Mai is looking at tiny fish with big consequences

A small fish in East Greenland can influence the whole ecosystem and even affect humans.


By Nicoline Larsen 


Mai Apasiri Klasmeier is cutting up a polar cod at the size of 2 cm to take out its tiny little stomach. Then they open the stomach under the microscope and look inside. What has this little polar cod been eating?


You might wonder: Why is it important to know what a young fish from Northeast Greenland has been eating before it got caught? Because it can influence the whole ecosystem and even affect humans, says Mai Apasiri Klasmeier. Mai is a guest student at the Greenland Climate Research Centre under the supervision of Dr. Caroline Bouchard. They are working on their Master thesis about the diet of polar cod, specifically young individuals (the larvae).


“The polar cod plays a key role in the Arctic ecosystem,” Mai Apasiri Klasmeier tells Arctic Hub when we meet them in the lab at the Greenland Institute of Natural Resources. Polar cods are also known as arctic cod, eqalugaq in Greenlandic and polartorsk in Danish.


“Basically, the reason why polar cod is so important is that they are found all over the Arctic in high numbers. Many animals in the Greenland Sea ecosystem either eat them or get eaten by them.”


“The polar cod plays a key role in the Arctic ecosystem,” Mai Apasiri Klasmeier 


The polar cod is essential because they transport energy from the basic levels of the food web to the higher levels. Or, to put it simply: if they eat nutritious meals, they themselves will become nutritious meals.


The human eats the seal that eats the polar cod that eats the zooplankton (tiny animals in the water). But due to climate change and the warming Arctic, zooplankton species are changing. This means that the diet of the young polar cod might be changing. And this could potentially affect the whole Arctic ecosystem. So even though the fish is small, it can have significant consequences.


That is why Mai is cutting open the polar cods’ stomachs to find out what kind of zooplankton they eat. Do they eat ”the big ones that contain a lot of energy or the small ones with little energy”


Just to give you an idea about how small polar cod larvae and their food are: the fish range from one to three centimeters in length and their largest prey can be around 2000 micrometers – which is just two millimeters, barely the size of a pinhead!


Identifying the exact animal species the fish have eaten can be hard, as they are often very digested and fragmented.


Mai Apasiri Klasmeier will be finishing their master thesis at University of Tromsø. But we will keep you updated on their findings.


Mai Apasiri Klasmeier is a guest student at Greenland Research Climate Center. Hear them talk about their research into polar cod larvae in the video at the top of the page.