Catch of the Day

Life Aboard Ship #19 July 14, 2004 #18 July 11, 2004 #17 July 6, 2004 #16 July 5, 2004 #15 June 30, 2004 #14 June 27, 2004 #13 June 23, 2004 Bouvet Island #12 June 20, 2004 #10 June 16-17, 2004 South Sandwich Islands #9 June 13, 2004 #8 June 9-10, 2004 #7 June 4-6, 2004 #4 May 26, 2004 #3 May 23, 2004 #2 May 19, 2004 #1 May 16, 2004 Punta Arenas, Chile May 14, 2004 Landfall: Visiting Islands in the Atlantic Ocean June 16, 2004 South Sandwich Islands May 30, 2004 Falkland Islands May 26, 2004 Science on the NATHANIEL B. PALMER June 24-26, 2004 June 15, 2004 May 30, 2004 Questions & Answers

Thursday, June 3: Well, we made our first more or less successful deep tow today. We went to 2700 m (8775 ft.) and got everything back. Although we tore the net completely off the head rope, we did get two nice fish specimens, one of which is important. We got one grenadier (Coryphaenoides armatus) that is a worldwide species at these depths, and is well known from the Southern Ocean. The other is an ophidiid (cusk eels, but they are actually not eels) apparently in the genus Holcomycteronus (see photo). Only one species of the family is known from the Southern Ocean, H. brucei, described in 1906. Only the holotype (a single, original specimen that establishes a species) is known, so this could be either the second known specimen, or something never recorded before from the southern ocean. Either way, it's an important capture.

You won't find these guys in the fish section of your grocery store! Coryphaenoides armatus (upper) and Holcomycteronus sp. (lower) are deep sea species found off Shag Rocks in the southern Atlantic. (Photo by Dr. Joe Eastman)

Imagine life at 3000 m (9750 ft.) depth: constant temperature (about 2 degrees above freezing), almost constant darkness (no light from the surface, but there is bioluminescence produced by some animals), great pressure (one atmosphere, 15.2 psi, for every 10 meters depth at 3000 m, 300 atmospheres equals 4560 psi), and relatively little food (no plants at all), the food sources (except where there are hydrothermal vents) are the slow drift of organic remains from above and other animals). We think of it as a really harsh environment, but it also can be viewed as the opposite: an almost friendly environment where there is much less change than we ourselves have to accommodate. No seasonal weather, nothing ever changes except possible food input from above. This allowed animals to become extremely well adapted to a very narrow range of conditions, in some cases having really amazing and bizarre specializations of body form and function. Fishes evolved improved methods of food detection and capture and reduced physiological and behavioral energy requirements. But, there are many sorts of adaptations; you can see two quite different fishes in this week's photo. Some fish have large eyes, a few are blind, many have small eyes; most have weak skeletons and muscles, but some are larger predators with better musculature and skeletons; most have much better developed abilities to sense vibrations, odor, or taste from prey (what's the difference between odor and taste in water?)

While we were towing, the weather picked up quite a bit to about 30 kts of wind. Because we cannot tow into the wind (direction of tow is determined by bottom topography not the seas) the skipper didn't want to make another tow and anyway we have to repair the net. So we are on our way to Shag Rocks, where we will set our fish traps and try to trawl without losing too much gear. All these places are volcanic, which means that they have steep slopes and lots of rocky irregular bathymetry. We are due in Grytviken, South Georgia Island, next Wednesday, 9 June.

Friday, June 4, 2004: We are at (or rather, near) Shag Rocks see http://www.icefish.neu.edu/onboard/cruisetrack/). Originally we were going to set the fish traps when we arrived at around 8 PM, but it's too rough to do it. Now we're on our way to a possible trawl station where we hope to be able to set the Blake trawl. It's quite small (only about 4 feet wide, but it has a steel frame and is almost indestructible (notice the qualifier "almost"). So it will take a lot of abuse the other nets can't. In addition, it is easier to launch and retrieve in heavy weather. Two big advantages under the present circumstances.

Saturday, June 5: We have had very good luck finding trawlable ground. The weather improved, the seas came down, and this morning we made three trawl tows and got a lot of fishes (mostly one species of nototheniid) and invertebrates. Included in the catch was a small (3-4") specimen of an Artedidraco species that has never been recorded anywhere except right at South Georgia, so this is a significant range extension. Artedidraconids are the only notothenioid fish family having a chin barbel; they are rare this far north. Rich Eakin, the world expert on the taxonomy of this group, is aboard, so he's happy! Then we went off to try to set the traps again. We wanted to set them at 450 m to catch toothfish, but were unable to do it because all the 450 m depths we could find were on steep slopes where we could not set and expect to get the gear back. Our traps are collapsible and consist of steel rod frames and netting, so they are fairly light. We set them with surface floats and a radar/light beacon so we can find them again. The result is that when the weather is rough or windy, they drag, and if we set them on a slope they are likely to end up in water too deep for the length of line to the surface floats, and sink so we would never find them.

Sunday, June 6: This morning we picked up the six traps we set yesterday. As far as fish are concerned, we got skunked. We got 30-40 crabs of two species, but that's all. We will look at them to see if they might have snailfish eggs in them, but most of them are probably the wrong species. Still, we don't have a very good idea of which species the snailfish use, so we should check all the crabs.

Click here for more information on what the scientists are catching.

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