Sleepy Cod (Oxyeleotris lineolata)
One of the most promising fish for future aquaculture. This fish has many qualities to give it all-round appeal as aquaculture species for the future.
- It has been argued that this species has the best eating quality of all Australian freshwater fish.
- Extremely easy to transport at high densities.
- High flesh recovery.
- Can be kept and grown in high densities.
- Never have muddy flavour.
- Early indications are that it will be unsuitable for pond grow-out situations, however it is ideal for growing in recirculating systems.
Click to see short video of our sleepy cod
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
- The Fitzroy/Dawson River strain, grow better than northern strain for aquaculture.
- Recirculating systems necessary for grow-out.
- Must be stocked at high densities.*
- 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.
- Placid and easy to handle.
- Fitzroy/Dawson strain genetically distinct from northern strain.
- Sleepy cod grow faster in tanks than in ponds
- Males grow slower.
- FCR 0.68-1.38
- Best above 26C. Below 22C not recommended, with problems below 18C**
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.
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.
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.
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.
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.
- 50 - 300 $1.85 each (Inc GST)
- 300 - 1,000 $1.65 each (Inc GST)
- 1,000 + $1.40 each (Inc GST)
Preliminary Results of Jade Perch Feed Trial
By Max Wingfield
Aquaculture Extension Officer
Please note that not all aspects of this trail can be reported on, at this stage, as the trial has only recently finished and much of the data collected has yet to be analysed.
With the recent development of jade perch farming as a significant sector of the Queensland aquaculture industry, the AAQ has been actively encouraging research on the species. There are a number of fundamental issues relating to fish husbandry and biology that need to be addressed in order to improve the efficiency of jade perch production.
One of the major issues identified by the AAQ is to establish some baseline information on jade perch dietary needs and to assess their performance using a range of existing aquaculture diets. Therefore it was decided to conduct a feed trial to begin the process of answering some of these rudimentary feeding issues. The research was undertaken by DPI staff at the Walkamin Freshwater Fisheries and Aquaculture Centre and was initiated in response to a request by the AAQ, who provided funding towards the study.
The experiment was designed to assess fish performance in terms of growth rate, food conversion and fat deposition when utilising each of five diets (table 1). The diets used in the trial were selected to provide baseline information on the ability of the fish to utilise a broad range of dietary formulations. Four of the diets that were trialed were commercially available aquaculture feeds. The fifth diet was a mixture of the other four diets and was included so that there was a fairly regular increment in the basic nutritional profile (protein, crude fat and energy) of the five experimental diets (table 1).
Table 1: Basic Nutritional profile of the Five Diets Used in the Experiment
Crude Fat (%)
Excluding GST & Freight
1) Ridleys Redclaw (pellet)
2) Mixed *1
3) Select Silver Perch (6mm)
4) Ridleys Native Fish (6mm)
5) Ridleys Barramundi (6mm)
*1 “Mixed” = 66.7% Ridleys Redclaw, 11.1% Select Silver Perch, 11.1% Ridleys Native Fish, 11.1% Ridleys Barramundi
The experiment was conducted over a three-month period from October 2001 to January 2002. Fifteen, 600 litre, tanks were used in the experiment. Each tank contained 10 fish with an average initial, individual, fish weight of 338g. Three identical, indoor, semi-recirculating systems (17% water replacement per day) were used. The three systems each consisted of five experimental tanks sharing a common biofilter. This infrastructure allowed for the experiment to be conducted and analysed as a randomised block design. The fish were fed to satiation during a 1-hour feeding period every evening. Fish were anaesthetised, weighed and measured at one-month intervals.
Water quality was monitored on a weekly basis throughout the experiment and water temperatures were electronically recorded every hour. All water quality parameters remained within a satisfactory range throughout the experiment and there were no major differences between treatments. Average daily water temperatures started at approximately 26.5 °C in October, and rose to approximately 30 °C in January.
All fish appeared to be in good health throughout the experiment and no mortalities occurred. At this stage of data analysis, the major findings of the trial relate to growth rate, feed conversion, cost of diet and fat deposition. Each of these aspects is discussed below.
