Using large scale surveys to investigate seasonal variations in seabird distribution and abundance. Part II: The Bay of Biscay and the English Channel

Pettex, Emeline; Laran, Sophie; Authier, Matthieu; Blanck, Aurélie; Dorémus, Ghislain; Falchetto, Hélène; Lambert, Charlotte; Monestiez, Pascal; Stéfan, Eric; Canneyt, Olivier Van; Ridoux, Vincent

doi:10.1016/j.dsr2.2016.11.012

“…In the study, the aim was to use datasets containing enough sightings to implement a data-thinning approach in a realistic and meaningful way. To perform the analysis, we used datasets that were previously exploited and described in various publications [ 8 , 9 , 10 , 11 ]. Two taxa with abundant sightings (> 250) and contrasted distributions were selected.…”

Section: Methodsmentioning

confidence: 99%

How many sightings to model rare marine species distributions

Virgili

¹

,

Authier

²

,

Monestiez

³

et al. 2018

Self Cite

View full text Add to dashboard Cite

Despite large efforts, datasets with few sightings are often available for rare species of marine megafauna that typically live at low densities. This paucity of data makes modelling the habitat of these taxa particularly challenging. We tested the predictive performance of different types of species distribution models fitted to decreasing numbers of sightings. Generalised additive models (GAMs) with three different residual distributions and the presence only model MaxEnt were tested on two megafauna case studies differing in both the number of sightings and ecological niches. From a dolphin (277 sightings) and an auk (1,455 sightings) datasets, we simulated rarity with a sighting thinning protocol by random sampling (without replacement) of a decreasing fraction of sightings. Better prediction of the distribution of a rarely sighted species occupying a narrow habitat (auk dataset) was expected compared to the distribution of a rarely sighted species occupying a broad habitat (dolphin dataset). We used the original datasets to set up a baseline model and fitted additional models on fewer sightings but keeping effort constant. Model predictive performance was assessed with mean squared error and area under the curve. Predictions provided by the models fitted to the thinned-out datasets were better than a homogeneous spatial distribution down to a threshold of approximately 30 sightings for a GAM with a Tweedie distribution and approximately 130 sightings for the other models. Thinning the sighting data for the taxon with narrower habitats seemed to be less detrimental to model predictive performance than for the broader habitat taxon. To generate reliable habitat modelling predictions for rarely sighted marine predators, our results suggest (1) using GAMs with a Tweedie distribution with presence-absence data and (2) implementing, as a conservative empirical measure, at least 50 sightings in the models.

show abstract

“…Of course the results presented would benefit from a similar study to be implemented over the rest of the year. Indeed, previous study highlighted seasonal variations of habitat preferences and distribution of cetaceans and seabirds in the Bay of Biscay (Lambert et al, 2017a;Laran et al, 2017;Pettex et al, 2017), showing limited seasonal differences in distribution for bottlenose dolphins and northern fulmars, but large differences in distribution for black-legged kittwakes, auks and northern gannets between summer and winter. The small-sized shearwaters are completely absent from the study region during winter.…”

Section: Discussionmentioning

confidence: 97%

“…The boundaries for Habitats Directive and Bird Directive sites were historically proposed mostly based on expert's knowledge of coastal distributions, with poor information on their temporal variability, and a fortiori on the target species at-sea distributions leading to a succession of small and large sites along the BoB coast, ensuring a good coverage of the auks distribution. The important coverage of bottlenose dolphin distribution (59% of its core area) was largely ensured by the new offshore Habitats Directive site (see Figure 1) that has recently been designated, along with an equivalent Bird Directive site, based on dedicated large-scale surveys (SAMM surveys; Lambert et al, 2017a;Laran et al, 2017;Pettex et al, 2017) within French waters to compensate for the previous absence of any protected sites within offshore waters (Delavenne et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

The persistence in time of distributional patterns in marine megafauna impacts zonal conservation strategies

