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Apr 4 - Mesoplegaic fish

RRS James Clark Ross

WEBPAGE

Update (4th April 2004)

Noon Position : lat 51 57.2 S long 49 58.5 W (292 nautical miles from Stanley)

Distance Travelled since Immingham : 25569 Nautical Miles

Air temperature @ Noon today : 8.4 degrees C

Sea temperature @ Noon today : 7.5 degrees C

The JCR this Week.

Heading back to Stanley, the cruise nearly over, with enormous seas as a result of 3 days of strong winds, the atmosphere on the JCR is subdued but satisfied. A lot has been achieved in the last 4 weeks, scientifically and practically. The prescence of Len Featherstone, a fishing skipper by trade and our trawling advisor has been a bonus to the science party, enabling them to successfully and safely trawl for fish. We also have Simon Berry and Neil Farnell on board, having dropped into Bird Island to collect them after their 2 weeks hard labour reconstructing the seal study area.

However, the Southern Ocean is beginning to drop us hints. Yesterday morning we were awoken by a strange sensation, which most of us swiftly recognised as the beginnning of a huge roll. I heard Tom, my neighbour crashing around as he frantically tried to dress and rush down to the engine room. Meanwhile the galley staff were hanging onto the breakfast, trying (and failing) to save both the crockery and the food. The entire ship awoke with a crash as she rolled 35 degrees to port and then 25 to starboard. The ensuing chaos was quickly tidied away, and breakfast was reassembled half an hour later.

However, the weather has continued in an impressive manner, with big seas and high winds. The ship has rolled and pitched, with alarming crashes and rattles. Walls of water as high as the foremast appear and roll under the ship, pitching her headfirst into the trough before the next wave. The feeling is like being in a lift or on a roller coaster: one minute you feel heavy and as if glued to the ground, the next minute gravity seems to disappear as the ship falls away.

CRASH! Click to enlarge.

A wave crashes over the bow. Click to enlarge.

The angry sea. Click to enlarge.

The Southern Ocean in a frenzy. Click to enlarge.

Fortunately for us, the science was more or less complete before the worst of the weather. Martin Collins, our chief scientist, has written a summary of this cruise's science and all that has been acheived.


Science Bit In The Middle: Mesoplegaic fish in the Southern Ocean .

by Martin Collins

That headtorch sir, suits you sir.Click to enlarge.

Martin Collins, PSO. Click to enlarge.

We set sail on March 9th from Stanley on this, the JCR's nominal 100th science cruise, with 23 scientists on board for a month in the Southern Ocean investigating the ecology of mesopelagic fish. Mesoplegic fish, particularly the lantern fish or myctophids play an important role in the Southern Ocean ecosystem as consumers of zoolplankton and as prey of penguins and seals. The focus of the cruise is an area to the NW of South Georgia (Fig. 1) that is an important foraging area for potential fish-eating predators such as seals and king penguins.

Transects.Click to enlarge.

The South Georgia and Shag Rocks shelf, showing the E-W acoustic transects and the Western Core Box transcts. Click to enlarge.

March is not always the best time of year to be venturing out into the Southern Ocean and conditions en route from Stanley to South Georgia did not auger well for the rest of the trip; strong SW winds whipped up a big swell, causing the ship to roll heavily and many of the scientific party to disappear to their cabins. However, by the time we reached the first of our transects, the weather had moderated and the science could begin.

For the first 10 days of the cruise we used a combination of acoustic transects and nets to map the distribution of fish and krill in a broad area between the South Georgia shelf and Shag Rocks. At the same time, our land-lubbing colleagues at Bird Island (BI) were placing satellite tags and time-depth recorders on fur seals and macaroni penguins to see where they were heading, and then analysing their diets on their return. Meanwhile, on the bridge wings and monkey island, Andy Black (Falklands Conservation) and Kate Cresswell (BAS) braved the elements to map the at-sea distribution of sea-birds, seals and cetaceans. Lizzie Hawker and Nathan Cunningham lowered the CTD at a series of stations on each transect to provide the background oceanographic information, while the “bongo boys” (Geraint Tarling and Andy Hirst) lowered their nets to investigate the plankton community (fish food!) of the top 200 m.

Lizzie. Click to enlarge. Nathan. Click to enlarge.
Lizzie at her desk in the UIC room.
Click to enlarge.
Nathan, data manager, film co-ordinator and part-time Alexei Syle impersonator.
Click to enlarge.

We used two nets to catch the fish that were detected acoustically, an opening and closing double-netted RMT 25 (Fig 2) and a new pelagic trawl. After a few teething problems with the pelagic trawl, a fish catching and processing routine was quickly established. The mesopelagic fish catch was dominated by myctophids, such as Electrona carlsbergi (Fig 3) and Protomyctophum choriodon, which is regularly consumed by the fur seals. The most interesting fish were quickly swiped by Liz White (Bristol University) who took them to the dark room to examine their eyes and explore their ‘visual’ ecology. The rest of the catch was quickly identified by Tony (“North of the South”) North and dissected by Nadine Johnson (BAS) and the fish crew: stomachs were removed for dietary analysis; brain, muscle and liver samples were taken for a range of studies including fatty acid analysis (Dave Pond, BAS) and pollutants and enzyme activity (Cathy Debier, Catholique Universite, Louvain). The little that was left of the fish was thrown over-board to our band of hungry followers- the albatrosses and petrels that follow us wherever we go.

