Quality testing of fish tanks for polar cod

Text: Ingrid Wiedmann

Pic­tures: Camilla Svensen


Every­thing is pre­pared for the qual­ity test of the fish tank

High qual­ity fish tanks are essen­tial for live sam­ples of polar cod to keep the caging effect as low as pos­si­ble for sub­se­quent eco­tox­i­co­log­i­cal exper­i­ments. To ensure proper han­dling con­di­tions, 17 vol­un­teers of the Car­bon­Bridge project (http://site.uit.no/carbonbridge/) exam­ined the qual­ity of the fish tank (water tem­per­a­ture, tank size and depth) on 80.5°N, 15°E under the harsh con­di­tions in the Arc­tic Ocean. The fish tanks were found good in all aspect.


Qual­ity test­ing of the fish tank, accom­pa­nied by “King Neptune”



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The Beginning of our Long Term Experiment

By Mor­gan Bender

Chose fish care­fully, anes­thetize effi­ciently, tag tact­fully, mea­sure and weigh accu­rately, place promptly in tank, repeat 700 times!!


This was the lat­est progress on the long-term expo­sure exper­i­ment. Despite the 25 degree sun­shine bless­ing Kårvika, the bio­log­i­cal sta­tion on Ring­vassøya, Jas­mine and I have toiled inside in the cooled 6 degree sea­wa­ter lab. Over the course of 2.5 days, we have placed small rice grain sized PIT tags intraperi­toneally in 716 polar cod, which will be exposed to three dif­fer­ent doses of crude oil mixed with a diet of Calanus over the course of 6 months start­ing in the begin­ning of July. Ini­tial mea­sure­ments of length and weight were taken using a fancy fish mea­sur­ing board that com­mu­ni­cates with an antenna read­ing the tag inside the fish. The polar cod were admit­tedly quiet hardy and accepted the tags with­out much of a flinch in their sleepy state. IMG_1854These fish will be fol­lowed for changes in sex­ual hor­mone lev­els, growth, repro­duc­tive devel­op­ment, and energy, enzyme activ­i­ties, and PAH con­cen­tra­tions in select tis­sues. Most fish are in a post spawn­ing or imma­ture stage with many larger fish in a thin state. We selected fish for the exper­i­ment from the many hun­dred col­lected dur­ing Polar night cruise this Jan­u­ary based on size and con­di­tion, only “aver­age” sized fish with some “meat on their bones”. With 1000+ choices, we hope that our quick deci­sions dur­ing net­ting will bring us closer to an even sex ratio. DSCN2354Our final exper­i­men­tal design includes a few extra tanks than pre­vi­ously planned; an addi­tion con­trol tank was added to be fol­lowed more atten­tively with nar­rower inter­vals between sam­pling events, allow­ing us to time sam­pling of the treat­ment tanks uti­liz­ing base­line knowl­edge from our “pop­u­la­tion” in the lab. We have also included two tanks that will pro­vide infor­ma­tion on sig­nif­i­cance of tim­ing and recov­ery in the response to dietary crude oil expo­sure. One tank will not be exposed until after vitel­lo­ge­n­e­sis, a cen­tral stage in the devel­op­ment of eggs and the other tank will be switched from a high dose to clean food at this same point, thus giv­ing us infor­ma­tion about recov­ery of fish. Cur­rently all tanks are under a mid­night sun light cli­mate with 3 degree sea­wa­ter, these con­di­tions will change with the sea­son to ensure that fish receive the nec­es­sary envi­ron­men­tal queues to sig­nal repro­duc­tive devel­op­ment. With fish hap­pily set­tled in their new homes for the next six months, I start my next task– mak­ing 150 kilos of Calanus J-ello shots laced with crude oil! IMG_1865Mathilde and Mor­gan tag­ging the last 250 polar cod on the last day!!

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Polar cod embryotoxicity to crude oil water soluble compounds

Exper­i­ment Com­pleted: Three days ago, we com­pleted our exper­i­ment. It was not with­out a lot of work and some trou­bles on the way.