Lambert

¹

,

eacutemus

²

,

Ridoux

³

2019

Preprint

1

0

View full text Add to dashboard Cite

The main type of zonal conservation approaches corresponds to Marine Protected Areas (MPAs), which are spatially defined and generally static entities aiming at the protection of some target populations by the implementation of a management plan. For highly mobile species the relevance of an MPA over time might be hampered by temporal variations in distributions or home ranges. In the present work, we used habitat model-based predicted distributions of cetaceans and seabirds within the Bay of Biscay from 2004 to 2017 to characterise the aggregation and persistence of mobile species distributional patterns and the relevance of existing MPA network. We explored the relationship between population abundance and spatial extent of distribution to assess the aggregation level of species distribution. Specific core areas of distributions were determined, based on predicted distributions, as the smallest spatial extent including 50% of the population present in the Bay of Biscay and their persistence was calculated over the 14 studied years. The relevance of MPA network was assessed regarding aggregation and persistence. The potential to zonal conservation was confirmed for spatially aggregated and persistent species, as bottlenose dolphins or auks. We showed that aggregation level alone is not sufficient to determine candidates to zonal conservation, since some species might be aggregated in space, but poorly persistent in time (black-legged kittiwake). Nonetheless, some loosely distributed species with strong persistence might not benefit from existing zonal conservation due to poor overlap between existing MPA networks and their core areas of distribution (great skuas). We thus have demonstrated that both aggregation and persistence have potential impact on the amount of spatiotemporal distributional variability encompassed within static MPAs. Our results exemplified the need to have access to a minimal temporal depth in the species distribution data when aiming to designate new site boundaries for the conservation of mobile species.

show abstract

“…The important coverage of bottlenose dolphin distribution (59% of its core area) was largely ensured by the new offshore Habitats Directive site (see Figure 1) that has recently been designated, along with an equivalent Bird Directive site, based on dedicated large-scale surveys (SAMM surveys; Lambert et al, 2017b;Laran et al, 2017;Pettex et al, 2017) within French waters to compensate for the previous absence of any protected sites within offshore waters (Delavenne et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

The importance of spatio-temporal dynamics on MPA's design

Estay¹

2020

PCI Ecology

0

View full text Add to dashboard Cite

The main type of zonal conservation approaches corresponds to Marine Protected Areas (MPAs), which are spatially defined and generally static entities aiming at the protection of some target populations by the implementation of a management plan. For highly mobile species the relevance of an MPA over time might be hampered by temporal variations in distributions or home ranges. In the present work, we used habitat model-based predicted distributions of cetaceans and seabirds within the Bay of Biscay from 2004 to 2017 to characterise the aggregation and persistence of mobile species distributional patterns and the relevance of existing MPA network. We explored the relationship between population abundance and spatial extent of distribution to assess the aggregation level of species distribution. Specific core areas of distributions were determined, based on predicted distributions, as the smallest spatial extent including 50% of the population present in the Bay of Biscay and their persistence was calculated over the 14 studied years. The relevance of MPA network was assessed regarding aggregation and persistence. The potential to zonal conservation was confirmed for spatially aggregated and persistent species, as bottlenose dolphins or auks. We showed that aggregation level alone is not sufficient to determine candidates to zonal conservation, since some species might be aggregated in space, but poorly persistent in time (black-legged kittiwake). Nonetheless, some loosely distributed species with strong persistence might not benefit from existing zonal conservation due to poor overlap between existing MPA networks and their core areas of distribution (great skuas). We thus have demonstrated that both aggregation and persistence have potential impact on the amount of spatiotemporal distributional variability encompassed within static MPAs. Our results exemplified the need to have access to a minimal temporal depth in the species distribution data when aiming to designate new site boundaries for the conservation of mobile species.

show abstract

Using large scale surveys to investigate seasonal variations in seabird distribution and abundance. Part II: The Bay of Biscay and the English Channel

Cited by 29 publications

References 39 publications

How many sightings to model rare marine species distributions

How many sightings to model rare marine species distributions

The persistence in time of distributional patterns in marine megafauna impacts zonal conservation strategies

The importance of spatio-temporal dynamics on MPA's design

Contact Info

Product

Resources

About