How much do Arctic char move between different rivers around the Cumberland Sound? And why should we care?
 
Do char move between rivers? Char in the Cumberland Sound is currently managed river by river because it is thought that there is little mixing between rivers. This is based on two major sources of information: 1) Inuit Qaujimajatuqangit (IQ; local knowledge) informs us that fish from different rivers differ in shape, suggesting no mixing. 2) Other fish of the salmon family (to which Arctic char belong) go back to their natal rivers to spawn and form distinct populations. However, research conducted at other locations in the Canadian Arctic suggests that char may be moving more than we previously thought. For example, a tagging study conducted in Cambridge Bay (Victoria Island) showed that movement between rivers is very common.
 
If char move between rivers, why do they still differ in shape? According to Inuit Qaujimajatugangit, fish from different rivers around the Cumberland Sound differ in shape. How could they remain different if there was a lot of mixing between rivers? The answer lies in the migration behavior of the char:
 
 
 
 
 
 
Char movement
Why does it matter if char move between rivers?
It matters to understand the movement of char between rivers for the management of the char fisheries. Right now, the rivers of the Cumberland Sound are managed one-by-one. In other words, the HTA and the Department of Fisheries and Oceans provide guidelines (for subsistence fishing) or quotas (for commercial fishing) for each rivers independently.
    Let’s look at an example from an imaginary situation. Say the HTA suggests to its members to reduce fishing on a stock close to town because catches have been diminishing there. Instead they tell the members to go fish at the next fiord over to reduce the pressure on the local stock. If many fish from the local fiord move to the next fiord every year, this management action will not be very efficient. Indeed, the fishery at the next fiord will still have a large impact on the stock they are trying to preserve, because many movers will be caught in the fishery.
    Understanding the movement of char is therefore crucial to devise management plans that will insure sustainable harvest of char.
The migratory behaviour of char
After spending some years in the freshwater as juveniles, char undergo annual migrations to the ocean to feed in the nutrient-rich saltwater. Feeding then ends in the fall when char migrate up-river.
    The char that had time during the summer to re-build their energy reserves will go back up-river to go spawning to their natal lakes. Some char, however, will not be ready to spawn and will simply migrate up-river to over-winter in freshwater. It is those fish, that are said to be resting, that studies have shown to be more likely to move between rivers. One of the goals of the present study is to determine if that is true in the Cumberland Sound.
The project - Learning about movement without tagging
The project I propose to do has two major goals:
 
1-    To determine if char move between rivers in the Cumberland Sound, and
 
2-    To determine if resting char are more likely to move than spawning char
 
To attain those goals, I will make use of methods that should allow the study of char movement without tagging. The method uses DNA, a molecule that is found in the cells of all living things, and every person or animal has unique DNA. This is why DNA is often used in police investigation: the identity of a criminal can be determined by looking at DNA he left on the crime scene. But, while everybody has unique DNA, people that are related tend to have more similar DNA: your DNA is more similar to your dad’s or your aunt’s than it is to mine. It is this last fact that allows researchers like me to use DNA to study the movement of animals. Indeed, all the fish in, say, Avataktoo lake are more related to each other than to fish from another lake, and therefore have different DNA.
     “But, you may think to yourself, you just said that the fish may all be mixing together. Wouldn’t the DNA from the different lakes all be mixed as well then?” And you would be quite right. This is why I needed to collect DNA from juvenile (young) fish from the lakes that have never migrated to sea, and that therefore cannot mix. Using those ‘pure’ samples, I can then compare the DNA of young char found in the lake to that of the adults fished at the mouth of the Fjords (see diagram). The adult fish that have different DNA from the young char from that lake would then be movers from somewhere else. And in many cases, DNA will also allow me to find out where that mover is coming from.
 
 
    Diagram explaining the method: In this diagram, the juveniles were collected in the lakes and the adults were collected in the Fiords. The DNA of the juveniles is different in the lakes. However, because some of the adults are movers from the other lakes, some of them have DNA that differs from the DNA of the juveniles. We can then tell where those fish with different DNA come from by comparing them to the juveniles in other lakes nearby.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
This could therefore explain why different rivers have different shapes even if there is a lot of movement: because the movers do not reproduce in the river where they move to, there is no interbreeding between the rivers and they maintain their different shapes.