The Bluntnose Sixgill

Our objective was the deep-sea shark, the bluntnose sixgill. This ancient species predates most dinosaurs, and is a dominant predator of the deep sea ecosystem. The lead scientist on the mission, FSU MARINE LAB’S DR. DEAN GRUBBS, has been the first to put a satellite tag on one of these elusive sharks, but until now had only been able to do so by bringing them up to the surface. Because bluntnose sixgills are a deep sea species, it’s hard on them physiologically to be tagged in this way. In their typical life cycle, they won’t experience daylight, and very rarely will they feel the low pressure, warmer temperatures of surface waters. Typically, the data obtained after surface tagging of a six gill is believed to be skewed, as the shark does not return to its natural behaviors for some time after the tagging. The journey to get here has been incredibly long and complex. The idea first started when Dr. Grubbs, along with researchers Edd Brooks and Brendan Talwar of CEI, were pondering the return of Alucia (OceanX’s research vessel) to the Bahamas.

The Attempts

A brazen idea (“what if we tagged a shark from the submersible?”) turned into an experiment with a shark carcass in a pond and a subsequent first real attempt in August 2018. On that trip, a gorgeous big sixgill came in to check out the sub, but she rolled her belly at the last second. Although sixgills are massive (they can grow up to eight meters long, and on average are larger than great whites), the area suitable for applying the satellite tag is much more exact—about the size of an iPad. The second attempt was February of this year. A large sixgill came in, we pulled the trigger… and the speargun did not fire.

Needless to say, when we knew there was one more opportunity for Alucia to visit Bahamas after her end-to-end survey of the Florida Keys, we decided that this one would be “third time’s the charm.” In many ways, we had set ourselves up by promising the world that this would be it. In spite of making incremental improvements on the last two missions (which is basically how science goes), who knows if the third time really would be the charm?

https://oceanx.org/projects/tagging-a-bluntnose-six-gill-shark

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