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Life Aboard Ship, Dispatches From South of the "Roaring Forties"
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May 23, 2004
We have been trawling now for five days, with less success than we hoped. We have caught a fair number of small icefishes, but not as many, as large, nor as many species as we wanted. I have been pretty happy, though. I have got six snailfish of (I think) two species. I study them after they have been transferred to alcohol from being fixed in formaldehyde. So far, I have identified Careproctus falklandicus, described in 1905. It is not rare here, but not very common in collections in the northern hemisphere, so our specimens will go to the Smithsonian. In addition to the snailfish, we have collected four species of icefishes (all pretty common ones), two sculpins, and hagfish. We got one 500 mm (19.5”) toothfish (otherwise sold as Chilean sea bass in markets and restaurants at home) and it was the occasion of a sort of dissection party in which the blood went to an Italian, the heart to an American, the spleen, kidney, brain and other tissues to a South African, and muscle tissue was shared among several more folks. All these tissues are for specialized genetic and physiological analyses requiring fresh (living) tissues to work with - can't just go out to the store and buy a filet.
This is not
a well-known area of the Burdwood Bank, which is just south of the Falkland
Islands
and just north of 55°S. We have torn up every
net we put down, two of them irrevocably, too badly torn. We have been
using a weak link on the left side of the net towing bridle, which is
designed to break when tension on the net gets too high; it will save
the net. It has worked (that is, it breaks at 4200 pounds of tension)
on all three tows we have used it on, so although we did not get great
catches, we also did not ruin the net the first two times. The third time,
we got only the doors and the front part of the net back, while the last
2/3 was ripped off. We have quite a few spares with us, but we have to
be sure that we will have enough gear to last the next two months of work,
so we have quit trawling on the Bank. We are making arrangements to get
more spares and some chafing gear (heavier net to put outside our nets
on the bottom) in Stanley, on East Falkland Island, this Friday. We also
set ten fish traps at about 200 m (650 ft.) depth, but the hagfish and
amphipods ate the bait so we caught very little. We set them again just
after breakfast yesterday at 500m (1625 ft.) depth, and put the bait in
containers with much smaller holes so it cannot be eaten. We were going
to pick up the pots this morning but the weather is getting worse and
it's too nasty to recover them right now. It's blowing 25-30 knots and
the seas are building (we estimate the larger swells at around 15 feet),
so we're going to steam north to about 54° S, 56.5° W and look
at the bottom before setting an otter trawl to fish at 1500 m (4875 ft.)
depth. We hope the wind will drop later today so we can recover the traps.
Setting fish traps. Notice the weather is closing in...
To make our deep trawls we looked at the best available bathymetric chart of the Falklands, and concluded that we will first tow in a basin off to the northeast of the Bank; water there goes down below 4000 m (13,000 ft.) depth. We could fish to the south but the isobaths (that is, the lines of constant depth showing the topography of the bottom) are close together there, whereas to the northeast they are quite far apart. This means that to the south the depth changes rapidly, the slope will be relatively steep, and there is much more likelihood that the bottom will be rough and we are likely to lose or damage gear. To the northeast, we expect the bottom will be pretty flat, with comparatively deep soft sediment and few rocks. We don't know of any deep sampling in that area. It's real exploration. We have decided to make two tows there: one each at 1500 (4875 ft.) and 3000 (9750 ft.) meters depth. To reach 3000 m we will put out 6500 meters of wire (about 21,000 feet).
One of the
reasons why I wanted to come on this cruise is that from the start it
was planned
to make these deep tows in order to collect deep
water fishes. I want to catch some very deep water snailfishes, which
are known from this region down to at least 7200 m (23,400 ft.), but other
deep-sea fishes and invertebrates will also be valuable specimens. Maybe
we will get some specimens of "new" (previously unknown) species.
Trawls like these require substantial investments of time (= money) to
make, so few opportunities occur to do this. Even a 2000 m tow takes at
least 8 hours: time to put out 5000 m of wire at 30 m/minute, 15-30 minutes
to settle, two hours on the bottom, and time to haul the wire and the
net back. And we plan to fish in the South Sandwich Trench, which goes
down to 8250 m (26,812 ft.)! We have 10,000 meters of new 9/16" wire
on our biggest trawl winch, and will put out all but 1.5 wraps of it (each
layer of wire on the winch drum is a wrap) at our deepest stations, which
may allow us to reach below 7000 m. It has a breaking strength of about
30,000 pounds, but we hope not to approach more than half of that. Including
all the costs of running the ship, the scientific party, and the equipment,
towing deep is a substantial investment.
Black-browed albatross,
35" long with 88" wingspan, sighted south of the Falkland Islands
During the last week we have each learned about the others and their work and become pretty well organized. This cruise is extremely complicated because we have so many different projects underway, although they are all related in having the objective of learning more about the fish and invertebrates living here. It takes time for everyone to fit together, to be able to share samples efficiently to make the most of what we collect, and to decide how to work together in the most efficient way. It's kind of like putting a jigsaw puzzle together, only the pieces are people and work tasks, and as we change our plans to fit our sampling needs, we constantly reevaluate what to do next within the fixed cruise schedule dates. Now what we need is some good catches to provide fish for all the projects to work with.
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