Humans have been navigating Western Mediterranean waters alongside whales for thousands of years. Species like fin whales and sperm whales are amongst the largest animals on the planet, yet we know very little about the seasonal movements and patterns of these enormous mammals. For the past few years the Oceanografic Foundation in Valencia, working together with Polytechnic University of Valencia and the University of Alcala have been gathering data surrounding whale vocalization to deepen our understanding of these giants of the sea in order to help protect them. I was fortunate to be able to join the research team on their most recent expedition to recover a hydrophone which had been sitting on the sea floor gathering whale vocalization recordings for the past seven months.
A bit of background on fin and sperm whales
Fin whales are massive mammals found in oceans across the world. A mature fin whale is longer than two full-sized busses (over 27 metres) and weighs more than four full grown elephants (over 70 tons). One of the questions the research team is trying to answer is whether fin whales stay in the Mediterranean or leave the area via the Strait of Gibraltar to meet with Atlantic populations.
Measuring up to 20 metres, sperm whales are the other giants of the Mediterranean. They have an enormous head that makes up one-third of their length. That huge head is famous for its historic portrayal of a “battering ram” used to sink the ships of early mariners (mostly a fisherman’s tale). In reality their heads are filled with liquid wax called spermaceti used generate powerful and focused clicking sounds for echolocation and communication.
Retrieving the hydrophone
The research team and I boated two kilometres offshore from Cabrera Archipelago Maritime-Terrestrial National Park to recover the cetacean monitoring hydrophone (SAMARUC system). The process to recover the hydrophone is simple enough. First, we send a signal from a transmitter called a Deck Box to a holding device located on the seabed, 96 metres below the water’s surface. This triggers the holding device to release the SAMARUC system which contains the hydrophone and data logger attached to buoys — the unit floats up to the surface and we pick it up.
Simple enough, that is, if all the equipment is functioning properly. We soon discovered that our signal was not reaching the intended target and that a key component of the Deck Box circuit board had been damaged. Months of preparation had gone into this trip and it was potentially all being compromised by a faulty connection. After a stressful afternoon of problem solving, our resourceful team managed to repair the Deck Box and find a boat and Captain to take us back to the research site the next day.
The following morning we set out to sea again, this time to successfully recover the SAMARUC system. When we pulled the unit up onto the boat the entire team cheered and celebrated like a sports team winning a championship — finally holding in their hands the fruits of their labour. After the burst of enthusiasm, the team immediately shifted its focus to the next task at hand — extracting the data to see which whales had passed by the site.
The data is in the form of 45 days of sound files which will be catalogued and analyzed to see which whales were in the area and what they were doing. The information extracted from the device retrieved will be added to a larger dataset allowing the team to accurately map out fin and sperm whale migration routes and learn more about their interactions and social dynamics.
For the Oceanografic Foundation, this data will also support the development of scientific publications and help the 1.3 million annual visitors to the aquarium site in Valencia to develop a deeper understanding and a personal connection to the Mediterranean. This is an important outcome, as many people living in the region have a limited understanding of the amazing body of water at their doorstep. Filling the gaps in our knowledge of these whales is a critical component in developing an appropriate species conservation plan in order to protect some of the biggest animals on the planet.
Dolf DeJong is general manager of Vancouver Aquarium and the former vice president of conservation and education at the Vancouver Aquarium Marine Science Centre. He was recently on assignment at the Oceanografic Aquarium in Valencia, Spain, supporting the staff of Europe’s largest aquarium as they expand their conservation and education efforts. His On Assignment blog series chronicles some of his adventures and experiences while he was on dispatch in Spain.