The St. Croix Artificial Upwelling System : growth efficiency of the brine shrimp Artemia fed a unialgal diet of the diatom Chaetoceros curvisetus Cleve (STX-167)



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Four populations of the brine shrimp Artemia were grown in continuous culture in the St. Croix Artificial Upwelling System at average densities of 11.9, 6.3, 5.5, and 2.8 Artemia per ml. The four groups were offered the same flow of a unialgal diet of Chaetoceros curvisetus Cleve (STX-167), resulting in different ingestion rates between the groups. The Artemia were harvested during exponential growth at 12 or 14 days. From nitrogen analysis data, the gross growth efficiency (K₁), net growth efficiency (K₂), food chain efficiency and nitrogen budget were calculated for each group. In addition, the growth rates and survival were determined for each population. The gross growth efficiencies for the 4 groups ranged from 56.4 to 62.1%. The food chain efficiencies ranged from 39.8 to 52.0%. These are among the highest reported in the literature for any marine organism, whether in a natural or man-made environment. Growth of Artemia was found to be directly related to protein-nitrogen ingestion and to the ambient Chaetoceros cell concentration. Most efficient use of available algae and Artemia cysts is realized when ambient protein-nitrogen concentrations are maintained at 1.8 to 2.1 μg at protein-N per liter; higher concentrations waste algae, while lower levels depress Artemia growth rates too severly