After a mass mor­tal­ity that seemed pretty much out of con­trol in all our incu­ba­tors and not at all dose related we were left with too few sam­ples. After barely a week of expo­sure (start of gas­tru­la­tion), we decided over a week-end (it always hap­pens then) to start from scratch again!!!

Not with­out a lot of doubts and ques­tions: Since our rock oiled sys­tem had been run­ning for a week already, con­cen­tra­tion is the water were already very diluted for this new start. Would we see any effects at all? Were we in such low lev­els that even sub-lethal effects would be tricky to see?

We needed to through away (well fix…) all the remain­ing eggs of exper­i­ment 1, to pre­pare the incu­ba­tors for the new batches. But the fish left in our tanks seemed almost all done with spawning…would we find enough of then for a new start? Were we going to throw all away and not get enough eggs and sperm?

We took our courage “under our arms” and just did it!

New strat­egy: Obvi­ously the egg qual­ity was very dif­fer­ent from female to female…basically spoil­ing all the incu­ba­tors if you mixed all the eggs of all avail­able females together. We thus sep­a­rated the eggs from incu­ba­tor to incu­ba­tor, hop­ing that at least some of the eggs would be of good qual­ity and not just die as soon as the devel­op­ment would reach a lit­tle more com­pli­cated stage than division…



And it worked, not with­out the (almost) loss of 2 out of 5 egg batches. But so far the data is really nice…not mor­tal­ity from the treat­ment, but clear sub-lethal effects (see fig). The pic­ture shows bach­e­lor stu­dent Antoine and col­league Mar­i­anne strip­ping polar cod on sun­day evening!

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The Fig­ure shows the larva from one batch of eggs (out of 5) at the end of the exper­i­ment (larva left after all pre­vi­ous sam­plings, etc). The blue bars are the per­cent­age larva free swim­ming in the incu­ba­tors, the red are those (still alive) mal­formed and lay­ing on the bot­tom of the incu­ba­tor. The num­bers on the bars are the total count of larva per incubator.

Click on this link and you will see the heart beat of our eggs: embry­otox



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Polar cod & Petroleum in a international meeting!

What is the sci­en­tific com­mu­nity doing these days in the Arc­tic? What are the chal­lenges and risks for Arc­tic ecosys­tems? What are the effects of petro­leum related com­pounds on eggs, larva, juve­niles and adults? Is the Arc­tic more sen­si­tive than other regions. We are cer­tainly not (yet) find­ing answers to these ques­tions… but by look­ing at a spe­cial Arc­tic fish — the polar cod– from all pos­si­ble angles, we hope to come a bit closer to the answers.

A fan­tas­tic oppor­tu­nity to share knowl­edge and develop new research ideas around this tiny but so impor­tant fish and the chal­lenges of man-made activ­i­ties in the Arc­tic. Click on the pic­ture to down­load the pre­lim­i­nary pro­gramme. Pass this on, every one is wel­come. If you would like to join, send an email to jasmine.m.nahrgang@uit.no

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2014´s most exciting experiment?

By Jas­mine

Yes­ter­day, we started one of the years most excit­ing experiment..the oiled polar cod embryo exper­i­ment!! I am right now start­ing my 15th hour at work for today (only an hour more than yes­ter­day) and the night is not over yet.… my sleep­ing bag is next to me just in case, but I do hope that I actu­ally can drive the 40km home to Tromsø in about 2 or 3 hours.


After the won­der­ful job Eka­te­rina and Mor­gan did, fish­ing polar cod in the Bar­ents Sea, the last few days have been punc­tu­ated by sleep­less nights won­der­ing whether our catch would spawn unex­pect­edly and thereby just throw away all our efforts to run an embry­otox­i­c­ity expo­sure in the begin­ning of February.

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The last few months, there has been a lot of peo­ple hard work­ing on the design of the study and the set up. The engi­neers at our bio­log­i­cal sta­tion have been doing a great job putting together incu­ba­tors and oiled-rock columns. The pic­ture above shows Mor­gan fill­ing the columns will oiled rocks, that Luca prepared.


