NSF PR 02-04 - January 16, 2002
Scientists Use Seals as "Underwater Eyes"
Technology provides rare
glimpse of rare fish species
By employing one underwater species to "spy" on two
others through novel use of technology, Antarctic
researchers have gained new insights into two little-known
fish species. The team expanded their knowledge base
by equipping Weddell seals to follow the fish and
record their behavior.
The fieldwork by an eight-member team at McMurdo Station
in Antarctica provides a rare glimpse into the habits
of two very important Southern Ocean species, the
Antarctic silverfish and the Antarctic toothfish,
which is prized by commercial fishing fleets. It could
also have wider applications in studying other species
that thrive at great depths, the researchers argue.
The results of the work, supported by the National
Science Foundation (NSF) were reported in the online
version of the journal Marine Biology. The
paper will appear in print in the March edition of
To obtain the images and data, Lee Fuiman of the University
of Texas at Austin, Randall Davis of Texas A&M University,
Galveston, and Terrie Williams of the University of
California, Santa Cruz, equipped 15 Weddell seals
over the course of three Antarctic summers with a
video camera, infrared LED's and data recorders to
track both their movements from their breathing holes
through the water and their interactions with their
"This use of a marine predator as a guided, high-speed
sampling device for its midwater prey provided clarification
and new insights into the behavior, interactions,
and ecology of species that have been especially difficult
to study," they write. "This new information expands
the base of knowledge of two of the most important
fish species in Antarctica and indicates that some
existing notions about their distribution and behavior
may need to be revised."
Much that is known about these key fish species comes
from a variety of indirect evidence such as trawl
catches, catches on hooks and from the stomach content
of predators. But the camera and data recorders allowed
these scientists to "accompany" the seal as surrogates
on their hunts and to record firsthand what the seals
and their prey were seeing and doing.
For the silverfish, this meant that the majority of
the 336 fish were observed at depths greater than
160 meters (524 feet), with a few being watched at
a depth of 414 meters (1358 feet). In the case of
the toothfish, most encounters began at approximately
180 meters (590 feet).
The team's findings shed new light on the behaviors
of the two species. For example, the researchers now
believe, based on the "seal cam" data, that the silverfish
migrate from deeper to shallower water using ambient
light, even in the absence of a sunset during the
Antarctic summer, as a cue.
"Nevertheless," they write, "our few observations of
[silverfish] under the thicker permanent ice shelf
suggest that light intensity may not be the only determinant
of vertical position." More observation, they say,
is needed to see if other factors, such as the distribution
of predators or prey, which also may respond to the
amount of ambient light, may also play a role in species
distribution. The data also indicate that toothfish
may be more common at depths less than 200 meters
(656 feet) than previously thought.
Although their data were gathered in Antarctic waters
and the researchers acknowledge that all data sampling
techniques have their limitations, the "seal cam"
technique, they argue, is promising and "could be
used to study other pelagic and deepwater fishes and
invertebrates that are otherwise impossible to observe
in their natural environment."
Editors: For b-roll of Weddell seals equipped
with cameras, contact Dena Headlee, (703) email@example.com