Observations of whales, dolphins and porpoises are greatly affected by both weather and light conditions since you wouldn’t spot anything in a storm or in darkness. To overcome these constraints researchers can opt to listen in for cetaceans instead. Two techniques are regularly used by the IWDG: passive acoustic monitoring (PAM) and static acoustic monitoring (SAM).
PAM uses a hydrophone that is towed behind a research vessel to record vocalisations of whales and dolphins in real time. A computer is monitored which displays a spectrogram of detections that may look like rising lines or dots depending on the species.
SAM consists of a pod attached to the seafloor that records detections of species within the frequency range it is programmed for (low for large whales, high for porpoises and dolphins). When recovered, the downloaded data will display the number of detections made which indicate how important a monitored site is.
Large whales and dolphins have infrequently been biopsied by the IWDG under licence from the National Parks and Wildlife Service since 2000. A specialised dart with a rubber blocker and a hollow tip is fired from a crossbow into the side of a targeted whale or dolphin. The rubber blocker causes the dart to bounce off the animal once it captures a biopsy sample.
Small tips (7 mm in diameter) are used for dolphins while 10 – 30 mm tips are used for whales. If successful, a biopsy dart will have a small sample of skin with blubber attached underneath.
While the technique is invasive, samples collected are used in genetic studies to determine which population animals belong to, an animals establish preferred prey species using stable isotopes, evaluate persistent pollutant levels within their blubber and determine a sampled animals gender which would remain unknown for live animals without this technique.
Is a simple but very effective technique used by the group to trace the movement’s whales and dolphins around Ireland. High quality images taken of an animal’s dorsal fin or tail fluke are collected and then compared to existing image catalogues for that species. Each animal is unique with scars and notches picked up throughout their lifetime that allow researchers to distinguish between individual whales and dolphins.
The technique has been used to identify the presence of resident bottlenose dolphins in the Shannon Estuary and reveal that some Irish humpback whales travel as far north as Iceland and as south as Gibraltar!
Catalogues for bottlenose dolphins, Risso’s dolphins, killer whales, fin and humpback whales are maintained by the IWDG so we would greatly appreciate images to be sent in with your sightings of these species whenever possible.
Surveying at Sea
Research vessels are equipped to venture away offshore into areas where unusual species may occur in Irish waters. IWDG surveyors regularly go to sea on “vessels of opportunity” which might go offshore but are not actively looking for whales or dolphins like dedicated surveys which take place occasionally.
Watches take place during daylight hours using a pair of binoculars to spot animals in the vicinity of the vessel from a suitably high vantage point like a ships bridge. The distance from the animals is estimated and recorded with the species, group size and behaviours seen each time a sighting is made.
Environmental data is also recorded such as wind direction, swell height and sea state which may affect a surveyors ability to spot animals. This type of surveying helps collect data on the distribution and abundance of cetaceans on the high seas.