New ultrasound scanners helping to conserve Manta Rays

February 25, 2020

Swimming with manta rays is almost a
therapeutic experience I would say. Being in the water with these animals makes
you forget about anything else. The interaction with this animal just clears
up your mind and opens up your heart and your soul and you just want to be down
there as long as you can and sometimes you have the feeling that mantas feel the
same way about us. So they want us to remain with them for as much as possible. Manta rays are undoubtedly among the most charismatic creatures of our ocean, they
are on top of the list of animals that any ocean lover wants to see and swim
with, but like many species in the wild on our planet they face a number of
serious threats. They are increasingly fished and their populations are at risk. So this project aims to establish the factors that are responsible for the
annual fluctuations in breeding, why animals breed in certain areas and not
others to help inform the conservation of these species both in
the Maldives and other areas of the world. In particular we we’re using a
newly developed underwater ultrasound machine. So this machine is able to scan
and visualize the internal structures of manta rays without any contact with the
animal it uses saltwater as the contact medium. It’s a light and portable machine
which will allow scuba divers to approach the animal and obtain images of
particularly the reproductive tract without causing any disturbance or
stress to the animals themselves. Ultrasound examination of wild manta rays
have only been attempted a very few times and that was done with big, bulky
ultrasound machines – very difficult to maneuver underwater the ultrasound
examination were made by making contact with the animal and the innovative
aspect of this project is that it uses a completely new ultrasound machine which is
very small light and portable and is mounted on a 3d printed rig with handles
which makes it very easy to maneuver underwater. To actually scan a manta ray, we
dive close to a cleaning station down to about 20-30 meters in sometimes
difficult conditions – ocean currents, low visibility. We approach the animal from
above so that the animal doesn’t feel the presence of the diver, extending our
arm in order to get the probe as close as possible. While above the animal we
are adjusting our movement to minimize the impact and distress to the manta. We then position the ultrasound scan about four or five centimeter from the animal
targeting the left side of dorsal fin which is where the reproductive
structures such as the ovaries and the uterus are visible. The sonogram or images are recorded on a mobile phone and then analyzed in the lab. Our research
project is taking place in the Republic of Maldives. The Maldives has a largest
population of reef manta rays in the world, sightings of these animals are very reliable consistent and thus allow us to
obtain ultrasound examination of the same individual multiple times
throughout the entire gestational period. So we were able to determine the stages
of maturity and when animals are becoming reproductively active, the
stages of pregnancy, the development of the fetus and importantly whether
animals maintain that pregnancy and actually give birth to a live animal. Understanding some of the fundamental details about their reproductive
strategies enables the populations to survive and hopefully flourish and our
hope is th at this research project will contribute to that knowledge in order to preserve the species for future generations.

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