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Sleepy Cod Oxyeleotris lineolatus |
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One of the most promising fish for future aquaculture. This fish has many qualities to give it all-round appeal as a major aquaculture species for the future.
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It
has been argued that this species has the
best
eating quality of all
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Extremely
easy to transport at high densities.
Ø High flesh recovery. Ø Can be kept and grown in high densities. Ø Never have muddy flavour.
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Early
indications are that it will be unsuitable for pond grow-out
situations,
There are a few smaller growers who have already tried these fish for themselves with positive result. These growers have not had the benefit of having a blue print to follow.
In Asia there already exists a fish very similar to our Sleepy Cod.
It is known as the marbled or sand goby (Oxyeleotris marmoratus). Asian
sleepy cod are grown throughout South East Asia, particularly in
Malaysia, Thailand and Vietnam. They are the highest priced freshwater
fish in Asia, with farm gate prices of over AU$30 in Taiwan. Retail
prices in Malaysia and Thailand are around AU$45 per kg.
This fish
fetches some of the highest prices, (around four times that of Silver
perch) and is regarded as top quality. There is no doubt an overseas
market is out there just waiting for someone to meet.
Shipping
live, market sized Sleepy Cod, should prove to be relatively
unchallenging. They do seem to live up to their name, “sleepy” and
lay motionless in shipping bags. This means their use of oxygen is
minimal and therefore production of CO2 low. Many large fish should be
able to be packed in an absolute minimum amount of water.
Experienced
hatcheries have no difficulty producing fingerlings, however they are
one of the more time consuming
species
to produce, with a low larval to
fingerling survival rate, and therefore are an
expensive
fingerling.
If you intend to purchase fingerlings they should be ordered well before
the season begins to avoid disappointment.
The
picture at the top of the page is of a wild caught orange fish. This
orange form is extremely rare in nature. Research conducted by the
Walkamin Research Facility in Far North Queensland has so far not been
able to reproduce this colour in commercial quantities. All off spring
are brown until they reach approximately 120-150 mm. About 5% of
offspring have orange blotches, mostly about the head. Only 2-3% attains
full colour. This research has been suspended for the time being. Walkamin Research Facility also conducted growth trials so see if there were any particular populations of this fish that performed better as a grow-out fish. This preliminary work did show that the northern strain have a different appearance and are much stockier than the southern strain. Pond reared fish, at 200 mm, the northern strain was 163 gms, while the southern was 137 gms. However the population from the Fitzroy-Dawson* catchments, did grow faster in captive conditions, on artificial feeds. (Brett Herbert AAQ Conference 2001.) * The Dawson River flows into the Fitzroy River. The Fitzroy River flows into the sea at Rockhampton. This population is well south of the nearest northern populations.
Summary
of research as presented by the research scientist
Brett Herbert, at the AAQ Conference 2001
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The
Fitzroy/Dawson River strain, grow better than northern strain for
aquaculture.
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Recirculating
systems necessary for grow-out.
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Must
be stocked at high densities.*
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High
fat diets, (15-20%) undesirable as the fat damages the liver, this will
affect FCR because the liver is an important part of the digestive
system.
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Placid and easy to handle.
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Fitzroy/Dawson
strain genetically distinct from northern strain.
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Sleepy
cod grow faster in tanks than in ponds
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Males
grow slower.
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FCR 0.68-1.38
Ø
Best above 26C. Below 22C not recommended, with problems
below 18C**
Notes: STOCKING DENSITIES.
The
Murray cod industry is generally working in the 50-150 kg/m3 range (ie
min-max density). We believe this is a good guide that should be
followed for sleepy cod. It must be stressed, that many of the good
operators, (Murray cod growers) are using oxygen generators to increase
DO saturation to above 100%, this, along with high densities, is part of
the recipe to successful growing of cod in general.
TEMPERATURE They are very temperature tolerant. We have recorded temperatures in our ponds with brood fish, and small fingerlings, as low as 9c and as high as 35c. (We do not recommend handling them at low temperatures.) At Ausyfish we routinely have broodstock in ponds during winter at temperatures as low as 14C and sometimes as low as 11C. During these cold times we are not able to handle these fish and do sometimes experience some minor losses. At temperatures above 14C we do not experience any difficulties. We only stock Fitzroy/Dawson strain. They are very hardy and handle well, but do not handle well if temperatures are below 18c. Transport is easy as they live up to their name, "sleepy cod," and sit motionless in shipping containers. This results in low oxygen demand, and low ammonia production. Packing densities are still to be researched, but they should be very economical to ship live, packed densely, with a minimum amount of water. WEANING Fingerlings are easily weaned. Our fingerlings are not weaned as we believe it is better to ship the fingerlings soon after harvesting when they are in peak condition. They are raised in plankton ponds where they feed on natural food. We also believe that when weaned, then shipped, the stress results in a loss of confidence by the fingerlings in eating artificial food. They then need to be re-trained on to artificial food. The natural diet of sleepy cod is carnivorous. They feed on fish, freshwater shrimp and freshwater crayfish. They will therefore do best on a high protein diet similar to barramundi. Click here for information about weaning Sleepy Cod COLOUR The colour of sleepy cod can change according to environmental conditions. No research has been conducted to determine how to manipulate their colour but it will be possible to provide fish to the market in a preferred colour once some trials have been carried out. Temperature and light will most probably be the factors that effect the fishes colour. They are capable of changing colour within a few minutes. Below are some examples of their ability to display a range of colours. These fish were all taken from the same pond at the same time.
Click for more pictures of Sleepy cod CULTURE METHOD The sleepy cod is not suitable for free-range pond culture as they are highly carnivorous and cannibalistic, as well as very territorial. They are able to eat other sleepy cod fingerlings up to half their size. It is necessary to grade fingerlings regularly. It is also possible for the fish to stop feeding on the artificial diet if they are in an open environment. Ausyfish can supply fingerlings from about January produced from the Fitzroy/Dawson strain. Fingerlings are a minimum of 4cm and can be shipped to most major cities world wide. Ø 50 - 300 $1.85 each (Inc GST) Ø 300 - 1,000 $1.65 each (Inc GST) Ø 1,000 - 1,500 $1.30 each (Inc GST) Click here for shipping information.
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Click for more pictures of Sleepy cod
