Braham C.-B.,Institute Mauritanien Of Recherches Oceanographiques Et Des Peches Imrop |
Braham C.-B.,IRD Montpellier |
Freon P.,IRD Montpellier |
Laurec A.,Population Dynamics and Modelling |
And 2 more authors.
Fisheries Research | Year: 2014
Sardinella spp. are the main species fished in Mauritanian waters. Logbook data (1991-2009) were used to standardise CPUE. This clearly revealed that the abundance of sardinella peaked in the warm season (July-September) which is the main, if not the only significant spawning season for round sardinella. This study does not directly confirm or falsify the common belief that the adults migrate from the Senegalese EEZ up to north of the 21°. N latitude, but it presents a variety of new hypotheses. If a single transboundary stock exists, part of its individuals, or a sub-stock, is probably more sedentary and remains in the permanent upwelling area located in northern Mauritania and southern Morocco. Between years, changes in abundance index are dominated by a decrease from 1996 to 2006, depending on the months taken into account, and especially whether or not the warm (spawning) season is considered. For a given month, the spatial distribution of sardinella shows limited differences between years. In the southernmost latitudes of the Mauritanian EEZ the seasonal pattern, which is dominated by high catch rates during the warm season, is much stronger after the year 2001, and then tended to increase year after year. Changes in species distribution and abundance during the twenty-year study period are difficult to relate to environmental dynamics. However, an inversion of the upwelling trend was observed in 2001, matching a change in the seasonality of sardinella catches, although the causality between the two phenomena could not be established. The increase in the abundance index of sardinella in the last five years, particularly during most of the core fishing season (July-September) might be due to favourable oceanographic conditions (higher upwelling index) and/or changes in the fishing strategies or efficiency. Before annual indices of abundance can be used in the future, it will be necessary to better understand possible changes in catchability during the warm/spawning season. © 2014 Elsevier B.V.
Bez N.,IRD Montpellier |
Braham C.-B.,Institute Mauritanien Of Recherches Oceanographiques Et Des Peches Imrop
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2014
In North West Africa, pelagic fisheries are an essential economic sector. However, the scientific community fails to perform satisfactory assessments of key pelagic species like sardinella, owing to a lack of relevant indices of abundance to tune the model. This paper provides an alternative acoustic index based on a semiquantitative modelisation of acoustic densities. Acoustic energy is split into binomial variables coding for null, low, medium, large, and very large densities. A multivariate geostatistical approach allows (i) mapping the spatial distribution of classes of densities and (ii) computing a new acoustic index of abundance for Sardinella aurita and Sardinella maderensis.We used the surveys of RV Fridtjof Nansen (1995-2006) and RV Al-Awam (2007-2010). Our results indicated that empirical spatial structures were highly stable over time for both between areas and surveys. Co-kriging maps also showed that sardinella had stable hot spots of distribution. The indices of abundance developed in the present study were tested in an assessment procedure and outperformed all the indices used routinely by the FAO-CECAF (Fishery Committee for the Eastern Central Atlantic) assessment working group.
Guenette S.,Agrocampus Ouest |
Meissa B.,Agrocampus Ouest |
Meissa B.,Institute Mauritanien Of Recherches Oceanographiques Et Des Peches Imrop |
Gascuel D.,Agrocampus Ouest
PLoS ONE | Year: 2014
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 inside and outside the MPA. Here, we propose to use food web models to assess the contribution of a MPA to the trophic functioning of a larger ecosystem. This approach is applied to the Banc d'Arguin National Park, a large MPA located on the Mauritanian shelf. The ecosystem was modeled using Ecopath with Ecosim, a model that accounts for fisheries, food web structure, and some aspects of the spatial distribution of species, for the period 1991'2006. Gaps in knowledge and uncertainty were taken into account by building three different models. Results showed that the Banc d'Arguin contributes about 9 to 13% to the total consumption, is supporting about 23% of the total production and 18% of the total catch of the Mauritanian shelf ecosystem, and up to 50% for coastal fish. Of the 29 exploited groups, 15 depend on the Banc for more than 30% of their direct or indirect consumptions. Between 1991 and 2006, the fishing pressure increased leading to a decrease in biomass and the catch of high trophic levels, confirming their overall overexploitation. Ecosim simulations showed that adding a new fleet in the Banc d'Arguin would have large impacts on the species with a high reliance on the Banc for food, resulting in a 23% decrease in the current outside MPA catches. We conclude on the usefulness of food web models to assess MPAs contribution to larger ecosystem functioning. © 2014 Guénette et al.
Collaborative information system for environnement and soutenable management of fisheries in Mauritania [SICP: Système d’information collaboratif pour l’environnement et la gestion durable des pêches en Mauritanie]
Beibou E.,Institute Mauritanien Of Recherches Oceanographiques Et Des Peches Imrop |
Beibou E.,IRD Montpellier |
Guitton J.,Agrocampus Ouest |
Barde J.,IRD Montpellier
Ingenierie des Systemes d'Information | Year: 2015
Research institutions are always struggling to adopt an effective system to manage their information assets. The effective management of various sources of information in fact depends on the integration and interoperability of information systems partners. The sources are always complementary, because they cover different themes. But, taken separately, they often provide a fragmented vision for a scientific question, hence the importance of their integration. Similarly, knowledge and expertise of the users of these various sources and actors in the field must be taken into account and integrated into the system, hence the importance of a collaborative tool. We will relate in this article how the SCIP at IMROP overcomes these difficulties by proposing an innovative approach based on mediation and collaboration. © 2015 Lavoisier.
Meissa B.,Institute Mauritanien Of Recherches Oceanographiques Et Des Peches Imrop |
Meissa B.,European University of Brittany |
Gascuel D.,European University of Brittany
ICES Journal of Marine Science | Year: 2014
The recent, rapid development of fishing in Mauritania offers a good case study for a comparative approach of the resilience of the species exploited there, in the face of increasing fishing pressure. First, we assessed the health of 22 demersal stocks with differing ecological requirements, demographic strategies, and states of exploitation. A dynamic production model was fitted in a framework of Bayesian statistics to abundance indices estimated from scientific trawl surveys or commercial catch per unit efforts. We show that 12 of the 22 stocks assessed are overexploited and 3 are fully exploited. The combined assessment of all 22 stocks demonstrates an overall overexploitation, with total demersal biomass decreasing by ∼75% since 1982 and fishing effort 30% higher than that at maximum sustained yield (40% higher for finfish). Second, relations between states of stocks and life history traits were analysed. The stocks of large and vulnerable species currently undergo the highest fishing pressure and are those that are the most overexploited. At the scale of the community represented by the stocks considered, surveys-based indictors of the mean intrinsic vulnerability, the mean maximum length, and the mean trophic level exhibit a significant decrease from 1990 to 2010. Changes observed in catch-based indicators depend on fishing strategies and are impacted by the recent development of the small-scale fishery. But indicators expressed as a function of a multiplier of fishing effort or fishing mortality clearly decrease, thus confirming that the intensification of exploitation leads to communities dominated by smaller species and lower trophic levels. We conclude that large and high trophic level species, such as white grouper, meagre, guitarfish, and smooth-hound, are markers of ecosystem health and should be considered as sentinel species. © 2014 International Council for the Exploration of the Sea.