Papers by Matthieu Authier
Frontiers in Marine Science, Jun 12, 2023
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Frontiers in Marine Science
Marine megafauna plays an important functional role in marine ecosystems as top predators but are... more Marine megafauna plays an important functional role in marine ecosystems as top predators but are threatened by a wide range of anthropogenic activities. Bycatch, the incidental capture of non-targeted species in commercial and recreational fisheries, is of particular concern for small cetacean species, such as dolphins and porpoises. In the North-East Atlantic, common dolphin (Delphinus delphis, Linné 1758) bycatch has been increasing and associated with large numbers of animals stranding during winter on the French Atlantic seashore since at least 2017. However, uncertainties around the true magnitude of common dolphin bycatch and the fisheries involved have led to delays in the implementation of mitigation measures. Current data collection on dolphin bycatch in France is with non-dedicated observers deployed on vessels for the purpose of national fisheries sampling programmes. These data cannot be assumed representative of the whole fisheries' bycatch events. This feature mak...
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Royal Society Open Science, Nov 1, 2022
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Ecology Letters
Temporal correlations among demographic parameters can strongly influence population dynamics. Ou... more Temporal correlations among demographic parameters can strongly influence population dynamics. Our empirical knowledge, however, is very limited regarding the direction and the magnitude of these correlations and how they vary among demographic parameters and species’ life histories. Here, we use long‐term demographic data from 15 bird and mammal species with contrasting pace of life to quantify correlation patterns among five key demographic parameters: juvenile and adult survival, reproductive probability, reproductive success and productivity. Correlations among demographic parameters were ubiquitous, more frequently positive than negative, but strongly differed across species. Correlations did not markedly change along the slow‐fast continuum of life histories, suggesting that they were more strongly driven by ecological than evolutionary factors. As positive temporal demographic correlations decrease the mean of the long‐run population growth rate, the common practice of ignori...
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Regional Studies in Marine Science
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PLOS ONE, 2022
In the context of wildlife population declines, increasing computer power over the last 20 years ... more In the context of wildlife population declines, increasing computer power over the last 20 years allowed wildlife managers to apply advanced statistical techniques that has improved population size estimates. However, respecting the assumptions of the models that consider the probability of detection, such asN-mixture models, requires the implementation of a rigorous monitoring protocol with several replicate survey occasions and no double counting that are hardly adaptable to field conditions. When the logistical, economic and ecological constraints are too strong to meet model assumptions, it may be possible to combine data from independent surveys into the modelling framework in order to understand population dynamics more reliably. Here, we present a state-space model with an error process modelled on the log scale to evaluate wintering waterfowl numbers in the Camargue, southern France, while taking a conditional probability of detection into consideration. Conditional probabil...
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The published data are the necessary data to redo the analysis used in the targeted publication. ... more The published data are the necessary data to redo the analysis used in the targeted publication. For each species, the data are the three-day maximal number of stranded individuals for each month and over the period from 1990 to 2016 (for the short-beaked common dolphin and the striped dolphin) or the period from 1997 to 2016 (for the harbour porpoise). Please refer to the targeted publication and the Supporting Information
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Frontiers in Marine Science, 2021
Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is ... more Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is one of the main causes of mortality of marine mammals worldwide. When quantitative conservation objectives and management goals are clearly defined, computer-based procedures can be used to explore likely population dynamics under different management scenarios and estimate the levels of anthropogenic removals, including bycatch, that marine mammal populations may withstand. Two control rules for setting removal limits are the Potential Biological Removal (PBR) established under the US Marine Mammal Protection Act and the Removals Limit Algorithm (RLA) inspired from the Catch Limit Algorithm (CLA) developed under the Revised Management Procedure of the International Whaling Commission. The PBR and RLA control rules were tested in a Management Strategy Evaluation (MSE) framework. A key feature of PBR and RLA is to ensure conservation objectives are met in the face of the multiple uncertai...
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bioRxiv, 2020
Intense development of Offshore Wind Farms (OFWs) has occurred in the North Sea with several more... more Intense development of Offshore Wind Farms (OFWs) has occurred in the North Sea with several more farms planned for the near future. These OFWs pose a threat to marine megafauna stressing the need to mitigate the impact of human activities. To help mitigating impacts, the Before After Gradient (BAG) design was proposed. We thus explored the use of the BAG method on megafauna sightings recorded at different distances from wind farms in the southern North Sea. We predicted intra-annual variability in species distribution, then correlated species distribution with the presence of operational OFWs and investigated the potential impact the operation of prospective OFWs may have on species distribution. Three patterns of intra-annual variability were predicted: species present most abundantly in spring, in winter or all year-round. We recommend that future OFW constructions be planned in summer and early fall to minimise impact on cetaceans and that offshore areas off northern France and ...
