by using Numerical program phase2 which yields displacement values quiet nearer to values obtained by semi-analytical approach by considering rock mass as plastic material. Tunnel support is estimated by using Q and RMR systems respectively which is verified by Numerical analysis.
... La contribution du parc national du Banc d'Arguin pour la pêche en Mauritanie et plus généralement en Afrique de l'Ouest est très importante Guénette et al., 2014). Ce parc couvrirait environ 20% de linéaire côtier mauritanien, pour une création de valeur ajoutée liée à la pêche de 3,2 milliards d'ouguiyas mauritaniennes par an, soit 71 millions d'euros . ...
... Dans le cas du parc national du Banc d'Arguin, la plupart des critères sont rencontrés : le service est relativement diffus -à savoir que le parc fourni via ses habitats côtiers les conditions propices à la garantie du stock halieutique pêché par l'UE -mais le lien entre le PSE et les pêcheries dans la ZEE mauritanienne a déjà été étudié et validé de façon robuste (Guénette et al., 2014 ;. L'acheteur est l'UE (bien que les usagers du service soient les armateurs européens), tandis que les bénéficiaires -le parc national et le fonds Bacomab -exercent une réelle influence sur la conservation des habitats côtiers dans le parc. ...
Les Aires Marines Protégées (AMP) étudiées abritent de grandes superficies de mangroves, d’herbiers, de récifs rocheux peu profonds et d’autres habitats propices au cycle de vie de nombreuses espèces marines, et notamment de certaines espèces de petits poissons pélagiques qui sont très consommés dans la région. Ces AMP permettent de conserver ces milieux naturels, en assurant un suivi et en
limitant les impacts humains. La pêche et les autres activités extractives y sont par ailleurs réglementées. Les AMP assurent le fonctionnement et la conservation des écosystèmes, qui fournissent de nombreux services : tout d’abord, ces AMP sont souvent situées sur le parcours de migration des espèces de petits pélagiques. Elles constituent pour la plupart, des zones de reproduction et de nurserie pour les petits pélagiques et pour de nombreuses autres espèces marines. Elles sont aussi des zones de refuge et d’alimentation. En outre, les habitats naturels situés dans ces
AMP séquestrent du carbone, assurent une protection côtière, sont des supports au tourisme, sont des lieux de culte ou encore agissent sur la qualité de l’eau.
Les espèces de petits pélagiques (sardinelles, chinchards, ethmaloses, sardines, maquereaux) sont très convoitées dans la région et jusque dans les pays ouest-africains qui n’ont pas d’accès à la mer. Leur exploitation garantit la sécurité alimentaire et l’emploi à des dizaines de millions de personnes. En outre, ces espèces font l’objet d’une pêche industrielle par de nombreuses flottes étrangères (Europe, Russie, Asie, etc.) pour la consommation humaine ou pour alimenter les usines de farines de poisson. Cependant ces espèces sont pour la plupart en état de surexploitation, et la pérennité de leurs stocks est donc menacée.
La valeur monétaire des services fournis par les habitats naturels des six (06) AMP de la zone d’étude est estimée à 45,02 milliards de FCFA chaque année (soit 68,628 millions d’euros). Cette valeur monétaire n’inclue pas les services spirituels. La valeur économique par kilomètres carré est en moyenne de 16,140 millions de FCFA/an (soit 24'603 euros), avec un pic à plus de 70 millions de FCFA par km2 (plus de 100’00 euros) pour l’AMP d’Abéné. Les services qui possèdent la plus forte valeur économique sont la production de biomasse en petits pélagiques (16,57 milliards de FCFA par an
cumulés pour les six AMP), la séquestration de carbone (13,60 milliards FCFA par an) et la pêche (12,2 milliards FCFA par an). La production de biomasse dépasse la pêche en termes de valeur économique, ce qui démontre que les AMP jouent un rôle de « réservoir de ressources » qui se dissémineront ensuite à l’ensemble du littoral de la région. Par ailleurs, si l’état de santé des habitats naturels des AMP s’améliorait, la valeur de leurs services augmenterait en conséquence.
