Research Expeditions over the Ikaria Trench

by Ambrosine Clark / Friday, 20 August 2021 / Published in Intern Experience, Marine Mammal Team, Work Journal

During the research expeditions over the Ikaria Trench, the Archipelagos’ marine mammal team aim to gather data on the species living over this important hotspot, to increase our knowledge on their behaviour, distribution and density. Weather-allowing, boat surveys extend to further areas during multiple-day research expeditions.

During the multiple day surveys up to the Ikaria trench, our research team aims to collect data on all species that can be found in this hotspot, such as the striped dolphins (Stenella coeruleoalba) seen above.

The surveys usually occur between the islands of Ikaria, Fourni and Samos. This area is characterized by a deep-water trench that exceeds 1000 meters in depth and hosts a rare diversity of marine life. The Ikaria trench is one of the most important migratory routes and feeding areas for large marine mammals in the North-East Mediterranean, such as sperm whales (Physeter macrocephalus), Cuvier’s beaked whales (Ziphius cavirostris) and Risso’s dolphins (Grampus griseus).

Cuvier’s beaked whale (Ziphius cavirostris) are one of the most elusive marine mammal found in the area. The data is deficient for this species, which can be partially explained by beaked whales’ ability to dive to incredible depths (one individual was recorded to dive 3 hours and 42 minutes, to a depth of almost 3 kilometres)

Cuvier’s beaked whales and sperm whales are deep-diving species that can descend to more than 1000 meters and stay underwater for over an hour. Little information is available on their distribution in the Mediterranean, due to their short surface period and long dive time, making it difficult to observe them at open sea. Archipelagos’ Marine Mammal research team surveys the trench as many times as possible in the year in order to gather information on these understudied species. In the past six weeks, we have already been able to collect data on Cuvier’s beaked whales on three separate occasions. Photographic and behavioural data has also been collected on the Risso’s dolphin (Grampus griseus). This migratory species, found within small groups, feed on cephalopods such as squid. Risso’s dolphins are easy to identify due to their white scars, which increase with age.

Risso’s dolphins (Grampus griseus) are other inhabitants of the Ikaria trench that have been observed by the Archipelagos research team. Their white scaring makes them easily identifiable for photo identification.

During the boat surveys, the marine mammal team records several types of data. Interns continuously collect data regarding environmental conditions, marine litter count, bioacoustics, microplastics and seabirds. When a sighting occurs, the team records photographic data with DSLR cameras, acoustic data with a hydrophone and behavioural data through datasheet notations and with a video-camera.

Microplastics data being recorded by the marine mammal research team on one of our research vessels.

These boat surveys are an important step in Archipelagos’ mission to fill the knowledge gaps concerning marine mammals in the Aegean Sea. The data we collect is being analysed to discover more about whales and dolphins’ behaviour, population sizes, migratory routes, anthropogenic threats, and many other factors. Our research has helped advise conservation methods for Mediterranean marine life for over 21 years, and continues to do so with our ever-expanding databases.