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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