Under pressure: Submersible Search for Six Gill Sharks
September 24th 2019 was no ordinary Tuesday for three members of the Expedition Development Team. Karen K., Craig M. and Trent Tresch were on their way to explore the depths of the Puget Sound. Off the coast of Everett Washington they boarded Cyclops 1, a steel hulled submersible capable of holding up to 5 passengers to a maximum operating depth of 1640 feet below the surface.
On this particular day the LEX divers would be in search of the elusive Hexanchus griseus, also known as the Six Gill Shark, while diving to about 440 feet. Deep within the waters of the Puget Sound lurk several shark species, the Six Gill’s are particularly notable because their features are more similar to their prehistoric ancestors than their modern-day dogfish and Greenland shark relatives. OceanGate, the company who owns and operates the submarine, along with participating researchers from NOAA and the University of Washington, have been conducting a series of these types of research dives in an effort to establish a baseline understanding of the area’s local shark population demographics.
This large, deep water shark is an example of a significantly more primitive species found only as fossils. It has a broad, flat head, large green eyes, and a small, single dorsal fin far along its back. Average length is 15 to 16 feet long, and it is gray to olive to brown in color. It feeds nocturnally and ambushes its prey, but because it lives at depths, little is known about it.
At around 8:45am the submarine was transported out to the dive location in Possession Sound. The entire 12,000 pound unit sits on top of a towable floating dock called the Mobile Subsea Launch and Recovery System (MSLARS). At 10am the team loaded up a retired coast guard response boat and traveled separately to rendezvous with the others stationed at the deep dive site.
After a brief photo op, the three explorers proceeded to ingress the small exploratory vessel.
The large three-inch-thick acrylic dome was an ample source of light into the hull itself. All that was left was for the team to get familiar with their stations and hold tight for the pilot to complete pre dive checks. 3,2,1, DIVE!
As the entire floating dock leaned back and began to submerge, the seemingly clear water and accompanying bubbles began to devour the sub. Once fully under the surface we hovered, then left the safety of MSLARS.
Along a dive line, to guide the decent, they began their journey to the bottom of the Sound. Water colors shifted from the initial clear to a bright green. As they motored down, deeper and deeper, green turns to black.
These green displays are a popular highlight for many undersea explorers that visit the Pacific Northwest. For many recreational scuba divers this is a much different experience compared to the tropical blue water locations visited. However recreational scuba divers limit themselves to around 100 feet deep, the submarine was descending to over 4 times that depth.
Trent and Karen sitting at the front of the sub’s acrylic dome. The light green emerald color glowing through.
Sinking to the bottom took only a matter of 10 to 15 minutes and here is where they began their wait, hoping to capture a Six Gill on camera. For the next three hours the team would spot and record different species that they located in the area. One of the first visitors were the Aeroworms, a small clear animal that flocked to the lights. Others that followed included: Shrimp, Rock crab, Rat fish and Ctenophores. Sadly no Six Gills.
With no success spotting the sharks around the bait they took off to explore the shelf they were positioned just north of. With only a few feet of visibility they were reliant upon the sonar system to guide them through the thick particulate. After only a few moments, the decision to transit along the ocean floor paid off. The worlds largest jelly fish sprawled itself dead center of the acrylic dome!
With tentacles up to 120 feet long, some individual Lions mane even rival in size the blue whale, the largest animal in the world. Most of these jellyfish live in the Arctic and North Pacific Ocean from Alaska to Washington where the waters are cool. Its ‘mane’ of long, hair-like tentacles hanging from the underside of its bell-shaped body is the inspiration behind the lion mane’s common name. The mouth is situated on the bell’s underside, surrounded by tentacles that are divided into eight clusters of up to 150 tentacles each. These tentacles are equipped with nematocysts containing poison that stun prey when they are enveloped. The top of the bell is usually dark yellow or red in color and thick in the center, but thins out towards the edges. The lion’s mane jellyfish also possess bioluminescent abilities, meaning it’s able to produce its own light and glow in the dark underwater.
While the teams excitement grew over the large sighting, another point of interest revealed itself in the distance. A large rock the size of a car. This was a perfect opportunity to test out Cyclops’ laser measuring unit and take some 3D scans.
The opportunity for true exploration is one that can still be found in the depths of our ocean’s today. As of the year 2018, the National Oceanic and Atmospheric Administration (NOAA) estimated that as much as 80 percent of the world’s oceans are unmapped, unobserved and unexplored. Reaching these regions deep below the ocean’s surface is difficult, time-consuming and expensive.
To learn more about OceanGate and their work, please visit their website: https://www.oceangate.com/
“The sea, once it casts its spell, holds one in its net of wonder forever.” -Jacques Cousteau
Published 2020 https://underseadive.wordpress.com/