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First days of study near Antarctic's Palmer Station confirm absence of silverfish

Our cruise's main mission is to map the distribution of the Antarctic silverfish (for you biology buffs: Pleuragramma antarcticum) along the Antarctic peninsula.

The silverfish was once abundant along the entire length of the peninsula, but now it seems to be missing from much of the northern half.

How do we know? Penguins and other seabirds used to feed it to their fledging chicks, the time when the young birds need the highest calorie meals to grow quickly. You see, silverfish are fatty, a high-energy food that is just the thing for gaining weight, developing swimming muscles, and growing dense, protective feathers.

So, we are on a "quest for silver" as we hunt the elusive silverfish along the entire length of the peninsula. Our main tools in the hunt are scientific nets that allow us to get multiple samples in one tow.

One net cluster is small, for catching very young silverfish, or larvae, as scientists know them. Each of nine nets is 1 square meter (about a yard) with fine mesh.

Our larger cluster has six nets, each of which is 10 square meters. It looks a bit like a beached whale, but it catches adult silverfish very well.

We also have a small rectangular net known as a Tucker trawl that we use for quick collections of fish and krill for experiments, and a bottom or "otter" trawl (bottom trawl on the way up).

Taken together, we can catch everything from good-sized fish to very small plankton, and we can catch them from surface to bottom. If there are silverfish around – we will catch them.

(The various nets are displayed in the photo gallery at right.)

It took a while to get all our sampling gear put together. We did as much as we could while we were in the calm waters right near Palmer Station.

We completed the tasks on the way to our first sampling site, which was a 6-hour steam out into the open waters west of Palmer Station (see map in photo gallery).

There we sampled with all of our nets from surface to bottom. After trying all of our nets multiple times our conclusion so far is: The penguins were right. There don't seem to be any silverfish near Palmer Station.

We will sample again later in the cruise to make sure. Notice from the pictures that some penguins were even giving us a helping hand while we were trawling.

We are headed for Charcot Island – a two-day trip south on the peninsula into nearly uncharted waters.

• • •

Finally, the answer to a question from a Florida-based editor: How cold is it?

We have been lucky so far. Temperatures have been hovering between minus-2 and 0 degrees Celsius, or 28-32 degrees Fahrenheit. The wind chill feels like 8-10 Fahrenheit. So, yes, it's cold, but not as cold as Minnesota. Winds have been bouncing between 10 and 25 knots and seas have been about 4 to 6 feet. We have been getting a lot of snow, including a hail-like snow that is called grauple.

First days of study near Antarctic's Palmer Station confirm absence of silverfish 03/25/10 [Last modified: Thursday, March 25, 2010 2:20pm]

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