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 data and, in one location, acoustic data.
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)
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.
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.
Dolphin observers on the rib
Photographing dolphin dorsal fins for identification
commerson's dolphin fin
Peale's dolphin fin
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). The dorsal fins of Commerson’s and Peale’s dolphins (above) show 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.
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:
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.
Image left: Preparing the Peales dolphin catalogue.
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 PAM units 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.
Boat crew deploying C-PODs
Map of C-POD locations
The C-PODs were deployed in Many Branch Harbour on the 16th of April 2017. The first set of data will be downloaded in July 2017.
The project is funded by the Darwin Initiative through the UK Government
