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Planque Y, Spitz J, Authier M, Guillou G, Vincent C, Caurant F. Trophic niche overlap between sympatric harbour seals ( Phoca vitulina) and grey seals ( Halichoerus grypus) at the southern limit of their European range (Eastern English Channel). Ecol Evol 2021; 11:10004-10025. [PMID: 34367555 PMCID: PMC8328439 DOI: 10.1002/ece3.7739] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 05/12/2021] [Accepted: 05/14/2021] [Indexed: 11/30/2022] Open
Abstract
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 variability and interindividual variability. Foraging areas of these individuals were identified from telemetry data. The three independent approaches provided converging results, revealing a high trophic niche overlap due to consumption of benthic flatfish. Two diet clusters were dominated by either small or large benthic flatfish; these comprised 85.5% [CI95%: 80.3%-90.2%] of harbour seal scats and 46.8% [35.1%-58.4%] of grey seal scats. The narrower isotopic niche of harbour seals was nested within that of grey seals (58.2% [22.7%-100%] overlap). Grey seals with isotopic values similar to harbour seals foraged in coastal waters close to the BDS alike harbour seals did, suggesting the niche overlap may be due to individual grey seal strategies. Our findings therefore provide the basis for potential competition between both species (foraging on benthic flatfish close to the BDS). We suggest that a continued increase in seal numbers and/or a decrease in flatfish supply in this area could cause/amplify competitive interactions and have deleterious effects on harbour seal colonies.
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Affiliation(s)
- Yann Planque
- Centre d'Études Biologiques de ChizéCEBC, UMR 7372 CNRS/La Rochelle UniversitéLa RochelleFrance
| | - Jérôme Spitz
- Centre d'Études Biologiques de ChizéCEBC, UMR 7372 CNRS/La Rochelle UniversitéLa RochelleFrance
- Observatoire PelagisUMS 3462 CNRS/La Rochelle UniversitéLa RochelleFrance
| | - Matthieu Authier
- Observatoire PelagisUMS 3462 CNRS/La Rochelle UniversitéLa RochelleFrance
- ADERAPessac CedexFrance
| | - Gaël Guillou
- Littoral Environnement et Sociétés, LIENSsUMR 7266 CNRS/La Rochelle UniversitéLa RochelleFrance
| | - Cécile Vincent
- Centre d'Études Biologiques de ChizéCEBC, UMR 7372 CNRS/La Rochelle UniversitéLa RochelleFrance
| | - Florence Caurant
- Centre d'Études Biologiques de ChizéCEBC, UMR 7372 CNRS/La Rochelle UniversitéLa RochelleFrance
- Observatoire PelagisUMS 3462 CNRS/La Rochelle UniversitéLa RochelleFrance
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Hays GC, Laloë J, Rattray A, Esteban N. Why do Argos satellite tags stop relaying data? Ecol Evol 2021; 11:7093-7101. [PMID: 34141278 PMCID: PMC8207149 DOI: 10.1002/ece3.7558] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 03/17/2021] [Accepted: 03/22/2021] [Indexed: 11/18/2022] Open
Abstract
Satellite tracking of animals is very widespread across a range of marine, freshwater, and terrestrial taxa. Despite the high cost of tags and the advantages of long deployments, the reasons why tracking data from tags stop being received are rarely considered, but possibilities include shedding of the tag, damage to the tag (e.g., the aerial), biofouling, battery exhaustion, or animal mortality.We show how information relayed via satellite tags can be used to assess why tracking data stop being received. As a case study to illustrate general approaches that are broadly applicable across taxa, we examined data from Fastloc-GPS Argos tags deployed between 2012 and 2019 on 78 sea turtles of two species, the green turtle (Chelonia mydas) and the hawksbill turtle (Eretmochelys imbricata).Tags transmitted for a mean of 267 days (SD = 113 days, range: 26-687 days, median = 251 days). In 68 of 78 (87%) cases, battery failure was implicated as the reason why tracking data stopped being received. Some biofouling of the saltwater switches, which synchronize transmissions with surfacing, was evident in a few tags but never appeared to be the reason that data reception ceased.Objectively assessing why tags fail will direct improvements to tag design, setup, and deployment regardless of the study taxa. Assessing why satellite tags stop transmitting will also inform on the fate of tagged animals, for example, whether they are alive or dead at the end of the study, which may allow improved estimates of survival rates.