Afin de maintenir la bonne santé des écosystèmes à haute valeur présents dans les AMP, les équipes de gestion ont besoin de moyens techniques, financiers et humains plus importants. Tandis que les moyens sont insuffisants dans les AMP, de nombreux usagers qui bénéficient (directement ou indirectement) des services fournis par ces AMP n’en payent pas le prix. C’est le cas notamment des flottes de pêche industrielles, qui prélèvent des quantités considérables de poissons, sans pour autant participer à l’effort de conservation des milieux naturels essentiels au cycle de vie de leurs captures. La mise en place de paiements pour les services écosystémiques (PSE) apparaît dès lors comme un mécanisme financier pertinent pour garantir la conservation des milieux naturels marins et côtiers. Les efforts consentis par les flottes industrielles seraient relativement faibles, au regard des bénéfices qui
échoiraient aux institutions en charge des AMP. L’Union Européenne et la Mauritanie ont d’ores et déjà franchi le pas depuis plusieurs années, en incorporant un mécanisme de PSE à destination du parc national du Banc d’Arguin dans le protocole de l’accord de pêche permettant à l’UE de pêcher en Mauritanie. De tels PSE pourraient s’étendre aux autres pays avec lesquels l’UE entretien des accords de pêche, mais aussi aux flottes industrielles domestiques et étrangères qui contractent des accords vés. La mise en place de tels mécanismes démocratiserait la mise en œuvre du principe d’ « usager-payeur », en parallèle au principe déjà bien connu de « pollueur-payeur ».
... We calculated the relative effect size of these rates (changes in direct mortality, vulnerability rate, and effective search rate) using the absolute values under different climate scenarios compared to the control condition (Table S2). We incorporated the effect of warming and acidification (relative effect size of different rates) in our modelling approach through forcing functions that affect the consumption and production of trophic groups at a temporal scale Alva-Basurto and Arias-González, 2014;Cornwall and Eddy, 2015;Guénette et al., 2014). The climate scenarios were assumed to focus on the year 2100 and the control conditions in 2015. ...
One of the biggest challenges in more accurately forecasting the effects of climate change on future food web dynamics relates to how climate change affects multi-trophic species interactions, particularly when multiple interacting stressors are considered. Using a dynamic food web model, we investigate the individual and combined effect of ocean warming and acidification on changes in trophic interaction strengths (both direct and indirect) and the consequent effects on biomass structure of food web functional groups. To do this, we mimicked a species-rich multi-trophic-level temperate shallow-water rocky reef food web and integrated empirical data from mesocosm experiments on altered species interactions under warming and acidification, into food-web models. We show that a low number of strong temperature-driven changes in direct trophic interactions (feeding and competition) will largely determine the magnitude of biomass change (either increase or decrease) of high-order consumers, with increasing consumer biomass suppressing that of prey species. Ocean acidification, in contrast, alters a large number of weak indirect interactions (e.g. cascading effects of increased or decreased abundances of other groups), enabling a large increase in consumer and prey biomass. The positive effects of ocean acidification are driven by boosted primary productivity, with energy flowing up to higher trophic levels. We show that warming is a much stronger driver of positive as well as negative modifications of species biomass compared to ocean acidification. Warming affects a much smaller number of existing trophic interactions, though, with direct consumer-resource effects being more important than indirect effects. We conclude that the functional role of consumers in future food webs will be largely regulated by alterations in the strength of direct trophic interactions under ocean warming, with ensuing effects on the biomass structure of marine food webs.
... The Park plays a crucial role in the protection of those ecosystems and the provision of associated services in the Gulf d'Arguin. Indeed, the Park is essential for the renewal of fisheries resources in the exclusive economic zone of Mauritania (Guénette et al., 2014) and more broadly at a sub-regional level and in the sequestration of atmospheric carbon in a country with low terrestrial vegetation. Conservation of the natural environment and sustainable development of populations are the main objectives of the PNBA. ...
Coastal marine ecosystems ensure fundamental hydro-ecological functions and support high levels of biodiver- sity, besides being an important resource for local populations. These biocenosis have been increasingly threatened by human pressures (e.g. pollution, overfishing) along with climate change, which may have a dramatic impact on them. The National Park of Banc d’Arguin (PNBA) in Mauritania, one of the biggest parks in Western Africa, is a RAMSAR zone (classified by UNESCO since 1989) that plays a major role in (i) the main- tenance of marine biocenosis, (ii) the protection of the ecosystems and (iii) the sequestration of carbon dioxide. Ecosystem databases and associated maps of the PNBA are out of date and limited to the southern and central parts of the park: updating is thus needed. In this paper, a supervised Support Vector Machine (SVM) was deployed using high-resolution images from Sentinel-2 combined with field data to map marine biocenosis of the PNBA. The results highlight that Sentinel-2 shows good classification accuracy for mapping marine biocenosis (>80% overall accuracy and a kappa index of 0.75), including seagrass beds. Also, the use of high-resolution sensors like SPOT-6 (1.5 m pixels) can overcome the limitations of Sentinel-2 (10 m pixels) when it comes to detecting small ecosystems distributed in patches. The use of freely-downloadable Sentinel-2 data, processed using geoinformatic freeware, make the methodology reproducible, affordable and easily transferable to local actors of biodiversity conservation for long term usage.
