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Journal of Plankton Research Vol.23 no.7 pp.659-669, 2001
© Oxford University Press 2001
Artemia Swarming—Mechanisms and Suggested Reasons
Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic And Atmospheric Administration,2725 Montlake Blvd E, Seattle, Wa 98112, Usa
Present Address: Akvaforsk—–institute Of Aquaculture Research As, N-6600 Sunndalsøra, Norway
The hypotheses are proposed that Artemia swarming may be attributed to either density, age, feeding, salinity or light regime. Subsequent tests indicate that swarming patterns were affected by light regime, age and salinity, and that some of the observed patterns may serve to facilitate foraging and respir-ation. Swarming as such was influenced by density, age and previous feeding, but seemed unaffected by availability of food and salinity. Swimming activity among young Artemia was higher inside swarms than outside, while activity generally decreased as salinity increased. It is further indicated that the horizontal distribution of swarms is affected by salinity and depletion of Artemia over time, while the actual generation of swarms is a result of predisposition as well as chance. It is also demonstrated that young Artemia swarm more readily than older animals and that there is a critical density for immediate swarm formation. The results imply that swarming may reduce the availability of enriched Artemia in larvicultures of fish, and that older Artemia form less coherent swarms than younger Artemia and therefore serve better as live feed.