AQUACULTURE
"We must plant a sea and herd its animals ... using the sea as farmers instead of hunters. That is what civilization
is all about; farming replacing hunting."
- Jacques Cousteau
Aquaculture is the farming of aquatic plants, shells and fish,
it is the counterpart to agriculture, and humans have been keeping
aquatic livestock for 8000 years. Budj Bim, an UNESCO site in Victoria - Australia
is recognized as the oldest fish farming site in the world.
There, the indigenous Gunditjmara people cultivated floodplains into
a complex of channels and dams to keep eels, in this way they were secured an
all year supply of fresh fish.
The situation around the North Sea today is not so different to what it was
in ancient Australia. The last generation of farmers on the coast around the North Sea,
did their farming in spring and autumn, harvested seaweeds to feed their livestock
and went out to fish in the winter and summer depending on when the fish came in from open waters. In 1970 this changed with the invetion of fish cage nets, that
were first used in Norway to farm salmon. The shallow bays and lagoon around
the North Sea also has long traditions for keeping shellfish like mussels, scallops and
oysters. Shellfish farming has declined, but fish farming has skyrocketed and it now accounts for more than 50% of the fish we eat.
Like in argiculture, the threats posed on marine farming is predation, deseases,
escaped livestock and enviromental overload. Some of the harvested species are
also intrusive species and poses a theat to the ecosystem they are imposed in,
like the Pascific oyster that spreads and makes beaches inacsessible and the rainbow
trout that dilutes the genetic diversity of wild seatrout and salmon.
The fjords and lagoons on the cost of Faroe Island, Scotland and Norway make
it technically ideal for raising fish in. Fish cage nets in open water are controversial
but for different reasons in different countries.
Norway is the biggest producer of salmon, and one inherent vice is the large numbers of fish that escapes the net. In the first half of 2019, 280 000 salmon escaped in fjords that are home to estimaed 560 000 wild salmon. Interbreeding will result in a
lack of diversity between different stems of salmon.
The Faroe Island, with the same conditions along the coast as Norway is also
ideal for salmon, and in addition has no native salmon stem to endanger.
The problem posed on Faroe Island is that tourism has become a big buisness, and
tourists come to see dramatic unspoiled nature, so the floating rings of fish cages
are seen as visually pollution.
Kelp and seaweed
Kelp and seaweed has 600 different used, most of them are in pharmacy,
but it is also used for animal and human food.
Natural grown seaweed is the most common.
In 2018 Norway harvested 200 000 tonnes of wet weed,
Scotland harvested 30 000
and Denmark harvested 10 000 wet tonnes.
In total 240 000 T.
Handhavested seaweed
is used for human food
and few other things.
This careful method leaves
the root and stem of the
weed so it can grow back
within 1 year.
Seaweed is also grown
on ropes suspended
from bouys that together
makesup a vertical field.
When harvested these
ropes are hauled aboard
a boat and handcut.
This also makes for
a fast regrowth.
Kelp grows in deeper waters
and makes up great fields.
Kelp is trawled with a sled
at approx. 15m depth,
and the roots, stem
and leafs are ripped ut.
This means the same area
cannot be trawled for 5 years.
Fish farming
Salmonoids have four phases of life and are
in the last phase usually farmed in open nets the sea.
In 2018, norwegian north sea harvest was 1 354 480 T fish, Scotland harvested 150 774 T
and the Faroe Islands harvested 70 000 T,
in total 1 575 254 T.
Atlantic Salmon accounts for more than 90%, and the
other species are Rainbow Trout and Atlantic Char.
Scallops, mussels and oysters
Oysters are either grown on the seabed in shallow and warm waters,
or in nets that tumble in tidal waters to form the oysters and make them grow. They are usually harvested
when 3 years old.
Scallops are often grown in hanging cages where they filter the water for nutrients. Scallops grow rapidly after three years and are usually
harvested after 4 to 5 years.
Mussels can be grown on hard substrates in the intertidal zone,
but usually thick ropes are used for
convinience. The blue shell is ready for harvest after 1 year to 1 1/2 years.
Sidenotes
There are some exeptions to these methods of farming.
On the Thornton-bank in the Belgian north sea, mussels
are grown on the foundations of windmills to make use of
the safety perimiter around the park.
Becouse of the distance from the shore, these mussels
live in cleaner waters and contain 40% more meat.
Integral Multi Trophic Aquaculture, IMTA sites combine mussels,
macroalgae and fish farming to make a ecosystem where pollution from
fish pens are filtered though seaweed and mussels.
IMTA are tested in Scotland, Faroe Island and Norway.
Keywords
GMO
Habitat
SUMMARY AND CONCLUSIONS
To conclude on wether or not aquaculture in the North sea is sustainable or not,
is difficult and there is many things to consider and many sources of facts.
The silent knowledge of local fishermen is also considerd here.
SALMON FARMING AND SUSTAINABILITY
Atlantic Salmon travels vast distances during its life, from the river where it hatched,
out the fjord and across the whole North Sea to its feeding grounds north of the Faroe Islands.
When the reach maturity it return to that exact same place in the river to spawn.
This gives the salmon a great genetic variation, and subdivides it according to the river where
it belongs. It was wild salmon from various rivers in Norway that in the 70´s made the genetic
foundation for domesticated salmon. Fifty years of selective breeding har narrowed down the
genetic diversity in domestic salmon.
In the end of september 2019, 283 000 salmon escaped from Norwegian pens,
47 000 from Scottish, but salmon is considered non-native in the Faroe Islands,
therefore escapes are only seen as lost revenue, not as environmental threat.
For Scotland and Norway, the wild stock is declared ”in crisis”based on the numbers caught by anglers. Scootish anglers caught 37 000 salmon in 2018 and Norway fished 97 194,
the wild stock is estimated to be 560 000 salmon.
The great decline is due to heating waters that change the foodsupply, dams and other physical obstacles in migration routes and fish farming with its accosiated sealice and habitatual competition from escaped salmon. The Norwegian Environment Agency estimates that the numbers of escaped salmons are
five times higher than the reported number.
Considering the environmental impact of the salmon pens and the numbers of fish thats escapes in
comparison to the size of the wild stoc I would conclude salmon farming today is
not beeing done in a sustainable way in Scotland and Norway.
In the Faroe Island, salmon farming is less controversial, and agreed to be sustainable.
SEAWEED, KELP AND SUSTAINABILITY
The majority of seaweed and kelp is harvested by trwaling, that is the most profitable method.
About 1% is seaweed for human cunsumtion, the rest is used for animalfood and over 600 uses.
Mainly, the alginates (algae sugars) are extracted as they are good for controlling viscocity,
and is used by the dentists to make bite-impressions etc. 80-90% of the seaweeds weight is water,
and of the remaining dry seaweed, only 40% is actually used and the rest is tossed back into the sea.
Of the 240 000 T harvested around the north sea, ca. 200 000 is trawled.
This is beeing done in shallow fjords and bays, that are valuable habitat for small fish as the cod fry,
and it takes about 5 years to grow back. This method is controversial, but harvest by trawling is
only 2,5% of the annual growth.
Considering the relatively small amount beeing harvested and that re-depositing of seeweed poses
no known threat I would conclude that this industry is sustainable and has a great potential for growth.