Finally the ripe fish were just too ripe for us to dare post­pone the big day one week more: strip­ping and in vitro fer­til­iza­tion was on the timetable. The small group of Flem­ming, Luca, Mor­gan and myself spent much of yes­ter­day find­ing out what we may have for­got­ten for a suc­cess­ful start. We were both ner­vous and impa­tient. I spent quite some time draw­ing a scheme on how the fer­til­iza­tion would look like. How many eggs in that beaker, so much sperm into this vial … I drew the plan at least 4 times, just to make sure I new it by heart and it made sense.

Finally we started and it went just perfect.



Today, for the first time of my life, I saw fer­til­ized polar cod eggs, reach­ing the 2 cell cleav­age stage, and the four and now they are at 32 cells. They are so beautiful.…I feel like a mother.…sleepless nights tak­ing care of the newborn.

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Polar cod of the full moon

By Mor­gan Ben­der, Jan 25th 2014


Under a full moon in the midst of the polar night, I watch as ice­bergs from Kongs­breen dance around the float­ing buoys of our last bot­tom trawl for live polar cod. The result was mag­i­cal as much as planned and calculated.

Now three full tanks of Sval­bar­dian polar cod are slowly steam­ing aboard FF Helmer Hanssen to their new home in Tromsø. Col­lec­tion in Ripfjor­den, Bille­fjor­den, and Kongs­fjor­den aboard the polar night cruise from Jan­u­ary 5th to Jan 20th was suc­cess­ful. Trans­port to Tromsø has thus far been a gen­tle jour­ney; the sunrise/set on Bjørnøya was a wel­come sign of our south­ern progress.  How­ever, polar cod do not seem to enjoy the boat life of five o´clock cake and beau­ti­ful views as much as I do, so it will be nice to see them set­tled and curve the mor­tal­ity that is threat­en­ing future polar cod projects (my own Mas­ters included).


Most of the cod are ripe and ready spawn, I have my fin­gers crossed that they can wait a few more days until we reach Tromsø. It is quite impres­sive to see how much of their body cav­i­ties are ded­i­cated to gonads, mak­ing them look like pot-bellied baby sharks cruis­ing around the tank. Per­haps too much time with fish has let my imag­i­na­tion wander…


In any case, be pre­pared to wel­come hun­dreds (per­haps tens of hun­dreds) of polar cod to the POLARISATION team early Mon­day morn­ing when the FF Helmer Hanssen steams into the kai.



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A good start of a new year

By Eka­te­rina Korshunova

On the 2nd of Jan­u­ary Jas­mine called me and asked if I would like to join the cruise to Sval­bard to get live polar cod for her exper­i­ments in four days. I was pos­i­tively sur­prised and accepted the offer imme­di­ately. The cruise was led by Marit Reigstad and I was very happy to meet many nice peo­ple work­ing on her “Car­bon Bridge” project. I was also very glad that Sam would help me tak­ing care of polar cod.

We started our cruse from Longyear­byen on the 6th of Jan­u­ary and went directly to the North in order to cross the Atlantic cur­rent at about 810N. Unfor­tu­nately, there were some prob­lems with the instru­ments, and it took some time to adapt them to the cold. So Marit decided to go to Rijpfjor­den for polar cod in order not to lose the time. On the 8th of Jan­u­ary in the morn­ing we started trawl­ing. I expected the weather to be minus 20 degrees and wind, so I put on all the cloths that I had. The actual weather was quite mild and only minus 5 degrees, but this I found out after I went out­side. More­over, I was stressed to get as many fish as pos­si­ble and I did not really care how I looked like unless I saw this picture…


Yes, I looked like a ball, but I was warm and WE GOT POLAR COD! So, I and Sam were really happy!





Together with polar cod we got other fish species like had­dock, Atlantic cod, capelin, daubed shanny that we should dis­sect for stom­ach con­tent. The most dif­fi­cult part was to define all the species and to find the dif­fer­ences between polar cod and small Atlantic cod. But we were very lucky and got some help from the crew mem­ber Jan Roald.


