11.08.2019 – Squid season

Summertime is the best time to indulge on sun, sea and…squid! August typically marks the beginning of deep-sea squid season here in Madeira, locally known as Potas. The most commonly caught specie is the Orange-back flying squid (Sthenoteuthis pteropus), cephalopods that typically inhabit depths of 200m and, like many other deep-sea organisms, engage in a vertical migration to the surface at nighttime. They may embark on this perilous voyage to feed on the abundant prey trapped in the warmer, upper layers of the the ocean but may also come to shallower waters to spawn, making them a vulnerable catch for fisherman that lure them to their boats at night using artificial light. Local fishermen, however, aren’t the only ones gorging on squid in Madeira’s waters.

Squid serve as an important part of the diet of many marine mammals and serve as an ideal source of hydration since they largely consist of water. Their abundance at this time of the year attracts a diversity of cetaceans along with several other animals, ready to fatten up on this highly nutritious prey. Short-finned pilot whales (Globicephala macrorhynchus) are total squid specialists, with many herds, perhaps even those identified within the resident clans, returning to the islands waters in August in time for squid-season. During the morning tour these gentle cetaceans were seen socialising and logging at the surface, their bullet-shaped bodies fattened with squid, amongst a group of Bottlenose dolphins (Tursiops truncatus) who are just as aware of the Pilot whale’s squid hunting abilities as we are! Our zodiac managed an additional encounter with a large group of charismatic and interactive Atlantic spotted dolphins (Stenella frontalis). The animals came close enough to allow our captain to spot some black ink in their faeces, indicating that they too had fed on some squid.

In the afternoon our Stenella stumbled upon some Blainville’s beaked whales (Mesoplodon densirostris) as we tried to relocate the Pilot whales and Bottlenose dolphins further west. Like most beaked whales, these are suction feeders whose prey pallet mainly consists of cephalopods. While this sighting was rather brief, it was accompanied by an encounter with a Loggerhead turtle (Caretta caretta) and several bird species including the nocturnal Bulwer’s petrel (Bulweira bulwerii) as well as an Arctic Skua (Stercorarius parasiticus) a kleptoparistic bird, ready to snatch prey from others at the surface. 

So in conclusion, squid season provides us with sensational sightings which, unfortunately, come at a large cost for the poor squid that are hunted by a huge variety of predators. Unfair as this may seem, the larger availability of this essential prey may also help the several young calves we saw today, including the tiny newborn pilot whale calf, to become strong, healthy adults.

By Paula Thake

Sightings of the day

Ribeira Brava

10:00 Bottlenose dolphins, Short-finned pilot whales

13:30 Bottlenose dolphins

Stenella 

09:00 Atlantic spotted dolphins, Bottlenose dolphins, Short-finned pilot whales

12:00 Blainville’s beaked whales, Loggerhead turtle