By Mary Lenz

Enlisting the help of 15 Weddell seals as under-water photographers, researchers from The University of Texas at Austin have discovered important new information about two ecologically important fish species living far beneath the ice pack in the dark and frigid waters of Antarctica’s McMurdo Sound.

Researchers used video sequences with synchronized positional data recorded by Weddell seals to describe behavior of two important fish species.

Dr. Lee Fuiman, a behavioral ecologist with the university, said this is the first research project to employ marine mammals to photograph an entirely different animal species by carrying a combination video camera and data logger.

Fuiman

Co-authors include Dr. R.W. Davis of Texas A&M University Galveston and Dr. T.M. Williams of the University of California Santa Cruz.

Fuiman, Davis and Williams previously have used seals, whales and dolphins as camera operators for research on their own species.

"Few details are known of the habits of Antarctic midwater fish, especially those living below the heavy pack ice and shore-fast ice, because they are difficult to capture or observe at depth," Fuiman said. "We used video sequences with synchronized positional data recorded by Weddell seals to describe such things as the location, movements, population trends and swimming behavior of the two fish species -- popularly known as Antarctic silverfish and Antarctic toothfish."

Seals 'observed' three different species of fish: a) Antarctic silverfish, b) Antarctic toothfish, and c) bald rock cod. Weddell seals frequently eat silverfish and rock cod and sometimes the much larger toothfish. Bald rock cod live just under the ice surface. Silverfish and toothfish inhabit much deeper and darker waters.

Previous knowledge of the habits of these two fish has been gained by trawling in ice-free areas, an inexact method at best, Fuiman said.

The researchers used black-and-white video and miniature, low-light sensitive video cameras encircled by an array of near-infrared light-emitting diodes (LEDs).

Scientists believe that the infrared illumination from the LEDs was invisible to seals and fish and, thus, did not interfere with normal behavior. Yet, it enabled the camera to record images underwater in complete darkness to a distance of about one meter.

Ten male and five female seals made up the film crew. The sea mammal film crew members worked for four to five days at a time over three springtime field seasons at McMurdo Station. The research was supported by the National Science Foundation.