Significant growth was recorded for all diets (figure 1), with average weight gain for the redclaw, mixed, silver perch, native fish and barramundi diets being 152, 244, 281, 286 and 306 grams respectively. Although the best growth rate was achieved on the barramundi diet, from a statistical perspective (p < 0.05), growth on the barramundi diet was not significantly different to the native fish diet or the silver perch diet.
Feed conversion ratios ranged significantly between the diets (figure 2), with the cheaper, less refined diets having much poorer feed conversion rates (FCRs) than the more refined diets (figure 2). FCRs for the redclaw diet averaged approximately 3.5, the mixed diet averaged 2.5, while the three commercial fish diets were not significantly different from one another, averaging approximately 1.7.
It is interesting to note that the FCRs for all diets increased (less efficient conversion) as the experiment progressed (figure 2). Such an increase in FCR is commonly observed in trials where fish have been held on restricted rations prior to the experiment and are then fed to satiation. As the fish approach optimal condition, and fat reserves, their growth rate and feed intake often decrease whilst their metabolic requirements remain the same, thus resulting in lower feed conversion efficiency. It is also possible that the nutritional quality of the diets may have deteriorated slightly over the course of the experiment, as all the feed was obtained just prior to the start of the experiment and then stored at 4 °C.
Note that feed consumption data for the redclaw diet is not available for the first month of the trial. Feeding practices had to be refined in order to minimise wastage of this diet, as the redclaw diet, unlike the fish diets,
was a sinking pressed pellet that disintegrated relatively rapidly in water.
Another method of looking at the results is to calculate the cost of feed required to achieve 1kg of growth for each diet (this calculation is based on FCR and the cost of the feed). The “feeding cost” results are shown in figure 3. It must be emphasised that this is not an exercise in modelling production costs, which include many other factors. Therefore this simple calculation does not indicate the overall economic merits of the various diets.
It can be seen that both the crayfish and silver perch diets have the lowest feeding cost, at around $1.70 per kg of weight gain. The feed cost of the mixed diet averaged $1.77 and the native fish and barramundi diets were $1.97 and $2.14 respectively. As was the case with the FCRs (Figure 2), the feeding cost increased as the experiment progressed.
Despite the major differences in the nutritional profiles of the diets (figure 1), the amount of fat stored in the body cavity of the fish (expressed as percentage of visceral weight, ie fat, liver and digestive tract, to total body weight) averaged 16% and did not vary significantly between diets. This is a very interesting result and confirms that jade perch are able to utilise the available fat and dietary energy sources extremely efficiently. It also indicates that the fish are probably capable of converting dietary carbohydrates into lipids and fats.
Fatty Acid Analysis
Samples are to be sent away for laboratory analysis in order to determine whether diet affects the amount of fat stored in the flesh (fillets), or the proportion of omega-3 fatty acids.
The three fish diets each averaged 41% flesh recovery (as a skinned boneless fillet), the mixed diet averaged 40% and the crayfish diet averaged 38%. These differences, however, are not statistically significant.
The results of this experiment are very encouraging and demonstrate that jade perch is a robust omnivore, capable of utilising diets of relatively low nutritional value with a high degree of efficiency. The growth rates and FCRs obtained on the commercially produced fish diets compare favourably with other fish species that have been the focus of many years of nutritional studies.
It should be noted that this experiment was conducted in clear-water tanks. Therefore, the fish did not have any opportunity to supplement their diets with the various food organisms that would occur naturally in ponds. As such there may be some differences between the reported results and what may be achievable under particular pond culture conditions. Furthermore, it must be stressed that none of the diets used in this experiment were formulated for use with jade perch. Therefore their performance in this trial is in no way an indication of the overall quality of the diets, or of their suitability for their target species. It is, however, fair to say that out of the five diets used in the experiment, the silver perch diet was the only diet that ranked favourably in terms of both growth rate and feed cost. This result is not surprising given that the diet has been formulated to meet the needs of silver perch, which is a related omnivorous fish, and is likely to have relatively similar nutritional requirements to jade perch.
