The GlobalArctic MOOC introduces you the dynamics between global changes and changes in the Arctic. This course aims to highlight the effects of climate change in the Polar region. In turn, it will underline the impacts of a warmer Arctic on the planet Earth. For human civilization, the Arctic stands both as a laboratory and a warning for human kind. Besides, this course gives course followers an understanding of the key challenges and pathways to sustainable development in the Arctic region. This course is unique as it gathers several world’s experts for the first time to speak about the Arctic. Their respective inputs from different academic perspectives and disciplines offer a relevant and complete assessment of the Arctic region and its connection to the rest of the planet. At the end of the day, the course intends to offer in full scope the keys to understanding as the Arctic plays as a mirror of the human and geological dynamics.
Arctic Fisheries in an uncertain future
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Do curso por École Polytechnique Fédérale de Lausanne
Global Arctic
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WEEK 2 Arctic resources and the quest for them
In this second week, lecturers will expose various types of Arctic resources. Indeed, this week will highlight different resources exploited (fisheries, mining and so on) and the rush for new ones including tourism and O&G.
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Matthias FingerProfessor
EPFL, ITPP, MIR, IGLUS Lab
My name is Franz Mueter and I'm an Associate Professor of
Fisheries at the University of Alaska Fairbanks.
In today's session, we'll be covering Arctic fisheries resources and how they may be
changing in the global climate change context
and how management deals with that uncertainty.
I will first briefly characterize the existing fisheries around the Arctic,
and then talk about how the latitudinal
gradients that we see in species richness and biomass can lead
to a northward expansion or what we call a
borealization of these areas as the temperatures increase.
Secondly, I'll talk about how changing
temperature conditions and less ice around the Arctic changes
the energy flows and food web relationships in
these areas and how that can affect fish populations and fisheries.
Then finally, I'll close with touching on some of
the management responses and how management deals with fisheries in an uncertain future.
This map highlights one of the definitions of the Arctic and
the currently existing large-scale commercial fisheries
occur almost exclusively around the edges of the Arctic,
which is also the area where we see some of
the most rapid environmental changes particularly in Northern Canada and Alaska.
The fisheries' landings from these areas are dominated by cod-like fishes,
flatfish, crabs, and other species.
In contrast, there are only very small subsistence fisheries on the Arctic shelves,
such as those North of Russia and North of Canada,
and there are no fisheries presently in the Central Arctic Ocean.
We can illustrate the prevalence of fisheries
around the rim of the Arctic by just looking at
Fishing Vessel Days by
marine ecosystem here as an approximate measure of the fishing effort in those regions,
and this shows that the largest fisheries occur on these inflows shelves
where warm waters from the south flow northward into the Arctic.
The Arctic fisheries harvests in combination makes up about 10 percent of global catch,
and about a third of that occurs in each of three regions.
One is Barents Norwegian Sea in Eastern Atlantic;
then the areas around the Faroes, Iceland,
and West Greenland; and then the Bering Sea primarily in the Eastern Bering Sea.
The differences between the density of fish in the southern part of
this area and the northern parts
of the Arctic shelves can be illustrated by looking at one transect,
for example here, from the Southern Bering Sea,
through Bering Strait into the northern part of the Chukchi Sea.
Along the transect, the biomass of fish decreases
substantially from about 50 to 2,000 kilograms per hectare in the Southern Bering Sea.
By a couple orders of magnitude to only about 0.5 to
2.5 kilograms per hectare in the Northern Chukchi Sea.
In addition, there's also a strong gradient in
species diversity between those two areas was
a lot more species in the south and far fewer species in
the north of Bering Strait in the Chukchi Sea in particular.
It's not surprising then that the large commercial fisheries really only occur
presently in Southeast Bering Sea where those high densities are observed.
In fact, commercial fishing in
both the Northern Bering Sea and in the Chukchi Sea is either restricted or
completely prohibited under US law at present until we
know enough about these fish populations to perhaps allow for a fishery.
So, as the strong gradients from south to north in
biomass of fishes in their species richness and of course in temperature,
we would expect that some of these more southern boreal species
will expand into more northern waters as these waters warm,
and we do indeed see evidence for
that borealization in both survey data and from model predictions.
