| Culture Characteristics of Arctic
Char
I have commercially raised Arctic Char at
various scales of production since the late 1980's. Over that time I
have raised the fish in flow through tank systems, ponds, net cages and
high level water recirculation systems. These experiences where a
learning curve that lead to development a workable system that
consistently produced commercial quantities harvested on a weekly
basis. The eventual design was based on high scale water recirculation
using groundwater and continuously reusing up to 95% of the entire
rearing volume. This system incorporated equipment to filter water and
manage wastes. Through development and refinement of farm management
and quality control plans antibiotic use was not required to control
disease. Fish disease was prevented by implementing a strict
biosecurity program and using only certified disease free stock.
Available
from B&B Freshwater Fish Farm Gunton Manitoba
Overview of Culture Results
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We have grown Char at stocking densities that
exceed the normal for rainbow trout or salmon in similar conditions. In
a properly designed and operated system this factor can lead to
increased production amounts per unit of rearing space. The high
density stocking characteristics of the species can allow the
production intensification necessary in controlled systems and provide
increased economy of scale.
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Char grow considerably faster at lower water
temperatures than most other fish species that I have had experience
with. This resulted in reduced cost associated with heating water
supplies during the winter months. Better growth can be achieved using
temperatures that would be less than optimum for other salmonid
species. I have had the best results using water temperatures 12-14 C
during grow out of table fish, 5-6C during egg incubation and from
7-10C during early rearing.
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I have obtained food conversion ratios (FCR)
of 1 to 1 using a system design and feeding plan developed by hands on
experience. This FCR reduced the operating cost and return on
investment. ( I suggest that beginners use a ration of 1.2-1.0 to
represent average conversions for Char under culture conditions for
overall planning purposes).
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Our Arctic Char have consumed food over
extended light cycles and even fed better during low light levels. I
feel that this attribute offers a tremendous bonus. It has allowed us
to use a near continuous feeding program and resulted in better
conversions, faster growth and less stress during feeding.
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I have found Arctic Char to generally be less
aggressive in their behaviour than rainbow trout or salmon. Char are a
schooling fish by their nature, oddly (it may seem) they are more
aggressive at lower densities. Aggressive behaviour expands energy that
can be converted to growth. There less health consequences from
incidents of flesh and fin biting or even cannibalism, that is often
associated with aggressive behaviour. I have found that Char actually
grow faster and in a more uniform manner at higher densities.
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It appears to me that pound for pound, Char in
my systems produced less ammonia (from the metabolic process) than some
other fish species. Reduction of un-ionized ammonia is a key
requirement to successful management of fish culture system. Elevated
levels of un-ionized ammonia can be very toxic to fish. Reduced
production of ammonia and lower culture temperatures helped make Arctic
Char more favourable to water reuse. Generally the higher the culture
temperatures are, the greater the amount of ammonia there will be in an
un-ionized (free) form.
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Our marketing efforts have shown Arctic Char
to be well perceived, and is considered a unique product offering good
appeal in seafood dining. Buyers generally feel that farm raised char
are consistent in their flesh colour, texture and size. Users of the
products are very happy with the year round availability that farmed
fish provides.
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Stock survival we eventually experienced for
Arctic Char from "fry size to market" is equal to that
encountered for trout or salmon. We have learned some interesting
things about Char culture leading us to select a better operational
design and fine tune the rearing protocols, thus improving our survival
rates.
The above isn't a scientific
or research publication. It represents a snapshot version of my results
with raising Arctic Char in a commercial aquaculture farm. I plan to
write more pages on this subject in the future.
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