Dog recovers lost Argos tag from a Leafscale Gulper Shark
At the end of March 2022, Cristina Rodríguez-Cabello researcher of the Spanish Institute of Oceanography (IEO) in Santander (Spain), was working at her Centre when she received an unexpected yet exciting call from France.
One of the archival tags she had attached to a deep-water shark the year before had been discovered on a beach in the North of France by a couple and their dog.
So, how did a tag that had been attached in the Marine Protected Area of EL Cachucho (Le Danois Bank, Cantabrian Sea) end up in Audierne (France) near Brest?
The tag, programmed to detach after 140 days (early March), had been attached to a mature, male leafscale gulper shark, Centrophorus squamosus, measuring 109 cm on the 18th of October 2021. However, March came around and there was no sign of the tag. Before we investigate further, here’s some information on the main character of the story (the shark, not the dog).
The leafscale gulper shark is a deep-water shark and can be largely found in the East Atlantic between Iceland and South Africa, including Madeira, the Azores, and the Canary Islands. Unfortunately, the leafscale gulper shark has been exploited commercially for many years and has been in a strong but steady decline since the 1990’s leading to its status being established as Endangered by the IUCN.
Back to the investigation
Once Cristina and her team recovered the tag, they were able to download the data. They found that the tag had released prematurely on the 21st of December, 2021which meant that the tag had recorded data for two months instead of the 4 months initially programmed. But why did it release prematurely?
According to the depth profile on the 21st of December, the shark dove down to 1818 m, activating the depth threshold, which prevents the tag from being crushed. Once the depth threshold has been reached, the tag detaches itself to ensure that the data is safeguarded.
The tag arrived on the surface on the same day south of Ireland waters and drifted until it reached France’s northern coast where the secondary character of our story (the dog and its owners) found it on the beach.
While previous studies have shown that the leafscale gulper can make long migrations, many questions remain unanswered: Was the shark following a specific track? Was it swimming near the slope? Why did it go up and down particularly in the last period? Was it following prey, or did it come across an obstacle?
Only a small part of the shark’s biology and behavior is known, and research is still going on. However, more funding will be needed, and Cristina hopes that she and her team can find some of the answers to these questions which will improve our knowledge on this great shark.
Cristina and IEO thank once again Jump and Jump’s owners Mr. & Mrs. Le Duc who, whilst taking their daily walk along the beach, found the tag and sent it to them.