Climate Change and the Impact On Fish Species in the North

Perhaps nowhere are the readily observable effects of climate change more evident than they are in Canada's North.   It is relatively easy to see and measure the impact of rising temperatures on sea ice, coastal erosion, degradation of permafrost, and so on.   However, when it comes to cause and effect, the secondary impacts in the areas of biology, ecology and productivity are much more difficult to ascertain. Changes in these areas tend to be indirect, take longer to occur, and when they do, there are invariably a whole host of other factors, over and above climate change, that can come into play. The interaction of these other factors can confuse or obscure cause-effect relationships and can also result in more significant and severe cumulative effects, or in layman's terms, these interactions have the potential to make a bad situation worse..

It is the combination of considerations that occupy the interests of a number of Fisheries and Oceans Canada (DFO) scientists.  One such investigator is Dr. Jim Reist, who is a research scientist working out of DFO's science lab in Winnipeg in the Arctic Aquatic Research Division. For over three decades now he has studied northern and arctic fishes, and in fact leads the Climate Change and Arctic Fisheries Research Program for DFO.

One project Dr. Reist has been running is called "Colonizing Fish Species as Threats To, and Indicators Of, Ecosystem-Level Changes in the Western Arctic".

Through collaboration with First Nations and Inuvialuit fishers, among others, this project seeks to determine recent shifts in migrating fish species which may be colonizing the area, potential threats to native fish populations, and future vulnerabilities of those populations.

Dr. Reist points out that freshwater, anadromous (fish that are born in fresh water, spend most of their lives in the sea and return to fresh water to spawn), and marine fishes that were once geographically limited further south - now appear to be colonizing the western Arctic, possibly as a result of climate change. 

Major concerns include increased competition for - and within - essential and limited habitats, predation, diseases, or parasitism, all of which have the potential to affect abundance, distribution and genetic integrity of native fishes. 

Warming waters and new species moving north certainly can affect local ecosystems.  Dr. Reist:  "Changing productivities within ecosystems depend on many different interrelated factors of course.  On one side you've got these shifting distributions, some of which may be negative, in the sense they will affect or result in range contraction of Arctic species. On the other side you have the potential for new species colonizing an area as conditions ameliorate. Those new species potentially will present opportunities over time for additional fisheries and new harvests."

One of the challenges researchers have - which can undermine their understanding of productivity issues - is a poorly developed knowledge base.  The key to making conclusions about fish distribution is understanding exactly where species occur, why they occur in some areas and not in others, and what limits local distributions.  But of course for that information to be relevant and useful it has to be compared to similar data gathered over time. 

Dr. Reist elaborates:  "Unfortunately, when we talk about things like colonization we don't have the underlying baseline information from the Arctic in good enough form, or in sufficient detail, to really determine what's what.  A lot of the basic research of the wider program that I oversee is to understand the distribution and biodiversity that goes with it.  Who is where, why are they there, what limits them, and so on. With that sort of foundation we then take a step back and say okay who could be coming – and if they do come which species in the present ecosystem are vulnerable."

The current project is part of a decadal long perspective on the bigger program that Dr. Reist is running to essentially determine where things stand presently. To simply gather the existing information through either archival sources or going out into the field actually searching for the species takes some time.  "But", says Reist, "if we pick the recent past say - 1990 to the present as the time frame for a baseline - then we can say this is what is here now and we can start looking for the likely colonizers, as well as how and from which direction they might potentially come into the area.  Then we can establish whether or not some of these species are in fact new.  But that baseline work is a critical part of the puzzle."

As they have begun to examine in more detail their understanding of colonizing fishes, researchers have concentrated in three areas.  One is the potential for freshwater species coming northwards in the Mackenzie Valley, being investigated by Neil Mochnacz and Chantelle Sawatzky, two biologists in Dr. Reist's group. The second context is looking at anadromous species such as Pacific Salmon colonizing from the west from rivers in Alaska. The third aspect is understanding the potential for marine fishes from the North Pacific coming through the Bering Strait and colonizing areas in the Alaskan Beaufort Sea and then moving eastwards into the Canadian Beaufort Sea. Marine fish research conducted by Andy Majewski and others within the Beaufort Regional Environmental Assessment – Marine Fishes Project, led by Dr. Reist, is establishing the baseline marine fish distributions against which colonization by marine fishes may be assessed.

Dr. Reist:  "For the Pacific salmon anadromous colonization, for example, I have a graduate student (Ms. Karen Dunmall) from the University of Manitoba who has developed a very active program where the local fishermen are encouraged to contribute their catches to the project.  From there we can do a number of things.   For example, we can determine which species we are dealing with -- if the frequency of the catch of the individual salmon species is going up or changing, as well as establishing some biological baselines and parameters about the fish themselves that are showing up in the Mackenzie River system.  We hope to do some genetic testing to determine the origin of the fish.  To answer questions such as whether they are coming from the closest populations in Alaska or are they coming from further away?"

"In the best of all worlds of course, you want your studies not to be just backward looking, saying this is what has happened and why.  You want to be in a position of looking forward."

Dr. Reist: "In the final analysis we do want to be predictive; at two levels.  First, by knowing the habitat conditions we will be able to establish - or at least test - some level of predictivity associated with changing environments. The second aspect will be whether we see new species come in and go, or stay and colonize - what will the potential consequences be for native species in the area? And that's where the parasites, potential diseases and even outright competition or predation questions come in. We are trying to get to that level of prediction and that establishes, of course, the benchmark for future work."

When it comes to the predictive end of the scale, Dr. Reist thinks we may be a couple years off that ability.  But he is confident it will happen.  Already they are pretty certain of the candidate species that are going to come in and occupy areas of the Western Arctic and work is progressing regarding likely habitats vulnerable to colonization by some species.

Above all he believes it is critical to do this work now because the world and our environment - particularly in the Arctic - is and will continue to change in the future, likely more rapidly than ever.   As he puts it, "Our landscapes, literally and metaphorically, will be very different within the next couple of decades and they are changes we won't have any direct control over. There will undoubtedly be surprises, but the more work we do at the front end of the time scale, perhaps the surprises will be fewer and farther between.  Clearly the more we learn now, the better prepared we will be to address the changes that do in fact come our way."

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