Journal of Experimental Marine Biology and Ecology Ž . 261 2001 237–244 www.elsevier.nlrlocaterjembe Effect of light on the feeding rates of pelagic and littoral mysid shrimps: a trade-off between feeding success and predation avoidance Maiju Viherluoto a,b, ) , Markku Viitasalo a a Department of Ecology and Systematics, DiÕision of Hydrobiology, PO Box 17, UniÕersity of Helsinki, FIN-00014 Helsinki, Finland b TÕarminne Zoological Station, FIN-10900 Hanko, Finland ¨ Received 31 August 2000; received in revised form 26 April 2001; accepted 4 May 2001 Abstract It has been shown that freshwater pelagic mysid shrimps capture zooplankton at a higher rate in light than in darkness. This has been suggested to be due to facilitation of visual predation on evasive zooplankton prey. To test this hypothesis with Baltic mysid shrimps, and to see whether Ž . Ž . pelagic migrating and littoral non-migrating mysids differ in this respect, we compared the feeding rates of Mysis mixta and Praunus flexuosus on the copepod Acartia spp. As light conditions change radically from the beginning of summer to late autumn at the Baltic latitudes, we conducted the experiments during three different times of the year to determine if there was a seasonal response to light in mysids. The feeding rates of pelagic mysids were significantly higher in total darkness than in light. In contrast, the feeding rates of littoral mysids did not differ in the dark and the light in the three different seasons. The decreased feeding of pelagic mysids under well-lit conditions may be an adaptation to avoid visual predation by pelagic fish. In contrast, littoral mysids, which live in the well-lit layer throughout the day, do not show a similar response. The fact that light did not increase feeding in either of the mysid species indicates that these mysid species do not use vision in capturing prey, but rely mainly on mechano-reception. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Baltic Sea; Light conditions; Mysid shrimps; Trade-off; Zooplanktivory ) Corresponding author. Department of Ecology and Systematics, Division of Hydrobiology, PO Box 17, University of Helsinki, FIN-00014 Helsinki, Finland. Tel.: q 358-9-191-28756; fax: q 358-9-191-28701. Ž . E-mail address: maiju.viherluoto@helsinki.fi M. Viherluoto . 0022-0981r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0022-0981 01 00277-5