26.09.2020 – Across the oceans and the seas

We set out onto a placid Atlantic Ocean with some very excited snorkelers this morning and eventually had the pleasure of sliding into the water with a group of around 20 Short-beaked common dolphins (Delphinus delphis). We are permitted to conduct snorkelling with these dolphins and the Atlantic spotted dolphins (Stenella frontalis) because both species have shown a seasonal site fidelity to the islands waters. Moreover, the common dolphin populations are quite stable in the Atlantic, while in the Mediterranean they remain critically endangered due to prey depletion. Meeting the common dolphins in the water with this fact in mind this morning and having some guests from my Mediterranean homeland this afternoon, inevitably inspired me to double-check which of Madeira’s .

The Atlantic Ocean and the Mediterranean Sea both house a unique variety of fauna to their waters but also have a variety of species whose distribution extends across both water bodies. The common dolphins and the widely distributed Bottlenose dolphins (Tursiops truncatus) are both examples of cetaceans that can be found both in the Atlantic Ocean and the Mediterranean region. The other two cetaceans we had encounters with today, the Atlantic spotted dolphins and the Short-finned pilot whales (Globicephala macrorhynchus) are species that prefer tropical waters and therefore do not occur in the temperate waters of the Med. Their closely related taxonomic cousins, the Long-finned pilot whales (Globicephla melas) and the Striped dolphins (Stenella coeruleoalba) are sighted frequently across different areas of the Mediterranean Sea.

Being a large ocean that stretches from pole to pole over several latitudes, it’s clear that the Atlantic is home to a larger diversity of species than the Mediterranean, a land-locked sea with saltier waters. The Mediterranean, however, enjoys its own unique concoction of species from the Red Sea and the Atlantic as well as few endemic species and subspecies of its own. Both water bodies are unfortunately subject to high levels of overfishing and the small size of the Med, makes the consequences of such exploitations more visible. Appreciating both the similarities and incredible differences between the two marine habitats should only prompt us to work more for their protection.

By Paula Thake

Sightings of the day

Stenella

09:30 Short-beaked common dolphins (Snorkelling), Short-finned pilot whales

15:00 Atlantic spotted dolphins, Bottlenose dolphins, Short-beaked common dolphins, Short-finned pilot whales