Manta ID

World’s First Underwater Camera Trap

To understand the lives of the elusive manta rays, we designed and built an underwater camera trap

I moved to Praia Do Tofo in Mozambique in early 2013 on a recommendation from Dr. Wallace J Nichols, to help study manta rays. Marine Megafauna Foundation has been conducting groundbreaking work in the research of manta rays and whale sharks, and they needed technical assistance in designing and building a device that could automatically identify manta rays.

Collaborator : Daan van Duinkerken

We collaborated on many aspects. Daan had developed an initial prototype as part of his thesis work, and was the expert on underwater housings and reef manta rays. I brought the hardware and firmware expertise, helping design the next iteration.

Organization : Marine Megafauna Foundation

 
 

Manta-Spots.jpg

Manta Rays are mysterious creatures, difficult to track and study. However, they bear natural spot markings which are unique to individuals and can be used to catalog specimens or monitor individuals within populations, in addition to understanding geographic range, with the help of global photo identification databases.

Marine Megafauna’s work in understanding the lives, habits and migration patters directly led to the discovery of a new species of manta rays and to the listing of manta rays and whale sharks on the IUCN Red List of Threatened Species. This allowed higher levels of protection for these amazing animals. The long term goal was to have an automated pipeline that would capture these images and feed them into Manta Matcher.

Design Requirements

 

Borrowing from Terrestrial Camera Traps

Terrestrial Traps use a beam of infrared light to detect motion. Using it underwater wouldn’t work because it is absorbed within a few feet underwater.

There were no known techniques to trigger camera traps underwater, so a large part of our research and design was targeted towards a trigger solution. We kept coming back to this phase, trying out new mechanisms.

 

Specifications

  • Needs to be installed at depths of 20 - 30 meters in reefs with strong swell

  • Must capture images of the ventral side of Manta Rays. Images of other large marine invertebrates, like sharks would be valued

  • Must not require frequent servicing and retrieval

Design Process

Manta-Complete-Trap-Electronics.jpg
 
 
The final housing design

The final housing design

Key Insight

We tested the trigger algorithm and circuitry with a red laser underwater. However, the wavelength of light dictates how far light will go before getting absorbed in water. From a distance perspective red is the worst choice, and blue the best. However, at our installation depth range of 15-30m, blue light is prevalent, so distinguishing between ambient and reflected light would be difficult, but a blue-green laser worked well in Daan’s final tests.

 
 

Testing

Did it work?

Yes and no. Turns out, electronics are not a big fan of a salty air environment or being short-circuited, or flooded with sea water at 25 meters below. All of those did happen, and getting replacement parts in rural Mozambique in 2013 was quite a challenge. Daan once had to wait more than 6 months for a camera module part. Every time we had a working prototype, something would go wrong, and we’d have to build another, usually from scratch. That being said, it did work for a short period. Daan continued to work on this project after I left, but unfortunately he eventually abandoned it.

 
 

It was quite the adventure, and the time I spent there above and below the waves, led to something incredible that I could not have imagined otherwise : Underwater VR


#conservation #conservationtech #underwater #marinebiology #design #hardware #diving #mantaray

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