RMT. Click to enlarge.

The 25 m rectangular midwater trawl being deployed from the deck of the RRS James Clark Ross. Click to enlarge.

Following the transects, three days of intensive work focussed on “hotspots” of predator activity, with the RMT 25 fished round the clock to look at vertical distribution patterns. The net, which was sent to 1000 m, brought up some weird and wonderful bathypelagic fauna, the highlight being a ceratioid angler fish, with its luminescent lure still intact. The Longhust-Hardy Plankton Recorder provided data on the plankton vertical distribution in the same layers.

E.carlsbergi- probably the best fish in the world. Click to enlarge.

Electrona carlsbergi: one of the common species of myctophid fish caught during the cruise. Click to enlarge.

With the “fishy” part of our cruise almost complete, we started work on some of the other cruise objectives. One ongoing project, funded by the Antarctic Funding Initiative, uses moored instrumentation to determine zooplankton abundance and vertical migration over the Antarctic seasonal cycle. Two moorings have now been collecting data for over 8 months, despite the constant threat of ice-berg collisions. We brought one of them on board for its 3-month service.

With the first mooring on board, we headed into Stromness Bay to calibrate the echosounder and also let everyone stretch their legs ashore. After heading round the coast to drop off Rob at the King Edward Point base at Grytviken, we went straight back out to sea to pick up the second mooring. Both moorings were redeployed within 24 hours, thanks to the hard work and efficiency of Doug Bone and Peter Enderlein and also to the continuing good weather. We kept our fingers crossed that it kept going!

Pete's Buoy. Click to enlarge.

Re-deploying the shallow mooring. Click to enlarge.

Next on the list was the Western Core Box (WCB), a survey that is undertaken three times a year to determine the oceanographic conditions NW of South Georgia and provide an index of krill abundance. Krill are the main prey of macaroni penguins, fur seals and mackerel icefish and the core box survey allow us to investigate both inter- and intra- annual variability in krill abundance. It is a 4-day effort in which set of transects are monitored with multi-frequency acoustics and an undulating oceanographic recorder during the daytime, and ground-truthed with CTDs and a range of nets (Bongos and RMT8s) at set points during the night.

Our run of good weather had to end sometime, so here we are, almost finished in the core box, but hove-to in 45 knots winds! Everyone is on edge, waiting for the opportunity to get the nets back in the water and catch more fish! We have three more days at our disposal for science, then its back to the bright lights of Stanley and the RAF Tristar home.

Fixing the A- frame. Click to enlarge.

Things don't always run as smoothly as we would like, and things do break from time to time. Last week the A-frame, the large stern gantry, developed a leak. Doug "the deck" and John Summers were called out to work up on the gantry to fix the leak. Click to enlarge.

Ooh aar me hearty. Click to enlarge. Tony, North of the south. Click to enlarge. Where's the pine cleaner? Click to enlarge.
Ryan Saunders, expert Krill TV watcher and moorings assistant.
Click to enlarge.
Tony North, Dave Pond, and our friend Themisto Gaudichaudii.
Click to enlarge.
Nadine Johnson, who makes sure the fish have eaten their breakfasts.
Click to enlarge.

It's not ALL about work....

Science over, it was time to let our hair down and celebrate. It started with a quiz, and sack racing.......

Sack race. Click to enlarge.

and some very odd head gear in the bar.....

The Russian by Peter Enderlein. Click to enlarge. The wigs of Eastwick. Click to enlarge.

Good Morning and welcome to Radio Sevy. Click to enlarge

Just a regular science meeting.
Click to enlarge.

and then everyone was sensible for a moment.....

End of Cruise Dinner. Click to enlarge.

The officers and scientists at the end of cruise dinner. Click to enlarge.

but it didn't last long....


A final thought ...

We say goodbye this week to 2 of our colleagues, friends and neighbours. Paul Clarke is off to college, to study for his "mate's" ticket, and Tom Elliott has been promoted to 3rd engineer on the other crew. They fly home on Tuesday for short holidays before starting in their new roles.

Clarkey in the crow's nest. Click to enlarge. Tom and the ladies. Click to enlarge.
Paul Clarke- it's no surprise he is being sent back to college!
Click to enlarge.
Tom Elliott, and the "ladies".
Click to enlarge.

Once again, many thanks to Pete Enderlein and Martin Collins for allowing me to use their photographs, and to all on JR100 for an excellent month.

Next week....... back to Signy and the islands..