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Bycatches appear to be one of the main causes of man-induced mortality of dolphins and porpoises ... more Bycatches appear to be one of the main causes of man-induced mortality of dolphins and porpoises in the Bay of Biscay. However bycatch estimations for common dolphins vary between 550 (observer-based estimate) and 4700 (stranding-based estimate) per year in the area depending on the methodological choice. In addition to problematic monitoring, mitigation measures as the use of pingers have been inefficient in French waters. Consequently, improving the understanding of interactions between small cetaceans and fisheries remains a challenge. This paper describes how divergent scientific estimations of cetacean bycatches can affect interactions between stakeholders. By using the Actor-Network Theory, we focused on scientific and managerial instruments translating small cetacean bycatches in the Bay of Biscay. According to this social science perspective, instruments are not neutral and play a central role in defining how stakeholders look at an issue. Translating observations into an ag...
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Changes in the foraging environment and at-sea distribution of southern elephant seals from Kergu... more Changes in the foraging environment and at-sea distribution of southern elephant seals from Kerguelen Islands were investigated over a decade (2004–2018) using tracking, weaning mass and blood δ<sup>13</sup>C values. Females showed either a sub-Antarctic or an Antarctic foraging strategy, and no significant shift in their at-sea distribution was detected between 2004 and 2017. The proportion of females foraging in sub-Antarctic versus Antarctic habitats did not change over the 2006–2018 period. Pup weaning mass varied according to the foraging habitat of their mothers. The weaning mass of sub-Antarctic foraging mothers' pups decreased by 11.7 kg over the study period, but they were on average 5.8 kg heavier than pups from Antarctic foraging mothers. Pup blood δ<sup>13</sup>C values decreased by 1.1‰ over the study period regardless of their sex and the presumed foraging habitat of their mothers. Together, these results suggest an ecological change is occurring within the Indian sector of the Southern Ocean with possible consequences on the foraging performance of southern elephant seals. We hypothesize that this shift in δ<sup>13</sup>C is related to a change in primary production and/or in the composition of phytoplankton communities, but this requires further multidisciplinary investigations.
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Frontiers in Marine Science, 2021
Bycatch, the non-intentional capture or killing of non-target species in commercial or recreation... more Bycatch, the non-intentional capture or killing of non-target species in commercial or recreational fisheries, is a world wide threat to protected, endangered or threatened species (PETS) of marine megafauna. Obtaining accurate bycatch estimates of PETS is challenging: the only data available may come from non-dedicated schemes, and may not be representative of the whole fisheries effort. We investigated, with simulated data, a model-based approach for estimating PETS bycatch from non-representative samples. We leveraged recent development in the statistical analysis of surveys, namely regularized multilevel regression with post-stratification, to infer total bycatch under realistic scenarios of data sampling such as under-sampling or over-sampling when PETS bycatch risk is high. Post-stratification is a survey technique to re-align the sample with the population and addresses the problem of non-representative samples. Post-stratification requires to sub-divide a population of inter...
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Frontiers in Marine Science, 2021
The first Unusual Mortality Event (UME) related to fishing activity along the Atlantic coast reco... more The first Unusual Mortality Event (UME) related to fishing activity along the Atlantic coast recorded by the French Stranding Network was in 1989: 697 small delphinids, mostly common dolphins, washed ashore, most of them with evidence of having been bycaught. Since then, UMEs of common dolphins have been observed nearly every year in the Bay of Biscay; unprecedented records were broken every year since 2016. The low and unequally distributed observation efforts aboard fishing vessels in the Bay of Biscay, as well as the lack of data on foreign fisheries necessitated the use of complementary data (such as stranding data) to elucidate the involvement of fisheries in dolphin bycatch. The aim of this work was to identify positive spatial and temporal correlations between the likely origins of bycaught stranded common dolphins (estimated from a mechanistic drift model) and fishing effort statistics inferred from Vessel Monitoring System (VMS) data on vessels >12 m long. Fisheries whos...
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Methods in Ecology and Evolution, 2021
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Ecology and Evolution, 2021
Sympatric harbour (Phoca vitulina) and grey seals (Halichoerus grypus) are increasingly considere... more Sympatric harbour (Phoca vitulina) and grey seals (Halichoerus grypus) are increasingly considered potential competitors, especially since recent local declines in harbour seal numbers while grey seal numbers remained stable or increased at their European core distributions. A better understanding of the interactions between these species is critical for conservation efforts. This study aimed to identify the trophic niche overlap between harbour and grey seals at the southern limit of their European range, in the Baie de Somme (BDS, Eastern English Channel, France), where numbers of resident harbour seals and visiting grey seals are increasing exponentially. Dietary overlap was identified from scat contents using hierarchical clustering. Isotopic niche overlap was quantified using δ13C and δ15N isotopic values from whiskers of 18 individuals, by estimating isotopic standard ellipses with a novel hierarchical model developed in a Bayesian framework to consider both intraindividual va...
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Papers by Matthieu Authier