For example in this figure here,
you see the estimated northward shift of about 45 species in
the Bering Sea in their center of distribution over a 25-year period.
These fish all shifted at different rates with some
shifting very far north and some of them even shifting to
the south was an average shift of about 31 kilometers
over that time period or about 12 kilometers per decade.
That shift is coincidentally about twice the rate of shifts that
have been observed in terrestrial environments in birds and insects, for example.
So the shifts are occurring at a faster rate in the ocean than on land.
So, secondly, I want to illustrate some of the changes in the water column that are
associated with ice either melting earlier or not forming at all in an area.
Usually in the spring when there is ice present,
the spring phytoplankton bloom occurs right after the ice melts in very cold water,
and because of those cold temperatures,
the zooplankton cannot grow fast enough to take advantage of that production.
So, they cannot take up the phytoplankton as fast as it is produced,
which means that a lot of that phytoplankton actually
sinks to the sea floor where it then
supports rich benthic community consisting of sea stars,
a number of little crustaceans,
crabs, mussels, and snails and other species,
as well as species that feed on those like diving seabirds or
marine mammals like walrus that feed on little crustaceans on the sea floor.
In contrast, if the bloom occurs in
warm water that is if there was no ice or it melts really early
and the water doesn't warm up and
start stratifying and producing phytoplankton until later in the season,
then much of that production can be
consumed by zooplankton because of the higher temperatures,
and much of the production stays in the water column and
feeds pelagic fishes in the water column,
as well as plankton feeding seabirds and plankton feeding mammals.
That has been observed in a number of areas around the Arctic,
and we also have evidence for increased pelagic productivity in the Pacific Arctic,
and that includes increasing abundances of zooplankton in the Chukchi Sea,
increases in some of the plankton feeding seabirds in that area,
and increases in the condition of
bowhead whales that feed on small zooplankton in the water column.
However in the South East Bering Sea,
we've seen other changes associated with the lack of
ice in the spring or a much earlier ice melt,
and those changes are really evident
in the zooplankton community where we've seen a shift
to much smaller zooplankton that are less energy dense,
have less fat content than some of the larger fattier zooplankton,
and therefore aren't as good as prey for
plankton-eating fishes or for plankton-eating sea birds or mammals.
As a consequence, we've seen some fairly dramatic declines in
at least two of the large commercial fish stocks in Alaska,
the Alaska pollock and Pacific cod that has led to a pretty drastic reductions
in fishing quotas were simplifications on the global whitefish markets.
So to summarize some of the things that we've been observing,
both observations in the field and model suggests the potential for an expansion of
the southern boreal fish communities towards and into the Arctic
whereas the two Arctic species are likely to retreat and actually decrease in abundance.
The observed expansion has largely occurred during summer feeding migrations,
and that's also when our surveys occur.
Whether these species can actually establish new spawning areas in the north,
remains to be seen and maybe limited by
winter ice conditions and very cold water in the winter,
as well as perhaps a lack of suitable spawning habitat.
So, who the winners and the losers in
this new Arctic will be as highly uncertain at present,
but some of the commercial cod species in the Pacific Arctic have already been
negatively affected which has resulted in large disruptions to some of the fisheries.
So, how can fisheries manager deal with this northward expansion of
fish and some of the associated management challenges?
A number of countries have already put in place
precautionary measures to prevent unregulated fishing in newly ice-free areas.
Most of these areas are actually in the exclusive economic zone which
extends up to 200 miles offshore from each country and
are managed separately by each country
or sometimes through intergovernmental agreements among countries.
So, the management in these areas really varies among countries.
In the US Arctic,
the US decided in 2009 to put the waters north of
Bering Strait off limits to commercial fishing for now
until we know enough about
the fish populations to make
an informed decision about whether we can actually open them to fishing.
There's also been a recent historic agreement that places
the Central Arctic Ocean off limits to commercial fishing for at least the next 16 years;
that was signed in November 2017 by nine nations and the European Union.
Thank you for your attention.
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