Dolphins of the kelp: Data priorities for Falkland's inshore cetaceans

Dr Marina Costa

Background

The Falklands near-shore waters host a unique community of Commerson’s (Cephalorhynchus commersonii - Picture 1) and Peale’s (Lagenorhynchus australis) dolphins that exhibit a sympatric co-occurrence and apparent year-round reliance on coastal kelp forests. Despite both species being recognised as of conservation concern under international, regional and national plans relatively little is known about their populations or biology and hence vulnerability to anthropogenic threats.

Commerson Dolphin spotted near the shore at the north coast of Cape Pembroke in October 2016

Whilst offshore surveys have been conducted by Joint Nature Conservation Committee, inshore studies has been limited to voluntary cetacean reporting, cataloguing of historical strandings and the small-scale Darwin Challenge pilot study that is the genesis of this project. This lack of data on which to base management decisions has been recognised as a major threat to effective conservation and restricts inclusion into on-going national spatial planning initiatives and inshore ecosystem-based fisheries assessments.

Project aim

The aim of the Dolphins of the kelp project is to establish baseline data on the abundance, distribution, natural history and genetic diversity of the Falklands inshore cetacean populations to provide a scientific basis for conservation and ecosystem-based marine management initiatives.

In addition to the scientific work packages, this project has a core stakeholder engagement component, and the Project Manager will work with, and engage a wide range of stakeholders in addition to regular liaison with project partners.

The project begun in mid-2016, is operative since the last 20th of October 2016 and it is expected to last until September 2018

Funders and partners

The project is funded by Darwin Plus (www.darwininitiative.org.uk) and is being delivered by SAERI in collaboration with the Falkland Islands Government and 6 partner organisations: Premier Oil, Falklands Conservation, Austral Biodiversity Ltd, Shallow Marine Surveys Group (SMSG), Oregon State University and University of St. Andrews.

Methods

The project prioritises biological aspects of greatest conservation relevance, whilst considering the data needs of parallel marine management initiatives. The project will be delivered through the following complimentary work programmes.

  1. Island-Wide Transect Survey

A line-transect survey utilising distance sampling methodologies (Picture 2) will provide abundance estimates and map distribution island-wide for all inshore cetacean species within 10km from shore. Environmental covariates will be collected to permit a model-based assessment of abundance and to investigate drivers of distribution under scenarios of future change and within marine spatial modelling. The population and distribution data will place focal studies into perspective and allow representative sites to be selected for focal study into aspects of the biology and ecology.

Observers onboard the vessel Condor during the pilot surveys carried out in 2014

  1. Focal study Repeat Transect Sampling

Focal studies in three areas will utilise repeat transect sampling with closing mode for photo-identification. Resource utilisation in winter and summer will be investigated through: the degree of the dolphins association with specific habitat types; behaviour and activity; and social factors. This will allow investigation of potential drivers of small-scale habitat selection in these sympatric species and highlight critical habitats. Photo-Identification of individual dolphins will provide the means to study their movement patterns, site fidelity, and group social dynamics; whilst mark-recapture methods can estimate the size and survival rates of the population in the focal area. Ranging patterns can suggest the spatial range at which management should be considered, the likelihood of population separation and the vulnerability of the species to localised impacts.

  1. Passive Acoustic Monitoring (PAM)

Static PAM will be deployed at specific sites allowing the temporal occurrence of dolphins to be quantified. The technique is ideally suited to remote harsh environments as data on the presence of dolphins are collected continuously irrespective of short-daylight or weather conditions which can limit visual-surveys. PAM will be used to investigate temporal drivers and potential seasonal patterns in area utilisation with 2 shallow-water units deployed inshore and 4 deep-water units nearshore.

  1. Genetic diversity and local population structure

Genetic sampling will be conducted to investigate genetic diversity and local population structure. This represents the first genetic characterisation of Peale’s and Commerson’s dolphin population within the Falklands. The work will assess the degree of genetic separation from conspecific populations in South America; the genetic diversity around the Falkland Islands, in comparison to other conspecific population and expectations for effective population size; the degree of interchange or isolation among local populations within the Falkland Islands to assess the scale of management units; and level of kinship across generations within groups to better understand population connectivity on an ecological time scale. Skin and blubber samples, collected with a small biopsy dart will be stored and archived to allow subsequent analysis for natural isotope ratios (C/N), pollutant contaminants, etc. in future associated research.

Project Updates