Introduction to the Circumpolar World The marine environment #2 Hreiðar Þór Valtýsson, MSc in...

Introduction to the Circumpolar WorldThe marine environment #2

Hreiðar Þór Valtýsson, MSc in Fisheries BiologyAssistant Professor, Faculty of Business and Science, University of Akureyri

Director, the Fisheries Sciences Center at the University of AkureyriBorgir (2nd floor, office 228), Norðurslóð, 600 Akureyri

Tel.: 460 8920 (office)E-mail: [email protected]

Office hours: By appointment

mailto:[email protected]

Iceland and surrounding waters

NOR0173 Hreidar Thor Valtysson The web

• Situated close to the Arctic Circle in the North Atlantic.

• Right at the boundaries of the cold temperate and arctic zones

http://staff.unak.is/not/hreidar/index.htm



The ecosystem – water masses

INJFU03 Hreiðar Þór Valtýsson The web

The battle of the currents

• Productivity of the ocean around Iceland is high

• Biomass and biomass production high on all levels of the food chain

• Due to regular mixing of sunlit surface and nutrient rich deep water

• The mixing of the cold currents from the north and warm from the south increases this mixing

• However highly variable between years

http://staff.unak.is/hreidar/

http://staff.unak.is/hreidar/



Greenland halibut

Oceanic

redfish

Capelin

Herrring

Blue whiting

Blue fin tuna

Scallop

Shrimp

Lobster and

monkfish

Cod and haddock




The effects of warming

What will happen with a warming climate?

In general• Cold water (arctic) species mostly suffer• Intermediate water (Sub-arctic) species mostly gain• Warmer water species (temperate) species will arrive





Arctic species

Greenland halibut• The second largest predatory fish in

high Arctic waters• Mostly fished N and NW of Iceland• Low stock size• Warming or overfishing ???





Arctic species

Northern (or pink) shrimp• Invertebrate fisheries began in the

middle of the 20th century, initially on shrimp and lobster

• Shrimp fisheries mainly north of Iceland => cold water species

• For a time the second most important commercial species in Iceland

• Then a disaster ........





Arctic species

Northern shrimp and cod• The stock collapsed and the catch collapsed• Reason, warming trend in waters north of Iceland• However not directly the temperature• => more cod in the area north of Iceland (the shrimp can

actually well tolerate this temperature) but ...• => the cod eats shrimp• What about

• Greenland ?• Newfoundland ?





Arctic species

Scallop• Chlamys islandica – the Icelandic scallop• Important fisheries in western Iceland• Unexpected collapse of the fishery • Now no fishery ....... Why?• The climate became warmer but the scallop

is supposed to tolerate warmer waters !• Studies revealed a protists disease that

killed them• In normal (cold) conditions it is to cold for

the protists• It came with the warmer waters and wiped

out the scallop stock





Arctic species

Capelin• A small cold water species and very

abundant north of Iceland. • However spawns in shallow and

warmer waters off the south coast. • It is during these migrations that it

becomes the most important food for many other marine species in Icelandic waters

• Usually spawns at the age of 3 and then dies.





Arctic species

Capelin• Annual caches more than 1.000.000 t, almost as high as all other species combined• Even if it is a cold water species the effects of warming climate are uncertain as it

depends on warm waters for spawning• In previous warm periods it has simply shifted from spawning and spawned in the

waters north of Iceland. • We do not know if the stock was smaller





Sub Arctic species

Herring• One of the most abundant fish stock in the world when the stock is in good

conditions, probably the largest in the N. Atlantic• Fisheries very important for many nations throughout the centuries. • Was for a time the most important fish species in Icelandic waters• Most stocks did collapse due to heavy fisheries between 1965 and 1975


0

500.000

1.000.000

1.500.000

2.000.000

2.500.000

1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001

Cat

ch (

t)

Other nations

Icelandic catch




Sub Arctic species


Herring• Cooling climate also

to blame?




Sub Arctic species


Herring• The herring stock will probably increase

in size in northern waters if the warming climate will continue

• Given that the fishery is restricted• And diseases will end




Sub Arctic species

Cod• Economically the most important

species during most of the centuries, a valuable species per kg

• Since the stock is quite large and he fish is greedy it also has a great ecological impact

• Many stocks in the N. Atlantic• Historically the largest off

Newfoundland (now collapsed), Barents Sea and Iceland

• All around Iceland





Sub Arctic species

Cod• Main spawning grounds

(meginhrygningarstöðvar) are off the south coast

• Egg and larvae drift west and then north, occasionally also to Greenland

• Main juvenile grounds (meginuppeldisstöðvar) are off the north coast

• Main feeding areas after they are mature are where the cold and warm currents meet off the west and east coast





Sub Arctic species


Cod• Very small native cod stock in Greenland• During warm periods cod can however become very abundant

• new grounds open up• Due to larval drift from Icelandic grounds• Is self sustained during warm periods but collapses in cold• A large part of this stock migrates back to Iceland to spawn and stays there• Very good for the Icelandic

cod fisheries• Mainly because of that it

has been predicted that the cod stock in Icelandic waters will grow with warming climate

• Has not happened (yet?)




Sub Arctic species

Northern shrimp and cod• This relationship between shrimp and

cod now well known in many other areas

• These species just don't mix, you cannot have both in abundance

• Warming climate will (given that the cod stocks are not heavily overfished) drive shrimp stocks down or further north





Sub Arctic species

Capelin and cod• However ……..• The sub Arctic cod depends heavily on the arctic capelin as food• If the capelin stock will be reduced due to warming it will have adverse

effects on the cod stock• This causes great uncertainties on the fate of the cod stock because

warmer waters might either mean larger cod stock as cod in warmer waters generally grows faster (such as in the North sea) or it might mean smaller cod stock if the capelin stock collapses





Temperate species


The winners, Temperate species

Blue- fin tuna

Mackerel

Monkfish or anglerfish

Norway lobster






Summary if warming continues• Valuable species added to the Icelandic fisheries (temperate)

– Blue fin tuna– Mackerel

• Valuable species will increase in abundance (sub Arctic and temperate)– Herring (not in Greenlandic waters but might if warmer)– Haddock (not in Greenlandic waters but might if warmer)– Monkfish– Lobster

• Valuable species will decline in numbers (high Arctic)– Shrimp– Scallop

• Valuable species that are great uncertainties about (high an sub Arctic)– Cod (probably increase)– Greenland halibut (probably decline)






Norwegian and Barents SeasThe same species and the same consequences




Introduction to the Circumpolar World The marine environment #2 Hreiðar Þór Valtýsson, MSc in...

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