Rotifer and Artemia are used for culturing larval fishes, but the supply for Artemia cysts are influenced by the weather in the producing places, and a rise in cysts prices have a strong influence on the culturing costs. So these days many hatcheries stop feeding Artemia in earlier days and start feeding the other natural feeds such as Frozen Copepods and Frozen Fish Eggs. Frozen Fish Eggs sold mainly are pacific cod eggs, but some hatcheries having adult red sea breams are collecting the floating eggs and feeding them instead. Fish Eggs are rich in n-3HUFA such as EPA and DHA and they are used as a supplement in the latter Artemia stage. Frozen Copepods are rich in Astaxanthin as well as DHA and EPA. The Frozen Copepods sold mainly are harvested in Taiwan or Arctic Circle. At first Frozen Copepods were used as a substitute for Artemia, but now Frozen Copepods are fed when both Artemia and compounds are available. On the other hand Frozen Adult Artemia is used mainly among aquarium fish breeders.

It is said that 2000 tons of Artemia cysts are annually used. The biggest producing place is Great Salt Lake (GSL) in U.S.A., and 90% of Artemia Cyst imported into Japan is produced there. Since 1996-1999 GSL had suffered from a poor catch (the reason was reported that the population of algae in GSL, the feeds for Artemia, had decreased because much snow-water drained into GSL). Especially 90% up hatching rate cysts were in extremely short supply and their prices had risen. So the old stocks, 80% up eggs, Chinese, South American, and Vietnamese eggs were sold. Some Russian eggs were packed in U.S.A and sold as U.S.A products.  
Great Salt Lake
We had been worried that natural Artemia cysts were drained in 2000, but actually both harvest and quality had recovered. Last year State of Utah Department Of Natural Resources Division Of Wildlife Resources reported in advance of the season opening Oct.1 that “Cyst count per liter 44. Ratio of females 2.5 female to 1 male. The females are not carrying eggs at this point in time. Salinity 11.25%. All of the above are positive, the only negative condition is the lack of algae in the lake.”  
Great Salt Lake

Diameter of Artemia cysts, and sizes and fatty acid profiles of larval Artemia are depending on the places where they are harvested. Recently many hatcheries are choosing the cysts to suit the fishes they are culturing. The GSL products which have stable quality are sold mainly, but Vietnamese products are also fed to the fishes having smaller mouth such as groupers. The average counts of GSL cysts are 280,000 cysts/g, their average length of Artemia nauplii right after hatching out is 600μ. On the other hand the average counts of Vietnamese cysts is 310,000 cysts/g, the average length right after hatching out is 450μ. So Vietnamese cysts are better for the fishes having smaller mouth than GSL ones.  
Regarding the fatty acid profile the cysts harvested in Bohai bay, China and Vietnam has more than 10% of EPA. Both cysts are harvested in artificially controlled salt lake (or the sites of prawn farms). The evaluation for Chinese cysts was comparatively low apart form containing EPA, and Chinese cysts had been used for prawn farming, but recently their quality has much improved since the processing technology of GSL was introduced. In fact the brokers in GSL purchased a lot of Chinese cysts when GSL were suffering from poor catch in 1999.
It seems that most of the fish hatcheries chooses 90% cysts harvested in GSL, but when Artemia prices rose extremely higher in 2000 various quality of Artemia cysts harvested in several countries were used.

Larval Artemia are enriched as rotifers in almost all hatcheries before being fed to larval fishes. Since it was found that n-3 HUFA enrichment is important to culture larval fishes, many enrich products have been introduced. The first enriching method was attaching fish oils or emulsified ones onto Artemia nauplii body. On the other hand recent method is feeding directly to Artemia after opening a mouth,
These days many hatcheries have been using shell-removed cysts. The advantage for using shell-moved cysts is removing dart and bacteria along with shells, which prevents fishes from diseases.