A yellow high-pressure underwater housing for a camera with two side pods showing red LED lights is mounted in a black cubic frame for deposition onto the sea floor

Camera Trap for Sharks

Markus Horning

Markus

November 16, 2023
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Creatures of the Deep!

 

Several thick arms lined with two rows of sucker cups each originate from around the mouth of an octopus, as seen from the underside of the octopus that is back-lit by red light illuminating the deep sea scape
The Kraken

 

This summer we have started using the Deep Submersible Camera Trap or DSCT here in Resurrection Bay, in the Kenai Fjords region of Alaska. The DSCT is a video camera in a high-pressure housing capable of withstanding the enormous pressures encountered in the deep ocean at hundreds of meters of depth. It is capable of being lowered to a depth of 750m (2,500 ft), and has a video recording endurance of up to 48 hours of continuous HD video.

 

A yellow high-pressure underwater housing for a camera with two side pods showing red LED lights is mounted in a black cubic frame for deposition onto the sea floor
The Deep Submersible Camera Trap, here pictured sitting on a dock. The cubic, tubular  frame can be configured in different ways to change camera orientation, and to add or remove ancillary equipment. We launch the DSCT from our small research vessel, the Tiburon.
A video camera in a deep-sea high-pressure housing mounted in a black tubular, cubic bottom lander frame is sitting on the deck of a small boat. The frame also has two black cylinders that are acoustic tracking receivers.
The Deep Submersible Camera Trap sitting on the deck of a boat. In addition to the video camera and lights in a yellow high pressure housing, the black tubular lander frame also holds two Innovasea acoustic tracking receivers.
A video camera system in a yellow high pressure housing held in a black tubular bottom lander frame is balanced on the gunwale of the research boat ready to be lowered into the ocean. Two salmon heads are attached to a pole extension of the lander frame, and are used as bait for the camera trap
The DSCT ready to be lowered into the ocean with salmon heads as bait. The bait is secured on a string tied to a rod dangling the bait in front of the camera port.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In addition to the video camera and massive amounts of lithium batteries in the central part of this yellow-coated aluminum housing, the two side pods hold LED lights capable of illuminating scenes that we can never dream of observing ourselves directly. We use deep red LEDs that emit a red light at a wavelength of 660nm because it is unlikely that most deep sea organisms can actually see this color of light. Why? Because red light is much more heavily absorbed by seawater than shorter wavelengths, such as green or blue. In the deep ocean, there is no natural red light, and hence no need for deep sea creatures to have evolved the ability to sense red light. Our camera however can record red light, and we are less likely to turn off creatures with our bright LEDs than if we used green or white light. So, we can see them, but they can’t see us (or our yellow subcam). The downside is that red light does not reach far at the bottom of the ocean.

 

The whole housing is fixed in a cubic lander designed to securely hold the camera and associated systems on the sea floor. The lander can be configured in a number of ways, with different orientation and selection of ancillary features. This lander also houses some additional devices: there is an electronic data logger that records pressure, light levels, water temperature, as well as conductivity and soon also dissolved oxygen levels. In addition, there are two acoustic tracking receivers made by Innovasea/Vemco. These receivers can detect when acoustic tracking transmitters emitting 69kHz ultrasonic chirps are nearby, such as the acoustic transmitters that we use on Pacific sleeper sharks. This feature is actually quite exciting, as we can potentially use this approach to begin to estimate the local abundance of these sharks in our waters from the proportion of sharks detected on video that carry the acoustic transmitters. This would be a new application of the classic ‘mark-recapture’ population assessment technique.

 

The deep sea is often a sparse environment with little food or prey. As a result, the likelihood of actually ‘trapping’ many creatures on video might be fairly low, unless we take steps to attract them. That is why we use bait on the DSCT. A baited camera trap is much more likely to net us some interesting video captures, but it will also result in a specific bias, or in non-random sampling of the demersal fish and benthic epifauna. We use fresh salmon heads as bait for actually catching sharks for tagging purposes, but also on the DSCT as bait to attract other demersal organisms. We drop the camera over the side of the boat and lower it to the sea floor, with a line connecting the DSCT to a surface buoy for later retrieval. In the summer of 2023, we managed to complete seven deployments of around 24 hours typically, in Price William Sound and mostly in Resurrection Bay.

 

So what have we seen?

 

The head of a shark with eye and mouth. The color is a dark red from the red LED illumination.
A Pacific sleeper shark as captured by the Deep Submersible Camera Trap in Resurrection Bay, at a depth of about 200m.

 

So far, we have seen many different deep sea creatures, from the octopus at the beginning of this post, to many crustaceans and also different species of fish such as halibut, Pacific cod and spiny dogfish, and …. drumroll …. the sleeper sharks we are studying!

Stay tuned for more on our use of the Deep Submersible Camera Trap, we will post some actual video clips from the DSCT soon!