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The most common technique for feeding shellfish is by monitoring water color. Simply add a dose of Instant
Algae Shellfish Diet to you tank and watch how long it takes for the animals to clear it. If they clear it
in less than 60 minutes, add more. The recommended schedule for juvenile and adult shellfish is 1-2 times
each day, but can be as little as once per week.
*** New Information as of July 1st, 2010 ***
Shellfish Diet feed per day (ml) = grams of broodstock meat (WET
weight) x 0.036
Shellfish Diet feed per day (ml) = grams of broodstock meat (DRY
weight) x 0.335
http://www.fao.org/docrep/007/y5720e/y5720e09.htm#bm09..3.2.2 - See section 4.1.2.2 Feeding broodstock and Section
4.1.2.3 Calculating food ration for conditioning.
Paragraph 3 - “Thus, a 3% ration for an adult of 0.75 g dry meat weight amounts to 0.0225 g dry weight of algae
per day.”
Finishing the calculations,
- The dry weight of Shellfish Diet is 8%.
- If the mussel meat dry weight is 0.75g per animal
- For an oyster this would be about an 8g meat (wet). If you meat density or meat size is
different, we will need to make adjustments.
- Your feed rate should be 0.0225g/animal per day (the quote above) >> 0.281ml Shellfish
Diet per animal per day.
- 300 mussels at 0.281ml/day = 84mls per day
- 84mls/day X 42 days = 3.5 liters of Shellfish Diet
- This amount needs to adjust upward (slightly) to account for algae loss in flow through
systems (see the next section)
*** Old Information ***
The most scientific information we have for determining feed amounts is from a study done in 1999 on post-set Crassostrea
virginica oysters. The study measured feed rates for two objectives: optimal food
conversion and optimal growth rate. The determination was that optimal food conversion occurred at 2% daily dry weight and optimal growth rate occurred at 5%.
For example, if you had 100 grams of oyster spat and wanted optimal growth rate you would feed them 5 grams of
dry weight algae each day. If you were feeding them Instant Algae Shellfish Diet which has a dry weight of 9% you
would need to use 55 grams of algae concentrate each day (5 grams / 9%). If you wanted optimal
feeding conversion you would use 22 grams of Shellfish Diet (2 grams / 9%).
You can also use this formula for broodstock conditioning but
you must first subtract the shell weight, leaving only the meat weight. For example, if you have 1000 grams of
broodstock and 60% of the weight is shell, calculate the feed for 400 grams of meat weight. You can also reduce
the intake to 1% of daily dry weight.
We strongly recommend using the Shellfish Diet
rather than a single food such as Isochrysis. A mix of algae will usually provide much better
results.
To download a spreadsheet that
will help you calculate the amount of each algae to feed, click here.
How to Feed:
For information about using Instant Algae please click
here. For best results use continuous feeding or in batch several times each day. Since
bivalve shellfish are filter feeders good aeration and circulation will improve feeding rates and keep the algae
well suspended in the water column.
Wikfors, G.H., J.H. Alix, M.S. Dixon, and B.C. Smith. 1999. Feeding rations
and regimes for post-set oysters, Crassostrea virginica, fed cultured microalgae in a land-based nursery. J. Shellfish
Res. 18, 279-280 (abstract).
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