Because this study is a preliminary study designed to evaluate a range of commercially available diets, it is impossible to make any specific comments on the exact nutritional balance that is required for jade perch. More intensive studies with balanced reference diets would be necessary to determine an optimal dietary formulation for jade perch. At this stage of industry development, however, the practical application of comprehensive nutritional studies is debatable, as feed manufacturers are unlikely to consider developing diets specifically tailored to the needs of jade perch until the industry is producing around 300 tonnes of fish annually.
The trial also shows that the amount of fat stored in the body cavity is not a simple function of the nutritional profile of the diet. Therefore, if attempts are to be made to reduce the amount of body cavity fat, it is now apparent that industry and researchers will have to investigate other aspects of husbandry and feed management. More information on fat utilisation and storage will be available when the fatty acid profiles of the flesh samples have been analysed. It is, however, important to note that, even with the relatively high level of body cavity fat, the filleted flesh recovery of jade perch compared favourably with other cultured species.
It is now clear that jade perch is a hardy, omnivorous species, capable of achieving rapid growth rates on relatively inexpensive diets. It is, therefore reasonable to assume that this species can be grown at a relatively low cost of production. Furthermore, while jade perch do accumulate significant stores of body fat, they are well suited to filleting and provide a high recovery rate of flaky, white flesh.
These findings support the position that jade perch is an exceptionally good species for aquaculture production. It must, however, be stressed that jade perch farming is still a very new industry which faces many challenges and uncertainties. In my opinion, the biggest current limitation to industry expansion is the lack of public awareness and mainstream market acceptance. These marketing issues must be addressed and overcome in order to permit jade perch production to develop to a level correlating to its biological potential.
"Review of Golden Perch Aquaculture at Walkamin."
This page contains extracts of information taken from the AAQ Conference 2004, presentation by Brett Herbert.
Profitable Aquaculture Systems
Queensland Department of Primary Industries
Freshwater Fisheries and Aquaculture Centre
- Three strains of golden perch in Australia.
- Most commonly grown and sold are Murray-Darling strain.
- The Fitzroy subspecies (Central Queensland) is darker than the M-D strain.
- The Lake Eyre basin species is longer and thinner, and is generally more silver than the M-D strain.
- As colour is important we tried making fish paler.
- Using kaolin clay or holding in dark conditions did lighten the colour.
- Over three days they darkened.
- A light coloured chill bin produced lighter coloured fish closer to wild ones.
- Lighter colour produced in turbid water.
- Aquaculture golden perch received a slight premium on wild caught when gill & gut taken into account.
- Market prefers cleaned fish.
- Lighter colour produced in turbid water.
- Market of up to 1000t/year. (Sydney/Melbourne), although recently 400T.
- Tank purging resulted in significant weight loss (10%) over one week.
- In pond purging (no feeding for four days) prior to harvest.
- All ponds sampled before purging started with at least three women involved each time.
- Fish which did not wean successfully die off after 10-20 days.
- Weaning success is usually 90-95%.
- Small fish (0.15g,19mm) wean as well as larger fish (0.5g,32mm)
- Grading does not appear to be strictly necessary.
- About 50% of fish will not perform in aquaculture.
- These fish do not eat pellet food but do cost in oxygen and ammonia etc.
- Sex ratios –males dominate (60%)
- Females split into two groups-ones that don’t grow and ones that grow.
- Body shape significantly different after 150g (♀ heavier).
- Female growth slower initially but catch up at about 6-9 months.
- Juvenile ♀ were more susceptible to handling stress.
- When an average size of 600g+ is achieved, pond is ready to harvest.
- Fish sizes will range from 350g to 1kg+ (90%>450g).
- This takes from 14-18 months.
- Grow out from 200g to market size is relatively quick.
- Temperatures >15° 100g per month is achieved, sometimes more
- Feed a sinking pellet, 40% protein.
- Monitor feeding closely-size, quality, regularity.
- Maintain water quality.
- Realise that only 50% of fish may grow, bank on 30%.
- Sample product before harvest! (Taste)