Supplementing Newly Hatched Artemia
By Bill Vannerson,
with contributions from David Kawahigashi and Eric Lund
There was a discussion on several Internet email lists regarding supplementing newly hatched baby brine shrimp (BBS), Artemia, with vitamins or calcium. The results of that discussion brought two important points to light. One, hobbyists can supplement their BBS to add valuable nutrients to their fish, both fry and adults. Two, the power of the Internet can be a valuable resource.
Supplementing Baby Brine Shrimp
Supplementing live food is nothing new. Many hobbyists have been adding vitamins to their worm cultures before feeding to fish and, to a lesser extent, adult brine shrimp as well. The strategy is to have the supplement ingested by the food and then by the fish when they consume the food.
The debate on the mailing lists started when someone questioned the effectiveness of applying this technique to BBS. Would supplements added to the hatching water be ingested by brine shrimp nauplii and then consumed by the fish? Or would the supplement simply stay suspended in the hatching water without providing any additional value to our fish?
The answer comes down to whether or not newly hatched Artemia will consume the supplement. The answer is "Yes" — but not right away. Artemia are filter feeders, but they don't start feeding until after their second molt, referred to as the "instar 2 stage."
According to David Kawahigashi, the commercial fisheries have been practicing this for quite a while.
Supplementing nutritional components, such as vitamins or calcium, into live brine shrimp has been practiced by aquaculture hatcheries for around 10 years. This bio-enrichment or bioencapsulation of brine shrimp nauplii (instar 2 or adults) began using emulsified fish oils containing high HUFAs, or highly unsaturated fatty acids, for marine finfish and crustacean larvae. This "breakthrough" enabled the culture of many other new marine species to be developed (flounder, sea bass, tuna, ornamental marine species).
Why Supplement?
Eric Lund, researcher from the University of Wisconsin, Madison, explains:
Briefly, saltwater fish all require a fatty acid that is common in marine fish oils called DHA (docosahexanoic acid) in their diet. They cannot make it from precursors, so it must be present in their food. Freshwater fish have a limited ability to make DHA from a particular precursor fatty acid of the omega-3 variety (linolenic acid), but they too can grow and reproduce well on a diet that includes DHA.
Brine shrimp are a great food for all small carnivorous fish, but they contain virtually no DHA. Marine fish larvae fed only Artemia exhibit mass mortality a few days after they start feeding. Aquaculture operations get around this problem by adding an emulsion of phospholipids rich in DHA to newly hatched Artemia. The Artemia eat the emulsion (more of it also sticks to the outside of their bodies). The Artemia are then fed to the fish or can then be kept refrigerated for up to 3 days.
Enriching or bioencapsulation of Artemia is essential for marine fish, but not for freshwater fish. Then why bother at all? Eric further explains:
I do believe, however, for some delicate killies [and other freshwater fish] that experience high moralities before sexing out, that enriching Artemia may be of some benefit. Another tactic worth trying is to feed enriched Artemia to the adults for several weeks prior to breeding them. In other species, fish eggs with low levels of DHA generally have poorer survivorship to first feeding than eggs that are rich in DHA. Giving females a diet high in DHA allows them to put more DHA into their eggs. As you all know, weak and feeble killie fry can be the result of several factors, including inbreeding, bad water conditions, and improper incubation conditions, but poor parental nutrition may play a role as well.