Marron Feeding Rates
Some preliminary feeding advice for semi-intensive marron farming in purpose built ponds.
Feeding rates are based upon data recorded for demand feeding of 12 growouts at Pemberton over three years.The table shows a summary, as averages, of the actual feeding rates used at Pemberton for 12 months of growout for 0+ to 1+ year old marron and growon of 1+ to 2+ yo. There is now a Personal Computer programme which can be used to predict feeding rate (and harvest marron size and survival, etc) given stocked numbers and sizes of marron and mean monthly water temperature.
These feeding rates are expressed as percent body weight per day (%BW/day) or, and much more usefully, as grams per square metre of pond per week (g/m2/week). The %BW/day is an old "feeding by chart" method used for trout: water temperature from day to day was always favourable and constant or very predictable; nearly every fish stocked was surviving so the number was known on any day; and it was easy to subsample for mean weight of fish, which were uniform in size (graded). If these conditions and the biomass (hence mean BW) are not accurately known each day (which is the case with most species, particularly crayfish!), this method can lead to dangerous overfeeding and fishkill or underfeeding and starvation (negative production). Modern practice is to use some type of demand feeding (which can be automated for fish).
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| Figure One |
For these reasons we've adopted a crude method of demand or maximum feeding for marron, which has been very successful. In this method the crayfish are fed around the edges of the pond at sunset and the edge is examined next day for uneaten feed and the subsequent feeds are adjusted if necessary, e.g., as marked changes in demand occur with growth and water temperature change. A similar method is used in prawn farming. For turbid water, some feed on a removable fly wire tray (like a square drop net on a pole) will indicate the demand.
For the demand method you need a feed value to aim at. When we started growouts we used values as follows: for 0+ newly stocked at the start of the growing season at a few grams mean weight and at a density of 5/(per) m2 , the amount of feed was 5 grams/ m2/ week. The weekly feed amount was increased up to 35 g /m2/ week for 2 year olds at 100 gram and 3/m2, or about 3000 kg/ha. Really there is no need to be more accurate than to use values of 5, 10, 15, 20 25, 30, or 35.
Note that these feeding rates are not sustainable without daily paddlewheel aeration. In fact, the "demand" of feeding is an interaction between both the crayfish and the water quality; crayfish won't eat - "demand feed" - if the water quality is poor. For this reason demand feeding is often called " feeding the pond".
The grams/m2 weekly rate needs to be multiplied by the area of the pond, given that the crayfish are uniformly distributed over the whole pond. The value in grams/m2/ week = kilograms /week for a 1000 m2 pond.
We feed on five (working) days of the week, so the weekly amount is divided by five to give an amount for each of these days.
Note: feeding a larger amount once a week or at a longer interval is totally unacceptable for this more intensive farming.
The accompanying Figure shows a simple relationship (based on the marron pond data) for the annual increase in biomass of crayfish from stocking at 15 grams and 5 /m2 to harvest 12 months later and the total feed needed in a 1000 m2pond.
Note the following features: if too little feed is used (a common problem if there is no aeration) the biomass at harvest can be less than at stocking (75 kg here), i.e., there is negative production! The amount of feed corresponding to zero change (about 140 kg in the Figure) is that needed to just maintain the crayfish alive without growth and is called the maintenance ration (also includes spawn production). In reality this amount, as feed supplied, is less than actually occurs because there is an amount of natural feed in a pond which the value does not take into account. For ponds supplied with water from different types of sources, ie, groundwater, surface storage, river, etc, the input of organic material and nutrients adds to that from supplied feed and the additional amount from these sources varies considerably.
In summary, crayfish won't grow and survive in purpose-built ponds without considerable amounts of food and this rule is particularly true if you wish to operate ponds at the more intensive level of higher production. On an equivalent weight basis (ie, wet to wet or dry to dry) the usual rate of conversion to wet weight of fish or crayfish from dry weight of pelletted feed of 1:2, or so, is in these real terms about 1:10.
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Aug | Sep | Oct | Nov | Dec | Jan | Feb |
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Water Temp oC |
12.2 | 12.9 | 15.9 | 19.2 | 22.3 | 23.9 | 22.5 | |
| 0+- | Feed as % BW/day | 4.9 | 1.9 | 2.3 | 3.6 | 2.7 | 2.3 | 1.8 |
| 1+ | Feed as g/m2/week | 6.8 | 4.2 | 6.7 | 14.7 | 16.7 | 19.4 | 20.1 |
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Marron Biomass kg | 3.0 | 4.4 | 5.3 | 7.4 | 10.4 | 14.0 | 18.0 |
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Marron Mean Weight g | 4.7 | 7.2 | 10.0 | 13.0 | 19.0 | 26.0 | 35.0 |
| 1+ | Feed as % BW/day | 0.4 | 0.4 | 0.7 | 1.5 | 1.4 | 1.2 | 1.1 |
| 2+ | Feed as g/m2/week | 9.9 | 8.5 | 14.6 | 29.7 | 29.7 | 29.7 | 30.1 |
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Marron Biomass kg | 35.1 | 32.9 | 31.4 | 30.8 | 32.4 | 35.6 | 39.3 |
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Marron Mean Weight g | 81 | 85 | 91 | 95 | 104 | 114 | 126 |
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Mar | Apr | May | Jun | Jul | Aug | Total Feed |
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Water Temp oC |
20.9 | 16.8 | 13.4 | 10.8 | 11.8 | 12.2 | ||
| 0+- | Feed as % BW/day | 1.6 | 1.3 | 0.7 | 0.5 | 0.4 | 0.4 | |
| 1+ | Feed as g/m2/week | 22.1 | 20.1 | 12.0 | 9.4 | 8.2 | 8.1 | 73 kg |
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Marron Biomass kg | 22.4 | 25.2 | 29.5 | 30.6 | 31.2 | 31.5 |
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Marron Mean Weight g | 44.0 | 52.0 | 58.0 | 64.0 | 68.0 | 71.0 |
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| 1+ | Feed as % BW/day | 1.1 | 1.0 | 0.6 | 0.5 | 0.5 | 0.5 |
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| 2+ | Feed as g/m2/week | 32.0 | 31.2 | 20.3 | 17.8 | 16.5 | 16.0 | 110 kg |
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Marron Biomass kg | 42.9 | 45.8 | 48.0 | 48.0 | 47.4 | 46.4 |
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Marron Mean Weight g | 140 | 156 | 169 | 173 | 174 | 175 |
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