Don’t Sleep on these Sharks

All photos/handing conducted under ADF&G permit # CF25-022

Written by: Lizi Byrd, MSc Student

Picture Prince William Sound on a sunny day—still, blue-green water reflecting gossamer clouds, frigid glaciers, and snowcapped mountains in the peak of summer. We sit in the middle of the sound drifting. A Marbled Murrelet flies overhead. We’ve got eyes on a pair of otters, mom and pup, resting in the calmer waters of the fjord. Within fifteen minutes of each other, we’re passed by a group of kayakers and a pod of humpback whales. Although breathtaking, the picturesque scenery at the surface is far from what draws us here. It lays in stark contrast to our objective, waiting in the freezing, pitch black waters of the deep. Our purpose lingers near to a thousand feet below, razor-teeth wrapped around our bait and gnarly hook. We have come to Prince William Sound for Pacific sleeper sharks.

Pacific sleeper shark captured at depth on Wildlife Technology Frontiers’ Deep Sea Camera Trap.

Pacific sleeper sharks (Somniosus pacificus, PSS) are one of three main shark species that regularly inhabit Alaskan waters, alongside salmon sharks and spiny dogfish. They are the largest, most mysterious, and (in my opinion) most captivating of the three. They are a long-lived and slow-moving shark in the Squaliform order, closely related to the better recognized Greenland shark. PSS are found worldwide from shallow, polar waters to abyssal depths in temperature and tropical regions. Despite their wide range and frequency being bycaught in commercial fisheries, very little is known about their role in Alaskan Ecosystems. Their fine-scale habitat selection, spatial distribution, and how these overlap with prey species is the focus of my Master’s research. The Bishop lab and key collaborators like Dr. Markus Horning have been researching PSS for years. This summer I was afforded the opportunity to tag along and help with tagging efforts.

Into the Field

Before the sharking could begin, I first had to become certified as an operator on both of the research vessels we’d be using for the trip: 21ft Tiburon and 14ft Enhydra. To accomplish this, I spent a portion of my June in Seward, going out daily and deploying the Deep Sea Camera Trap whenever the weather would allow. By August, I’d met the certification requirements. It was time to head out. 

Home sweet home at Squirrel Cove with the spoils of a weathered-out day spent berry picking. 

We were based at the public use dry cabin in Squirrel Cove, about a twenty minute boat ride from the town of Whittier. Every morning saw us headed out, weather and sea state permitting. To catch the sharks, we used modified longlines with two to three salmon-baited gangions—a process which required at least three people to set up. Each day we’d set four of these lines at a range of depths from 700 - 1,200 feet. In line with tradition—and a vital part of the process—a gummy bear was ritually sacrificed to the deep after each deployment. Then, we waited. Lines soaked for a minimum of four hours before we could return to find whether we’d caught anything, so there was always an abundance of time to kill. Some days that meant sandwiches and reading on the boat or heading back to the cabin for the same. Some days it meant berry picking or tidepooling around Squirrel Cove! Regardless of how the wait was spent, the next step was always the same: head back to the buoys marking the drop site, start pulling up the line, and hope for a shark. 

The team on Tiburon at the start of a pull, taken from Enhydra.

Shark on!

From the 4x (sometimes 8x) daily drops this summer, we caught four sharks. First, we moved the ~3m (~10ft) shark from the tiny Tiburon with the line hauler to the even tinier Enhyrda, where the shark could be laid in a floating stretcher alongside the boat.

Measuring the total length (TL) of the sharks takes two people; this individual was just under 3m long. Photo by John Skinner.

Once the sex of the shark is identified (visible claspers indicate male), they’re laid out dorsal side up on the stretcher alongside Enhydra. Data collection and tagging begins. Eye parasites, if present, are noted and photographed, the total length of the animal is recorded, and a clipping from the tip of the forward dorsal fin is collected. Tagging implementation follows. 

Past sharking efforts have produced data on the temperatures and depths that these sharks inhabit. What we still don’t know is how and where they move through the water, and what behaviors they're using to find prey. To start to answer these questions this summer, we used three different types of tags. The most exciting was the SomniVision platform tag. SomniVision includes an attached eDNA collection device (PESCA, designed by co-PI Dr. Jessica Glass) and a modified GoPro to record video footage. It was programmed to detach from the shark after 24 hours, at which point we tracked down its GPS location and retrieved it from the water. We also deployed the Shark Ocean Observing System, or SOOS, another 24 hour platform tag that served as a shark-mounted CTD recorder for that time. CTDs capture conductivity, temperature, and depth data, essential information for understanding the physical properties of seawater.

Lizi attempts to keep the shark in place while Dr. Horning attaches the SomniVision platform tag. Photo by John Skinner.

Both platform tags record information about the sharks’ environment at a scale we’ve never before had access to. While only two of the four sharks captured this summer received a platform tag, each one at a time, all four received two Wildlife Computers mrPAT mark report pop-up transmitters. These two mrPAT tags are programmed to detach at 30 days and 8 months respectively. They allow us to track more large-scale movements of the sharks, and transmit data like that of previous years that I’m using for my thesis work. 

Despite the long days, the outhouse, and the small cabin, there’s nothing I would change about this fieldwork experience. I’m so grateful to have been given a chance to see how the data I’m using for my thesis research was generated and to be able to do so with such an awesome group of scientists. This opportunity was unforgettable, and one that allowed me to come face to face with one of my lifelong favorite animals. I can’t wait to see what questions will be answered about this highly misunderstood and understudied shark. 

A small subset of the amazing team from this summer. From left to right: Lizi Byrd, Kodi Haughn, and Dr. Markus Horning. Not pictured: Dr. Amy Bishop, Dr. Jessica Glass, Catherine Spangler, and John Skinner. Photo by John Skinner.