Winter light conditions profitable
Wild-captured Arctic charr farmed at land-based aquaculture facilities grow better if light conditions are adapted to suit winter, new research on environmentally-friendly aquaculture shows.
It is normal practice to provide farmed fish continual light so
they grow as rapidly as possible. However, wild-captured Arctic
charr have adapted to living in arctic conditions with little
access to food in winter.
As a result, scientists have tested if a period of darkness in
winter can further improve growth of Arctic charr. Senior Scientist
Sten Siikavuopio says the tests have produced extremely good
"We have followed Arctic charr over a one-year period. After a
period of winter light conditions, during which the fish had a
break from the continual light, the Arctic charr grew 30 percent
quicker than Arctic charr which received a continual supply of
Eating less - growing more
In late 2007 the Arctic charr experienced an eight-week "winter",
during which they received eight hours of light each day followed
by 16 hours of darkness. During this period, less feed was provided
as the Arctic charr had a smaller appetite.
Land-based farming of Arctic charr functions in a manner that the
amount of feed the fish receive depends on the amount they consume.
Animal technicians check how much feed has disappeared and adjust
the amount of feed the following day.
"This shows there are good reasons for Arctic charr farmers to make
savings on both feed and electricity by introducing a short
winter," says Siikavuopio.
Focus on environment
Environmental considerations play an extremely important role in
this project. The Arctic charr originates from the lake Altevatn in
Troms, where fish stocks out weight access to food.
It is advantageous to capture fish from this lake, as both the
captured fish and those remaining gain better conditions. In
addition, fish farmers require less time to produce Arctic charr
ready for sale.
After the Arctic charr is captured in Altevatn, it is taken to
VillmarksFisk's land-based facility in Bardu. VillmarksFisk is
alone in farming wild-captured Arctic charr. The company is also a
pioneer in Norway with respect to the utilisation of recirculating
aquaculture systems (RAS).
The tests about winter light conditions are part of a larger
research project on RAS headed by Bioforsk. The water pumped into
the fish tanks goes through a so-called bio filter before returning
to the tanks.
The bio filter contains bacteria which break down waste products
and, of extreme importance, the water is purified from ammonia. The
bacteria break the ammonia down to less damaging substances like
nitrate, which enables the water to be reused. Before the water
returns to the fish, oxygen and a little new water is added and
redundant CO2 is removed so that the level becomes normal.
Recirculating cold water
For the first time water as cold as 8 ºC is being
recirculated. It was previously believed that bacteria needed
warmer water to break down waste products. However, this research
project shows that they can also accomplish the task in cold
"The possibility of recirculating colder water provides better
conditions for farming of Arctic charr," says Siikavuopio. "Given
these results, it may be possible to farm other fish
The manager of OppdrettsTeknologi, Steinar Skybakmoen, says RAS is
stable and functions well.
"We have not experienced a single case of excessive nitrite levels.
The utilisation of recirculating aquaculture systems is a new way
to run aquaculture in Norway," he says. "This technology makes it
possible to farm fish virtually anywhere."
Inland land-based farming of fish has often involved problems with
disposing of the large amounts of water required to provide good
conditions for the fish. However, when the water is recirculated,
only small amounts of water return to the ground, which the soil
can cope with.
Waste becomes plant fertiliser
Yet another environmentally-friendly test has been conducted in
connection with the wild-captured Arctic charr project with a use
being found for fish excrement. This is separated as part of the
recirculation process and has been used with good success as a
This is a collaboration project between Bioforsk, Fiskeriforskning,
OppdrettsTeknologi and VillmarksFisk, and is being financed by the
Research Council of Norway.
Senior Scientist Sten Siikavuopio is continuing to improve the use
of winter light conditions for Arctic charr in a new joint project
with Akvaplan-Niva, VillmarksFisk and Kirkenes Charr. The new
project will also study the effect of winter light conditions on
sexual maturity and fish quality.
Senior Scientist Sten Siikavuopio, phone (direct) +47 77 62 90