08.01.2022 – The victims of overfishing

Today was my first day back on the ocean since the start of the new year and I was incredibly lucky to share sightings of Short-beaked common dolphins (Delphinus delphis) and two groups of Bottlenose dolphins (Tursiops truncatus) with some lovely guests this morning. Apart from the incredible joy that comes with any cetacean encounter at sea, our sightings also presented us with an interesting contrast.

Common dolphins are a species that is encountered more frequently during the winter months and most sightings with these beautiful dolphins, especially at this time of the year, involve feeding situations. When hunting fish at the surface, common dolphins often surround the small schools of fish in small hunting parties before once individual suddenly darts through the group of fish and launches itself into the air, taking a few of its terrified prey with it. We saw a couple of these surprise attacks today and even saw some calves joining in the pursuit, indicating that the event may have well been a hunting lesson for the young animals.

Common dolphins are efficient, nimble hunters but are known to have a smaller spectrum of prey in comparison to other dolphin species, making them easy victims of overfishing. Common dolphin populations in the Mediterranean are in fact considered critically endangered due to the overexploitation of their prey. In the Atlantic, the species is one of the many by-catch victims of super trawlers, enormous fishing vessels that have replaced smaller fishing vessels and vacuum the oceans clean of marine life. These enormous vessels are responsible for the deaths of thousands of dolphins, sharks, turtles and other marine life.

Overfishing has brought different problems for other species of dolphin. The opportunistic nature of Bottlenose dolphins has prompted these smart cetaceans to take matters into their own hands and steal catch from fishermen. Interactions between this species and Black scabbard (Aphanopus carbo) fishing boats are becoming increasingly frequent here in Madeira and we were able to witness such an event with the first group of Bottlenose dolphins today.

Of course marine life, particularly top predators such as cetaceans, are the first to feel the effects of overfishing but other very obvious victims that are often overseen when discussing these issues are small-scale fishermen. In the light of current environmental problems, it’s often easy to throw all fishermen in one pot and neglect the fact that some fishermen have always respected the ocean and harvested it sustainably.

For those who are interested in learning more about the topic, the following article gives a fantastic overview on the damage done by overfishing and includes facts that, unfortunately, are often ignored: https://yourbassguy.com/news/overfishing/

By Paula Thake

Sightings of the day

Ribeira Brava

10:00 Bottlenose dolphins, Short-beaked common dolphins