Aquaculture of brine shrimp

Artemia breeding ponds, San Francisco Bay

Fish farm owners search for a cost-effective, easy to use, and available food that is preferred by the fish. From cysts, brine shrimp nauplii can readily to be used to feed to fish and crustacean larvae just after one-day incubation. Instar I (the nauplii that just hatched and with large yolk reserves in their body) and instar II nauplii (the nauplii after first moult and with functional digestive tracts) are more wildly used in aquaculture, for the reasons they are easy for operation, nutrients rich, and of small size which makes them suitable for feeding fish and crustacean larvae live or after drying.

Nutritional benefits

Since no artificial feed formulation is yet available to completely substitute for Artemia, feeding live prey to young fish and crustacean larvae still remains essential in commercial hatchery operation. The nutritional properties of newly hatched brine shrimp are high in lipids and unsaturated fatty acids (but low in calcium). Dried Artemia nauplii contain 37%–71% protein, 12%–30% lipid, 11%–23% carbohydrate, and 4%–21% ash.

The fatty acid compositions of the nauplii are highly environmentally determined. Also the nutritional quality of commercially available Artemia strains being relatively poor in eicosapentaenoic acid (EPA, 20:5n-3), and especially docosahexaenoic acid (DHA, 22:6n-3). Since these components are critical for the larvae development, it is common practice to feed this live prey with emulsions of marine oils that are rich in the EPA and DHA, which is referred as enrichment processes.

Industrial hatchery

Since the development of commercial marine fish culture in the late 1970s, the demand for Artemia cysts has gradually increased from a few tonnes to approximately 800 tonnes per annum, representing approximately 40% of the total aquaculture demand for feeds for early stages. The price of the cysts varies during the last a few decades depending on both demand and the quality of the cysts. During the last 25 years, the Great Salt Lake in the USA has been the major supplier of Artemia cysts to the world aquaculture industry and the subject of numerous speculations regarding its capacity to sustain a growing aquaculture industry. However, due to the unpredictable fluctuation of the cyst yield from Great Salt Lake, there are other sites for cyst production, such as lake Urmia in Iran, Aibi Lake in China, Bolshoye Yarovoye in Siberia, Kara Bogaz Gol in Turkmenistan, and several lakes in Kazakhstan.

Although hatchery process of brine shrimps are relative simple and easy to operate, a series of factors need to be controlled and monitored to make optimal use of the cysts. The critical factors are light, temperature, salinity, oxygen level, pH and cyst density, which vary between different Artemia strains. Hatching quality can be described by hatching efficiency (number of nauplii per gram of cysts), hatching percentage or hatching synchrony (time between first and last hatching cysts).

There are six stages in the hatching and development of Artemia industrial hatchery.

After hatching, and prior to feeding them to the fish or crustacean larvae, Artemia nauplii should be separated from the hatching wastes. After switching off the aeration in the hatching tank, cyst shells will float and nauplii will concentrate at the bottom of the tank. The nauplii are further concentrated in a concentrator rinse and separated from the cysts. The enrichment process, if needed, generally occurs after the nauplii develop a digestive tract. The three main enrichment approaches are listed below.