Focal study

The focal study consists of a series of boat-based surveys carried out twice a year (during winter and summer) in three locations to collect photo-identification (link below)  data and, in one location, acoustic data (link below).

Study area

The three areas for the focal studies have been selected based on their accessibility and potential presence of target species. The areas are:

A. Port Stanley – Port Williams – Berkeley Sound (East Falkland)

B. Choiseul Sound (East Falkland)

C. Port Howard – Swan Island – Many Branch (West Falkland)

 

Platform

Cetacean observation is carried out using the rigid-hulled inflatable boat (RHIB) “Baltic Warrior” owned by the Shallow Marine Surveys Group (http://www.smsg-falklands.org). The skipper is Steve Cartwright.

 

Photo-identification Methods

Observation is carried out by two observers at a speed ranging from 13 km/h to 22 km/h (from 7 to 12 knots). When a sighting occurs navigation is temporally suspended and animals are approached to estimate group size and age composition and to collect photo-identification data. Pictures are taken by the two researchers using a Canon EOS 7D Mark II, equipped with a lens EF 70-200mm f/2.8, and a Nikon D7200, equipped with a lens AF-S VR-NIKKOR 70-200mm 1:2.8G. Underwater video are taken using a GOPRO Hero 4.

Observers searching for cetaceans during the focal study.

 

Researcher attempting to take pictures of the dorsal fin of every individual in the group.

Identification pictures are taken focusing on the notches and nicks present on the dorsal fin of the individuals. Scratches, wounds, scars, pigmentation and fin shapes are also used to facilitate individual identification (see protocol).

a) Commerson’s Dolphin

b) Peale's Dolphin

Dorsal fins of a. Commerson’s and b. Peale’s dolphins showing notches, nicks and scars used in the identification of individuals. Photos by Marina Costa - SAERI.

 

Photo-identification techniques allow the “capture” and “recapture” of marked individuals without physical handling. These mark-recaptures methods use the combination of multiple recapture occasions to estimate demographic parameters of the population such as abundance, survival probability, growth and recruitment rates, residency and movement patterns.

For the data collection protocol used, see HERE.

Passive Acoustic Monitoring (PAM) Methods

Static PAMs are used to investigate the temporal occurrence of dolphins in one area. 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. Five units PAM will be used to investigate temporal drivers and potential seasonal patterns in space utilisation of Many Branch Harbour. The C-PODs will collect data for 16 months; every 3-4 months data are downloaded and batteries changed.

Preliminary results

The first survey has been carried out in the summer of 2016 (November and December) in the three selected areas, during eleven days of survey at sea. Furthermore, during the survey carried out in January 2017 to collect dolphin tissue for the genetic analyses (see below 3 - Genetic diversity and local population structure) other data were added, resulting in a total of:

  • 20 days spent at sea.
  • About 766 km navigated searching for dolphin.
  • 169 sightings made, of which 132 of Commerson’s dolphins, 36 of Peale’s dolphins and one of orcas.
  • 14,024 pictures taken, of which 12,204 of Commerson’s dolphins and 1,675 of Peale’s dolphins and 145 of orcas.

Map showing the effort during the first focal study carried out in November and December 2016 and the genetic survey carried out in January 2017. Area A: Port Stanley – Port Williams – Berkeley Sound (East Falkland); Area B: Choiseul Sound (East Falkland); Area C: Port Howard – Swan Island – Many Branch (West Falkland). Sighting positions of Commerson’s (red triangle) and Peale’s (green circle) dolphins are shown.

The analysis of the pictures is in progress for Commerson’s dolphins and has been concluded for the Peale’s dolphins, resulting in 36 individuals identified (9 with very distinctive marks and 27 with poor markings) of which 13 individuals (36%) have been recaptured.

For the catalogue of marked Peale’s dolphins, see HERE.

The C-PODs have been deployed in Many Branch on the 16th of April 2017. The first set of data will be downloaded in July 2017.