Scientists use seals as 'underw...( ch as trawl catches catches on hooks a...)

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 teams 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.

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Contact: Peter West
pwest@nsf.gov
703-292-8070
National Science Foundation
16-Jan-2002