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Banco de Galicia - September Campaign - CEMMA

CEMMA observers team and Anxuela crew ©CEMMA

Between September 20th and September 28th, the CEMMA team, made up of eight biologists/oceanographers, carried out an expedition to the Banco de Galicia. On board the Anxuela longliner, under the command of skipper Eduardo Mínguez, data and acoustic information was gathered on cetaceans, and a sampling of seabirds was taken by SEO/BirdLife observer Marcel Gil.

The same parallel transects used on the first Banco de Galicia expedition were used on this one. The transects cut as perpendicularly as possible through the bathymetry lines, thereby providing homogeneous coverage for the area under study.

Three-person shifts were established for observing the cetaceans, one at port, another at starboard, and another at the bow of the vessel. Also, a fourth person on an elevated observation point was in charge of both observing cetaceans and recording certain parameters. Observation was done within a 90º field of vision both at port and at starboard.

An acoustic sampling was also taken using a trawl hydrophone, thereby enabling continuous recording and listening in real time to the sounds recorded. When there is a sighting, the observers note down the time and species on a specific acoustic sheet once they reach port. They download the acoustic files recorded and make note of the “acoustic sightings” done at sea. Subsequently, the sightings observed are to be compared with the acoustic recordings.

Poor weather and a rough sea led observation time to be curtailed and bow observation to be eliminated on various occasions. Two of the tracks had to be repeated due to the poor conditions  during the sampling.

In the Banco de Galicia, a total of 25 cetacean sightings included identification of the following species: common rorqual (Balaenoptera physalus), striped dolphin (Stenella coeruleoalba), bottlenose dolphin (Tursiops truncatus), long finned pilot whale (Globicephala melas), and Curvier’s goose-beaked whale (Ziphius cavirostris). In several sightings, the species observed could not be identified.

This year’s expedition had two sightings of striped dolphin young, while no common rorqual young were sighted.

Acoustic recordings were obtained from certain sightings not only of both the delphinae, including recordings of whistling, clicks, and so forth, but also of sperm whales, which were not detected visually.

Acoustic monitoring ©CEMMA
A: rorcual común (Balaenoptera physalus). B: delfín común (Tursiops truncatus). C:delfín listado (Stenella coeruleoalba). D: zifio de Cuvier (Ziphius cavirostris) ©CEMMA