A team of marine biologists has made history by being the first to tag an animal from a sub.
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The animal in question was a bluntnose sixgill shark (Hexanchus griseus), aka Atlantic mud shark, cow shark, or bulldog shark (the creature has many more names besides). It is an elusive species, existing thousands of meters below sea level over the continental and insular shelves and moving to shallower waters at nighttime to feed.
But now, OceanX has released videos of individual sixgills going about their business – and the images are remarkable.
See this one with an appropriately eerie soundtrack:
This one complete with running commentary:
And this one from Facebook:
Because of its deep-sea predisposition, we know relatively little about this isolated giant. An average shark will reach lengths of a little more than 4.5 meters – 15 to 16 feet, or a similar size to a great white. Some can reach lengths of 8 meters or 26 feet. But we do know it is a dominant predator of its deep-sea environment. We also know that it is an extremely primitive species, predating most dinosaurs.
The shark gets its name (and there is no shocker here) from its six gills, an evolutionary throwback to some of the earliest shark species from the Early Jurassic period. Most sharks alive today have five. Indeed, compare modern sixgills to the fossil record and it looks like they have changed little over the last 200 million years.
Researchers hope to improve their understanding of these mysterious creatures by tagging individual sharks and tracking their movement. While scientists have successfully lured sixgills to the surface for tracking purposes in the past, the process can leave the animals disorientated and confused – a scenario that is neither nice for the shark nor conducive to collecting reliable data. The scientists at OceanX say the information is often skewed as it takes some time for the shark to return to normal behavior.
And so, the team attempted a novel approach: tag the sharks in their preferred environment, 2,500 meters (8,200 feet) or so below sea level.
The first attempt took place in August 2018, when "a gorgeous big sixgill" approached the sub. Unfortunately, she rolled her belly at the last second, hindering the team's efforts to apply a satellite tag on the part of her body suitable for doing so, an area roughly the size of an iPad. The second attempt was equally unsuccessful. In February 2019, the team attempted to tag a sixgill but the speargun did not fire.
It was third time lucky and the team was able to achieve their goal on the next attempt in June 2019. After a series of setbacks (day one: the speargun failed. Day two: the relevant adjustments to the speargun were made, but the sixgills were a no show. Day 3: a large grouper gatecrashed the party, successfully tagging itself in the correct position), the researchers got what they came for and tagged a large male.
Not only does this mean we should uncover more on the mysterious lives of sixgills, but the success of the mission demonstrates the possibility of tagging deep-sea creatures with the use of a submarine – opening up the possibility of learning more about life on the ocean floor. Believe it or not, we have better maps of the surface of Mars than we do of the ocean. According to NOAA, more than 80 percent of the ocean remains "unmapped, unobserved, and unexplored".
[H/T: OceanX, Science Alert]
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