08.05.2019 – Surface action

Our day began on windy seas with an eventful sighting of Bottlenose dolphins (Tursiops truncatus), that socialised amongst one another actively at the surface, entertaining all those on board with impressive leaps and breaches. Our spotter then informed us about a large Fin whale (Balaenoptera physalus) that was travelling west right infant of Calheta. The animal was probably a juvenile and displayed a rather evasive behaviour as it sliced through the surface with its elegant, hydrodynamic body.

Despite the fact that our traditional boat searched far and wide to return without a sighting of cetaceans, a degree of surface action was still there. Currently we have large shoals of Bluefin tuna (Thunnus thynnus) whose speedy hunting behaviour at the surface looks very similar to that of dolphins, often fooling even the eagle eyes of our spotter. Before we make early assumptions, its always safer for our boats to go to the sighting area and investigate whether fish or dolphins are hunting. Observations of bird behaviour often helps to determine this: when predatory fish or sharks are hunting they behave sporadically, sitting calmly at the surface before circling a large area again. This was the case today but, in contrast to most sightings involving tuna, these animals were clearly visible at the surface as they surged in group formation after their prey.

We also encountered several Portuguese Man O’Wars (Physalia physalis) that were carried by the wind and waves to our shores, providing a good feast to basking Loggerhead turtles (Caretta caretta) and to Oceanic sunfish (Mola mola). One of my guests asked me how old these Siphonophores get, a question I honestly did not know the answer to! But some quick research soon showed that this is almost entirely up to the winds and currents these zooid colonies are subject to. Apparently the average lifespan of the colony is 1 year, with these organisms often occurring in small groups known collectively as legions.

By Paula Thake

Sightings of the day

Ribeira Brava

14:30 No sighting

Stenella

10:00 Bottlenose dolphins, Fin whales