Delayed response to environmental conditions and infra-seasonal dynamics of the short-beaked common dolphin distribution

Date 2022
Temporal extent 2020-01-01 -2021-04-15
Author(s) Lambert CharlotteORCID1, 2, Authier MatthieuORCID1, Blanchard Ariane1, Dorémus GhislainORCID1, Laran SophieORCID1, Van Canneyt Olivier1, Spitz JérômeORCID1, 2
Affiliation(s) 1 : CNRS - La Rochelle Université, UAR 3462, Observatoire Pelagis, F-17000 La Rochelle, France
2 : CNRS - La Rochelle Université, UMR 7372, Centre d’Etudes Biologiques de Chizé, F-79360 Villiers-en-bois, France
DOI 10.17882/86805
Publisher SEANOE
Keyword(s) Common dolphins, Bay of Biscay, Winter, Simulation, Temporal lag, Dynamic species distribution modelling
Abstract

Cetaceans adjust their distribution and abundance to encountered conditions across years and seasons, but we poorly understand such small-scale changes for many species, especially in winter. Crucial challenges yet weight on some populations during this season, such as the high levels of fisheries-induced mortality faced by the common dolphin (Delphinus delphis) in the North-East Atlantic shelves. For such species, comprehend the winter fine-scale dynamics is crucial. We aimed at identifying the dolphin distribution drivers within the winters 2020 and 2021, with a focus on determining the lag between changes in oceanographic conditions and in dolphin distribution. They were related with temporal delays specific to the nature and the cascading effects oceanographic processes had on the trophic chain. By determining the most important conditions and lags to dolphin distributions, we shed light on the yet poorly understood intrusions of dolphins within coastal waters during winter: they displayed a strong preference for the coastal-shelf waters front and extensively followed its spatial variations, their overall densities increasing over the period and peaking in March-April. The results presented here provided invaluable information on the winter distribution dynamics and should inform management decisions to help reducing the unsustainable mortalities of this species in fisheries by-catch.

Licence CC-BY-NC-SA
Utilisation This work is based on three aerial surveys conducted in the Bay of Biscay in the winters 2020 and 2021: SPEE, CAPECET and SAMM II surveys, conducted by Observatoire Pelagis UAR 3462 CNRS-LRUniv.
Acknowledgements This work was funded by the Office Français de la Biodiversité - Parc naturel marin de l'estuaire de la Gironde et de la mer des Pertuis (Gironde Estuary and Pertuis Sea Marine Nature Park; https://plan-gestion.parc-marin-gironde-pertuis.fr/) and the Région Nouvelle Aquitaine (contract AFB/2018/369 and contract OFB/20/0634), with support from the French Ministry in charge of the Environment.
Sensor metadata

Archive of analysis code used in Lambert et al. 2022 Delayed response to environmental conditions and infra-seasonal dynamics of the short-beaked common dolphin distribution, RSOS.

This repository contains all data and codes necessary to replicate the analyses and results presented in the paper. It is organised as follows:

  • functions: the folder contains all the functions necessary for running the R scripts.
  • data: 
    • Map files: land and isobath files used in the codes
    • Surveys files: there is two files for each surveys, one for the effort (5km-long segments) and one for the observations
    • Variables: raster stacks of all environmental conditions considered and used in the analyses.
  • scripts : the folder contains the nine scripts to run all the analyses described in the paper. Titles are self-explanatory.
  • scripts results: this folder is empty for now, but is to be populated when running the codes.
Data
File Size Format Processing Access
158 MB zip archive Processed data Access on demand until 2023-12-31
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How to cite 

Lambert Charlotte, Authier Matthieu, Blanchard Ariane, Dorémus Ghislain, Laran Sophie, Van Canneyt Olivier, Spitz Jérôme (2022). Delayed response to environmental conditions and infra-seasonal dynamics of the short-beaked common dolphin distribution. SEANOE. https://doi.org/10.17882/86805