Artemia strains differ in size and nutritional quality, particularly in content of highly unsaturated fatty acids (HUFA).
In the 1980s researchers found that fish larvae feed strains containing more than 4 percent eicosapentaenoic acid (EPA) 20:5 n-3 yielded significantly better growth in fish than Artemia with less than 3 percent 20:5 n-3.
Recent research suggests that docosahexaenoic acid (DHA) 22:6 n-3 is more important nutritionally than EPA.
Premium quality Artemia (usually from San Francisco Bay) are higher in 20:5 n-3 (EPA), but are still lacking in 22:6 n-3 (DHA), which is the most important HUFA for marine finfish larvae.
These high EPA Artemia are not equal to HUFAenriched Artemia in terms of nutritional value, but are helpful in bridging the gap between rotifers and enriched day-old Artemia.
The premium quality Artemia with high hatching rates, small size and greater HUFA levels are relatively expensive and sometimes difficult to find in quantity.
As an alternative, a hatchery can purchase a commercial enrichment product to treat lower quality Artemia. Here is a simplified formula for Artemia enrichment.
Formula:
Ingredients
- 800 ml (27 fluid ounces) deionized water
- 160 ml (5.4 fluid ounces) cod liver oil or other high omega fish oil
- 4 raw egg yolks (Egg yolks can be substituted with soybean lecithin— 8 g or 5 percent of the weight of the oil.)
- 30 g (0.06 pound) unflavored gelatin
- 10 g (0.02 pound) vitamin premix, including E, C and B complex
- 1 g beta-carotene
Procedure:
- Dissolve gelatin in 800 ml (27 fluid ounces) boiled, deionized water and let it cool to 40 o C (104 o F).
- Mix the oil in a blender on the highest setting for 30 seconds while adding betacarotene.
- With blender on, add vitamins and egg yolks. Then add gelatin and blend for 90 seconds.
- Store the product covered in the refrigerator.
For use with hatching Artemia:
Use about 0.5 ml (0.01 fluid ounce) of the enrichment diet per liter of incubation water (assuming 2 g dry cysts per liter of incubation water). After 18 to 24 hours hatching time, add another 0.5 ml of the enrichment diet per liter 2 hours before harvesting. Harvest before Artemia become too large for fish larvae.
For use with hatched, separated Artemia (in seawater):
Use about 0.5 ml of the enrichment diet per liter of separated Artemia (assuming a density of 100 to 150 Artemia per ml) for not less than 4 hours. Aerate the Artemia/diet mix during the enrichment process. Cooling the water with ice may slow the rate at which the Artemia grow during the enrichment process if size is critical to the target larvae.
The drawback to this procedure is that Artemia grow very rapidly, metamorphose to second in star metanauplii, and can become too large for some fish larvae to consume. The recommended solution is to use premium quality, newly hatched Artemia for the younger stages and then switch to enriched metanauplii Artemia as food for older fish larvae.
There are a number of enrichment products on the market. Artemia Systems I.N.V.E. (Gent, Belgium), Aquafauna Bio-Marine Inc., and Sanders Brine Shrimp Company are among the companies that carry these products. A number of companies are producing algae pastes or concentrates that also can be used as food supplements for Artemia.
Most years the demand for quality Artemia is greater than the supply. Supplies may vary from year to year. The 2000 harvest at the Great Salt Lake was a record low in terms of quantity. Many companies teamed up to form associations to make their operations more efficient. One such association, called Utah Strategic Alliance, is a group of a dozen companies.
Artemia storage:
Artemia can be stored for future use in several ways. They will survive for several days in a refrigerator, but should be warmed up before using. Artemia also can be stored in the freezer, but this will kill them. An ice cube tray works well. Freeze them in 7- to 8-ppt saltwater for best results.
Decapsulated cysts also can be stored. For long-term storage, the cysts need to be dehydrated. Transferring 1 gram of decapsulated cysts into a saturated brine solution of 330 g salt to 1 liter water dehydrates the decapsulated cysts. Aerate this for 18 hours, replacing the solution every 2 hours.
After 18 hours the cysts will have lost about 80 percent of their cellular water, so the air can be cut, allowing the cysts to settle before being filtered. These cysts can then be placed in a container and topped off with fresh brine solution. Seal the container and store it in the refrigerator or freezer.
Cysts with 16 to 20 percent cellular water can be stored for a few months without a decrease in hatching rate. For longer storage, reduce the cellular water content to less than 10 percent.
Author:
Granvil D. Treece