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Affiliation(s)
- Graeme C. Hays
- School of Life and Environmental SciencesDeakin UniversityGeelongVic.Australia
| | | | - Alex Rattray
- School of Life and Environmental SciencesDeakin UniversityGeelongVic.Australia
| | - Nicole Esteban
- Faculty of Science and EngineeringSwansea UniversitySwanseaUK
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Henderson AF, McMahon CR, Harcourt R, Guinet C, Picard B, Wotherspoon S, Hindell MA. Inferring Variation in Southern Elephant Seal At-Sea Mortality by Modelling Tag Failure. FRONTIERS IN MARINE SCIENCE 2020; 7. [PMID: 0 DOI: 10.3389/fmars.2020.517901] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Carroll EL, Hall A, Olsen MT, Onoufriou AB, Gaggiotti OE, Russell DJ. Perturbation drives changing metapopulation dynamics in a top marine predator. Proc Biol Sci 2020; 287:20200318. [PMID: 32486973 DOI: 10.1098/rspb.2020.0318] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Metapopulation theory assumes a balance between local decays/extinctions and local growth/new colonisations. Here we investigate whether recent population declines across part of the UK harbour seal range represent normal metapopulation dynamics or are indicative of perturbations potentially threatening the metapopulation viability, using 20 years of population trends, location tracking data (n = 380), and UK-wide, multi-generational population genetic data (n = 269). First, we use microsatellite data to show that two genetic groups previously identified are distinct metapopulations: northern and southern. Then, we characterize the northern metapopulation dynamics in two different periods, before and after the start of regional declines (pre-/peri-perturbation). We identify source-sink dynamics across the northern metapopulation, with two putative source populations apparently supporting three likely sink populations, and a recent metapopulation-wide disruption of migration coincident with the perturbation. The northern metapopulation appears to be in decay, highlighting that changes in local populations can lead to radical alterations in the overall metapopulation's persistence and dynamics.
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Affiliation(s)
- Emma L Carroll
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand.,Scottish Oceans Institute and School of Biology, University of St Andrews, St Andrews, UK.,Sea Mammal Research Unit, University of St Andrews, St Andrews, UK
| | - Ailsa Hall
- Sea Mammal Research Unit, University of St Andrews, St Andrews, UK
| | - Morten Tange Olsen
- Section for Evolutionary Genomics, GLOBE Institute, University of Copenhagen, Denmark
| | - Aubrie B Onoufriou
- Scottish Oceans Institute and School of Biology, University of St Andrews, St Andrews, UK
| | - Oscar E Gaggiotti
- Scottish Oceans Institute and School of Biology, University of St Andrews, St Andrews, UK
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Johnston DW, Frungillo J, Smith A, Moore K, Sharp B, Schuh J, Read AJ. Trends in Stranding and By-Catch Rates of Gray and Harbor Seals along the Northeastern Coast of the United States: Evidence of Divergence in the Abundance of Two Sympatric Phocid Species? PLoS One 2015. [PMID: 26200461 PMCID: PMC4511798 DOI: 10.1371/journal.pone.0131660] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Harbor seals and gray seals are sympatric phocid pinnipeds found in coastal waters of the temperate and sub-Arctic North Atlantic. In the Northwest Atlantic, both species were depleted through a combination of subsistence hunts and government supported bounties, and are now re-occupying substantial portions of their original ranges. While both species appear to have recovered during the past 2 decades, our understanding of their population dynamics in US waters is incomplete. Here we describe trends in stranding and bycatch rates of harbor and gray seals in the North East United States (NEUS) over the past 16 years through an exploratory curve-fitting exercise and structural break-point analysis. Variability in gray seal strandings in Southern New England and bycatch in the Northeast Sink Gillnet Fishery were best described by fitting positive exponential and linear models, and exhibited rates of increase as high as 22%. In contrast, neither linear nor exponential models fit the oscillation of harbor seal strandings and bycatch over the study period. However, a breakpoint Chow test revealed that harbor seal strandings in the Cape Cod, Massachusetts region and harbor seal bycatch in the Northeast Sink Gillnet Fishery increased in the 1990s and then started declining in the early to mid-2000s. Our analysis indicates that ongoing variation in natural and anthropogenic mortality rates of harbor and gray seals in the NEUS is not synchronous, and likely represents diverging trends in abundance of these species as they assume new roles in the marine ecosystems of the region.
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Affiliation(s)
- David W. Johnston
- Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University of Marine Laboratory, 135 Duke Marine Lab Rd., Beaufort, NC, 28516, United States of America
- * E-mail:
| | - Jaime Frungillo
- Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University of Marine Laboratory, 135 Duke Marine Lab Rd., Beaufort, NC, 28516, United States of America
| | - Ainsley Smith
- Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University of Marine Laboratory, 135 Duke Marine Lab Rd., Beaufort, NC, 28516, United States of America
- Integrated Statistics, 16 Sumner Street, Woods Hole, MA, 02543, United States of America
| | - Katie Moore
- International Fund for Animal Welfare, Marine Mammal Rescue and Research Program, 290 Summer St., Yarmouth Port, MA, 02675, United States of America
| | - Brian Sharp
- International Fund for Animal Welfare, Marine Mammal Rescue and Research Program, 290 Summer St., Yarmouth Port, MA, 02675, United States of America
| | - Janelle Schuh
- Animal Rescue Program, Sea Research Foundation, 55 Coogan Blvd., Mystic, CT, 06355-1997, United States of America
| | - Andrew J. Read
- Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University of Marine Laboratory, 135 Duke Marine Lab Rd., Beaufort, NC, 28516, United States of America
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