... obs.). Although fishing pressure through artisanal practices and bycatch rates within the MPAs are also substantial (Campredon and Cuq, 2001;Valadou et al., 2006;Diop and Dossa, 2011), fishing effort of industrial fleets at the borders of these MPAs could potentially have negative effects on the population status of marine megafauna utilizing these coastal areas (Guénette et al., 2014;Di Lorenzo et al., 2016). Herein we describe the industrial fishing activity within the West African region between 2012 and 2018 with three main objectives: (1) to analyze the spatiotemporal extent of gear-specific fishing efforts within the region, (2) to map fishing activity in the direct vicinity of the two largest West African MPAs, PNBA and the BA, and (3) to link the industrial fishing effort with seasonal bycatch of elasmobranchs (i.e., sharks FIGURE 1 | Defined study area indicating the Exclusive Economic Zones (EEZs; dashed lines) and Marine Protected Areas (MPAs; green lines) within the West African region. ...
Marine Protected Areas (MPAs) are increasingly implemented to facilitate the conservation of marine biodiversity and key habitats. However, these areas are often less effective to conserve mobile marine species like elasmobranchs (i.e., sharks and rays). Industrial fishing near MPA borders possibly impacts vulnerable species utilizing these protected areas. Hence, we aimed to study spatiotemporal patterns of industrial fisheries near MPAs, in relation to the bycatch of elasmobranchs. Specifically, we analyzed the spatiotemporal fishing effort within the West African region, mapped fishing effort in the direct vicinity of the Parc National du Banc d’Arguin (PNBA, Mauritania) and the Bijagós Archipelago (BA, Guinea Bissau), and compared the seasonal overlap between elasmobranch bycatch and fishing effort near these MPAs. We combined Automatic Identification System (AIS) data and local fisheries observer data, and determined fishing effort for each gear type and compared this with bycatch of elasmobranchs. We found that industrial fishing effort was dominated by trawling, drifting longlines, and fixed gear types. Although no industrial fishing was observed within both MPAs, 72 and 78% of the buffer zones surrounding the MPAs were fished for the Banc d’Arguin and Bijagós, respectively. Within the Banc d’Arguin buffer zone, trawling and drifting longlines dominated, with longlines mainly being deployed in fall. In the Bijagós buffer zone, trawling and fixed gears were most prevalent. Fisheries observer data for Mauritania showed that elasmobranch catches increased during the most recent sampling years (2016–2018). Elasmobranch catches within the waters of Guinea Bissau peaked in 2016 and decreased in the following two years. Seasonal patterns in elasmobranch bycatch within the waters of both countries are likely caused by increased catches of migratory species. Catches of rays peaked in May and June for Mauritania, and in October for Guinea Bissau. Shark catches were highest in February and July in Mauritanian waters, and in May and October in the waters of Guinea Bissau. Our study indicates that industrial fisheries near the border of ecologically important MPAs may have potentially major implications for ecosystem functioning by the removal of (migratory) predatory species.
... This study found slightly greater numbers of eels in the second sampling period when fewer octopus were observed, so this observation supports this theory. In this respect, it is important to consider the intermediate trophic position of octopus too, as increasing the number of potential predators of octopus could reduce their abundances (Guénette et al. 2014). ...
Octopus cyanea is a species of particular economic importance for coastal regions in the tropical Indo-Pacific, including the Mauritian island of Rodrigues. At present, little is known about their habitat preferences and how this may impact on their abundance from fishing pressure. This study aimed to investigate how the abundance of this octopus and their potential den sites differed between three areas of Rodrigues lagoon, Mauritius which were subjected to differing levels of fishing pressure and in which other marine species competed for the same space. A series of surveys over two months was conducted to measure octopus numbers, counted holes and abundance of selected invertebrates in 1000 m² belt transects, In total, 503 holes were counted that would be suitable for octopuses, and 17 octopuses were observed within the holes. A highly fished lagoon area, contained the most potential den holes. The other organisms found in the counted holes were fish, including eels, urchins and holothurians. I attribute the seemingly low abundance of octopus compared to previous surveys overall to the time of year and the lack of suitable habitat within these areas. Octopus abundance throughout the lagoon is low despite it being within a Marine Protected Area and does not follow the expected patterns of abundance when subjected to differing levels of fishing pressure, that is, it was expected that more would be found in the best protected area. Application of improved knowledge of octopus biology and habitat preferences could provide better management plans for their protection.
