Naval technology aids studies on the behavior of marine animals

UNESP researchers used subaquatic remotely operated vehicles to study the movement and spatial distribution of rays in fresh and sea water.

By Elton Alisson

Agência FAPESP – Technology used in industry for deep-water oil exploration and other naval applications will help researchers at Universidade Estadual Paulista’s (UNESP) experimental campus, located in São Vicente (São Paulo State), to better understand the behavior of marine and freshwater rays.

Scientists are currently conducting tests on animals in captivity with Subaquatic Remotely Operated Vehicles (ROVs), which will soon be used, along with radio and acoustic telemetry equipment, to study the movement and distribution of rays in rivers in western São Paulo State and on the Northern coast.

The result of a FAPESP-funded project, the study, which is using ROVs and radio telemetry specifically for this purpose, is unprecedented in Brazil.

“The technologies complement and will allow for broader information on the spatial ecology of certain species of rays. This information is still unknown because studies of this nature have not yet been conducted in São Paulo State, especially due to high cost and the need for special training,” comments UNESP researcher Domingos Garrone Neto in an interview with Agência FAPESP.

The researcher initiated a study on the behavior of rays using radio telemetry – in which radio transmitters are inserted into the animals – in 2011 on the Paraná River on the border with Mato Grosso do Sul.

Because cartilaginous fish, such as sharks, use an electrosensorial system to detect their prey, Garrone began to question the possible effects of the telemetry transmitters on the behavior of the rays.

To analyze any possible effects of the radio telemetry equipment in rays, the researcher opted to continue the study in captivity in aquaria established especially for this purpose.

“We are finishing our experiments, and soon we will know whether the radio transmitters interfere with the behavior of the rays,” says Garrone.

On the São Paulo coast, the researcher visited the Marine and Environmental Technology Center (NUTECMAR), which operates ROVs, and saw the possibility of incorporating this technology into his research on the spatial ecology of rays.

After attending classes at the company to learn to operate the equipment, which has controls similar to those of a helicopter, Garrone intends to use ROVs in his post-doctoral project under the supervision of Professor Otto Bismark Fazzano Gadig.

“We intend to use ROVs to explore both sea and freshwater areas to analyze the behavior of sharks and rays in deep waters by day and at night,” explains Garrone.

Initially, the researcher was conducting the studies with an ROV on loan from the partner company in the project. At the end of April, the researchers were slated to begin operating with their own equipment, imported from Russia and acquired with FAPESP funding.

With an estimated cost of US$ 60,000, the ROV to be acquired can reach depths of 150 meters and can operate continuously attached to an electrical cable for 4-12 hours, drawing power from a ship or boat battery.

The equipment weighs approximately 12 kilograms, is slightly larger than a household microwave and has front and rear cameras. Operated on the surface, the cameras can capture images in real time. These images are transmitted to a monitor connected to an HD computer outside the water.

The robot also has laser diodes that allow scientists to determine the scale and size of animals that it encounters in the water, in addition to movable appendages that allow the ROV to collect material on the seabed.

Other accessories include sonar that can precisely identify targets even if the equipment is operated in murky waters, in addition to propellers that allow the minisubmarine to navigate at a speed of 4 knots and LED light emitters for nighttime exploration in locations with low or no luminosity, such as cavities and deepwater environments.

However, according to Garrone, one of the major innovations of the “Brazilian” ROV will be a system of image enhancement that allows scientists to improve the visibility of images captured in murky waters, making them extremely clear, as if viewed in swimming pool water.

“The robot will be a substitute for our presence in the water for an unlimited amount of time, allowing us to explore environments more safely and precisely, particularly in the sea, where the depth and temperature of the water tends to limit studies for long periods,” he underscores.

Accidents with rays

Garrone became interested in behavior of rays during his master’s work, in which he developed a study with fishermen in the Amazon and found that accidents with freshwater rays represented a major health concern for people in the region.

However, he did not know much about the natural behavior of these aquatic animals or about their feeding, reproduction or interactions with other species. The majority of other research available on rays was based on indirect observations of the animal, which is often caught on hooks and by trawl and longline fishing.

Through subaquatic observations, Garrone documented for the first time the hunting practices, courting/mating rituals and the movement of the rays that occur in nature.

Now, the objective of his study utilizing ROVs and telemetry equipment is to increase and improve the understanding of the behavior of marine and freshwater rays and to attempt to understand issues involving these species. For example, it is not known whether the rays living off the coast of Ubatuba (Northern São Paulo) seek warmer waters during winter and return in the summer, when the water is warmer. Nor is it known whether marine currents influence the spatial distribution of these animals.

“These technologies will give us the conditions to answer these questions securely and precisely,” says Garrone.

The researchers also intend to utilize acoustic telemetry equipment, which uses sound waves instead of radio waves, to study the behavior of rays. These studies will initially be performed in the sea. In the future, they will be extended to freshwater.

The studies are part of a research network coordinated by Professor Otto Bismark Fazzano Gadig on Brazilian elasmobranchii, such as sharks and rays, in the Elasmobranchial Studies Laboratory at UNESP São Vicente.