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Andrello, M., Guilhaumon, F., Albouy, C., Parravicini, V., Scholtens, J., Verley, P., et al. (2017). Global mismatch between fishing dependency and larval supply from marine reserves. Nat. Commun., 8, 16039.
Résumé: Marine reserves are viewed as flagship tools to protect exploited species and to contribute to the effective management of coastal fisheries. Yet, the extent to which marine reserves are globally interconnected and able to effectively seed areas, where fisheries are most critical for food and livelihood security is largely unknown. Using a hydrodynamic model of larval dispersal, we predict that most marine reserves are not interconnected by currents and that their potential benefits to fishing areas are presently limited, since countries with high dependency on coastal fisheries receive very little larval supply from marine reserves. This global mismatch could be reversed, however, by placing new marine reserves in areas sufficiently remote to minimize social and economic costs but sufficiently connected through sea currents to seed the most exploited fisheries and endangered ecosystems.
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Ba, K., Thiaw, M., Fall, M., Thiam, N., Meissa, B., Jouffre, D., et al. (2018). Long-term fishing impact on the Senegalese coastal demersal resources: diagnosing from stock assessment models. Aquat. Living Resour., 31, 8.
Résumé: For the first time in Senegal, assessments based on both stochastic and deterministic production models were used to draw a global diagnosis of the fishing impact on coastal demersal stocks. Based one national fisheries databases and scientific trawl surveys data: (i) trends in landings since 1971 were examined, (ii) abundance indices of 10 stocks were estimated using linear models fitted to surveys data and commercial catch per unit efforts, and (iii) stock assessments were carried out using pseudo-equilibrium Fox and Pella-Tomlinson models and a Biomass dynamic production model fitted in a Bayesian framework to abundance indices. Most stocks have seen their abundance sharply declining over time. All stocks combined, results of stock assessments suggest a 63% reduction compared to virgin state. Three fifth of demersal stocks are overexploited and excess in fishing effort was estimated until 75% for the worst case. We conclude by suggesting that the fishing of such species must be regulated and an ecosystem approach to fisheries management should be implemented in order to monitor the whole ecosystem.
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Bakker, J., Wangensteen, O. S., Chapman, D. D., Boussarie, G., Buddo, D., Guttridge, T. L., et al. (2017). Environmental DNA reveals tropical shark diversity in contrasting levels of anthropogenic impact. Sci Rep, 7, 16886.
Résumé: Sharks are charismatic predators that play a key role in most marine food webs. Their demonstrated vulnerability to exploitation has recently turned them into flagship species in ocean conservation. Yet, the assessment and monitoring of the distribution and abundance of such mobile species in marine environments remain challenging, often invasive and resource-intensive. Here we pilot a novel, rapid and non-invasive environmental DNA (eDNA) metabarcoding approach specifically targeted to infer shark presence, diversity and eDNA read abundance in tropical habitats. We identified at least 21 shark species, from both Caribbean and Pacific Coral Sea water samples, whose geographical patterns of diversity and read abundance coincide with geographical differences in levels of anthropogenic pressure and conservation effort. We demonstrate that eDNA metabarcoding can be effectively employed to study shark diversity. Further developments in this field have the potential to drastically enhance our ability to assess and monitor elusive oceanic predators, and lead to improved conservation strategies.
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Cucherousset, J., & Villeger, S. (2015). Quantifying the multiple facets of isotopic diversity: New metrics for stable isotope ecology. Ecological Indicators, 56, 152–160.
Résumé: Abstract
Stable isotope analyses have emerged as an insightful tool for ecologists, with quantitative methods being developed to analyse data at the population, community and food web levels. In parallel, functional ecologists have developed metrics to quantify the multiple facets of functional diversity in a n-dimensional space based on functional traits. Here, we transferred and adapted metrics developed by functional ecologists into a set of four isotopic diversity metrics (isotopic divergence, dispersion, evenness and uniqueness) complementary to the existing metrics. Specifically, these new metrics are mathematically independent of the number of organisms analysed and account for the abundance of organisms. They can also be calculated with more than two stable isotopes. In addition, we also provide a procedure for calculating the levels of isotopic overlap (similarity and turnover) between two groups of organisms. These metrics have been implemented into new functions in R made freely available to users and we illustrated their application using stable isotope values from a freshwater fish community. Transferring the framework developed initially for measuring functional diversity to stable isotope ecology will allow more efficient assessments of changes in the multiple facets of isotopic diversity following anthropogenic disturbances.
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Dalongeville, A., Andrello, M., Mouillot, D., Albouy, C., & Manel, S. (2016). Ecological traits shape genetic diversity patterns across the Mediterranean Sea: a quantitative review on fishes. J. Biogeogr., 43(4), 845–857.
Résumé: AimWe set out to identify the determinants of the variation in genetic diversity among fish species and test whether multi-species genetic diversity is randomly distributed in space. LocationMediterranean Sea. MethodsWe collected genetic diversity data from 39 published studies on Mediterranean fishes (31 species) along with the spatial coordinates of the sampling sites. We focused on microsatellite heterozygosity (151 data points) and mitochondrial haplotype diversity (201 data points). We used linear regressions to link genetic diversity and 11 ecological traits. We also tested for spatial autocorrelation and trends in the residuals. ResultsAmong-species variation in microsatellite heterozygosity was explained by three ecological traits: vertical distribution, migration type and body length. Variation in mitochondrial haplotype diversity was also explained by vertical distribution and migration type, and by reproductive strategy (semelparity). However, vertical distribution and migration type showed opposite effects on microsatellites and mitochondrial diversity. After accounting for the effects of ecological traits, no spatial pattern was detected, except for one of the species considered. Main conclusionsEcological factors explain an important proportion of the among-species genetic diversity. These results suggest that life history strategies of the species influence the variation of microsatellite diversity indirectly through their effect on effective population size, while the spatial variations of genetic diversity seem to be too complex to be identified in our analysis. We found very different effects of traits on mitochondrial and nuclear DNA diversity, which can be explained by the specificities of mitochondrial DNA (absence of recombination, maternal inheritance and non-neutrality).
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