New publication: Identifying the relevant local population for environmental impact assessments of mobile marine fauna

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We are pleased to announce the following publication in Frontiers in Marine Science (Marine Affairs and Policy):

Identifying the Relevant Local Population for Environmental Impact Assessments of Mobile Marine Fauna

Full citation: Chabanne, D.B.H., Finn, H. and Bejder, L. (2017). Identifying the Relevant Local Population for Environmental Impact Assessments of Mobile Marine Fauna. Frontiers in Marine Science, 4: 148. DOI: 10.3389/fmars.2017.00148



Environmental impact assessments must be addressed at a scale that reflects the biological organization for the species affected. It can be challenging to identify the relevant local wildlife population for impact assessment for those species that are continuously distributed and highly mobile. Here, we document the existence of local communities of Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabiting coastal and estuarine waters of Perth, Western Australia, where major coastal developments have been undertaken or are proposed (Figure 1). Using sighting histories from a 4-year photo-identification study, we investigated fine-scale, social community structure of dolphins based on measures of social affinity, and network (Half-Weight Index—HWI, preferred dyadic association tests, and Lagged Association Rates—LAR), home ranges, residency patterns (Lagged Identification Rates—LIR), and genetic relatedness. Analyses revealed four socially and spatially distinct, mixed-sex communities. The four communities (Figures 2 and 3) had distinctive social patterns varying in strength, site fidelity, and residency patterns. Overlap in home ranges and relatedness explained little to none of the association patterns between individuals, suggesting complex local social structures. The study demonstrated that environmental impact assessments for mobile, continuously distributed species must evaluate impacts in light of local population structure, especially where proposed developments may affect core habitats of resident communities or sub-populations. Here, the risk of local extinction is particularly significant for an estuarine community because of its small size, limited connectivity with adjacent communities, and use of areas subject to intensive human use. In the absence of information about fine-scale population structure, impact assessments may fail to consider the appropriate biological context.

CEDP_Study area

Figure 1. Maps of the study area showing: (A) the transect routes per geographic regions (GR, Gage Roads; SCR, Swan Canning Riverpark; OA, Owen Anchorage; CS, Cockburn Sound) with locations of past, current, and proposed developments (1- pile driving; 2- dredging; 3- desalination; 4- outer harbor); and (B) the bathymetry (in meters) with the locations of the groups sighted during the systematic surveys conducted from 2011 to 2015, including mixed groups (i.e., mix of individuals from different communities).

Network diagram for 129 bottlenose dolphins using the HWI

Figure 2. Network diagram for 129 bottlenose dolphins using the HWI. The shape of each node indicates its sex (circle: females; square: males; triangle; unsexed), and the color of each node indicates its unit defined by the modularity of Newman (2006) (purple ComA; red ComB; green ComC; yellow and orange sub-communities D and D’), although three individuals were assigned to two different units depending on the method (Newman vs. Hierarchical linkage). Only links representing affiliations (HWI > 0.16) are shown, and link width is proportional to index weight. Node size is based on the betweenness centrality measure of each individual.

Bathymetry and core areas of dolphins in PerthFigure 3.  Study area showing the bathymetry and core areas (a) based on the 50% kernel density and home ranges (b) based on the 95% kernel density estimated for each community using clustered individual sightings. Communities are: ComA-purple; ComB-red; ComC-green; and ComD-yellow. Bathymetry data were provided by the Department of Transport, Western Australia.


Download the paper: The article can be downloaded HERE, or alternatively, please email Delphine Chabanne for a PDF at


Project Funding:
For financial, technical and logistical support, we thank the Swan River Trust, Fremantle Ports and Fremantle Sailing Club. We also thank the Department of Transport (Western Australia) for providing bathymetry data. Field research was conducted under the conditions of licenses, authorities and permits from the Western Australia Department of Parks and Wildlife (permit numbers SF008067, SF008682, SF009286 and SF009874) and the Murdoch University Animal Ethics Committee (permit numbers W2342/10 and R2649/14).


For further information on the Coastal and Estuarine Dolphin Project and Indo-Pacific bottlenose dolphins in Perth metropolitan waters, see also following papers:

Chabanne, D.B.H., Pollock, K.H., Finn, H. and Bejder, L. 2017 Applying the Multistate Capture-recapture Robust Design to characterize metapopulation structure. Methods in Ecology and Evolution. doi: 10.1111/2041-210X.12792

Chabanne, D., Finn, H., Salgado-Kent, C., and Bejder, L. (2012). Identification of a resident community of bottlenose dolphins (Tursiops aduncus) in the Swan Canning Riverpark, Western Australia, using behavioural information. Pacific Conservation Biology 18, 247-262. doi:  10.1071/PC120247

Donaldson, R., Finn, H., Bejder, L., Lusseau, D., and Calver, M. (2012a). Response: social learning of risky behaviour: importance for impact assessments, conservation and management of human–wildlife interactions. Animal Conservation 15, 442-444. doi: 10.1111/j.1469-1795.2012.00601.x

Donaldson, R., Finn, H., Bejder, L., Lusseau, D., and Calver, M. (2012b). The social side of human-wildlife interaction: wildlife can learn harmful behaviours from each other. Animal Conservation 15, 427-435. doi: 10.1111/j.1469-1795.2012.00548.x

Donaldson, R., Finn, H., and Calver, M. (2010). Illegal feeding increases risk of boat-strike and entanglement in bottlenose dolphins in Perth, Western Australia. Pacific Conservation Biology 16, 157-161. doi: 10.1071/PC100157

Finn, H., Donalson, R., and Calver, M. (2008). Feeding Flipper: a case study of a human-dolphin interaction. Pacific Conservation Biology 14, 215-225. doi: 10.1071/PC080215

Stephens, N., Duignan, P.J., Wang, J., Bingham, J., Finn, H., Bejder, L., et al. (2014). Cetacean morbillivirus in coastal Indo-Pacific bottlenose dolphins, Western Australia. Emerging Infectious Disease Journal 20, 666-670. doi:  10.3201/eid2004.131714

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