We fin­ished the dis­sec­tion at 3 a.m. and were very tired. How­ever, in the night I could not sleep. It was a storm of about 20 m/s, and I really wor­ried about my polar cod, if they were ok in the tanks and would not swim away. Only in the evening the next day the storm was over and most of the polar cod for­tu­nately sur­vived it. I sent a pic­ture of a tank with fish to Jas­mine, and she wrote that it was very few fish and not enough for the exper­i­ments. So, Kongs­fjor­den was our next tar­get to get more polar cod.



On the way to Kongs­fjor­den we made a stop at Mof­fen to get some sam­ples of Ice­landic scal­lops from my PhD project. We used tri­an­gle dredge to take them from the bot­tom, and then we sorted them out from the sed­i­ments. I, hav­ing so many cloths on me, could do it only in the hor­i­zon­tal posi­tion. But I was still very warm and comfortable.


Almost all Ice­landic scal­lops caught at Mof­fen had huge amounts of bar­na­cles on their shells. The weight of the scal­lops with bar­na­cles was some­times four times more than with­out them.







13th of Jan­u­ary: Two days of the cruise left, but we still had about 200 polar cod in the tanks instead of 1000. Luck­ily, all the water sam­ples for “Car­bon Bridge” project were done and our small fish group (Sam and me) got a pos­si­bil­ity to trawl the whole night in Kongs­fjor­den until we got the desired amount of polar cod.

POOR PEOPLE who could not sleep that night because of our eight trawl­ing oper­a­tions… I am still very sorry. But we got only one trawl with polar cod. Our two tanks were full; how­ever, I did not give up get­ting even more in order to be sure that Jas­mine would be happy.

All our night trawls had dif­fer­ent fish species and lots of shrimps that we cooked and ate together with crew. Sam was happy as he got a lot of stom­ach sam­ples and made many fil­lets of Atlantic cod and hal­ibut for all his friends in Longyearbyen.

14th of Jan­u­ary: There was no more time to stay in Kongs­fjor­den. In the morn­ing Marit and I agreed to go towards Longyear­byen and try Bille­fjor­den as a last chance to get more polar cod. Thus, I had finally time to go to bed and sleep.

kat10In the evening the same day we approached Bille­fjor­den cov­ered with the sea ice. It was quite cold out­side, but we all were excited. We were def­i­nitely in the Arc­tic! Brrr…

In the night we got time to trawl again before com­ing back to the har­bor in Longyear­byen. Sam was really tired, and I decided not to wake him up when the first trawl came on the deck. I was alone with the crew and we were not quick enough. As the result, all the polar cod got frozen in the cod end. In the sec­ond trawl I was sure that we did not get any polar cod, I thought there were only small Atlantic cod and we threw the catch back to the sea. How­ever, when the crew mem­bers sorted shrimps for cook­ing they found only polar cod among the shrimps. These polar cod were not black as the ones from Rijpfjor­den and Kongs­fjor­den. They had a yel­low skin colour. But when I opened one of the fish and saw the big gonads, I did not have any doubts. It was polar cod! We filled our last tank with polar cod from Bille­fjor­den and in two hours we were already back in Longyearbyen.

It was an inter­est­ing and instruc­tive cruise for me. We did every­thing what we  were sup­posed to do. I would like to thank Marit Reigstad for a good orga­ni­za­tion and under­stand­ing all our pref­er­ences. I thank the crew mem­bers for the tech­ni­cal sup­port, main­te­nance of the tanks, trans­porta­tion of polar cod and the tasty shrimps that we cooked in the night. I thank all my nice and kind col­lo­quies who made this cruise won­der­ful and unfor­get­table. Last, but not least, I thank Jas­mine for giv­ing me the oppor­tu­nity to go on the cruise and start the New year so GOOD!


Pho­tos were taken by Rudi Caey­ers and Eka­te­rina Korshunova

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