Zooplanktivory in the Baltic Sea: a comparison of prey selectivity by Clupea harengus and Mysis mixta, with reference to prey escape reactions

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 216:191-200 (2001) - doi:10.3354/meps216191 Zooplanktivory in the Baltic Sea: a comparison of prey selectivity by Clupea harengus and Mysis mixta, with reference to prey escape reactions Markku Viitasalo1,*, Juha Flinkman2, Maiju Viherluoto1,3 1Department of Ecology and Systematics, Division of Hydrobiology, PO Box 17, 00014 University of Helsinki, Finland 2Finnish Institute of Marine Research, PO Box 33, 00931 Helsinki, Finland 3Tvärminne Zoological Station, 10900 Hanko, Finland *E-mail: markku.viitasalo@helsinki.fi ABSTRACT: We investigated prey selection by the 2 most important planktivores in the northern Baltic, the Baltic herring Clupea harengus membras L. and the mysid shrimp Mysis mixta Lilljeborg. We hypothesised that the intensity of prey selection by herring is positively related to prey size and that deviations from this relationship can be explained by prey escape capabilities. For the non-visually hunting mysids we assumed that prey size is less important than in herring and that escape capabilities of the prey explain a larger fraction of selectivities. To evaluate these hypotheses, we obtained selectivity indices for C. harengus membras and M. mixta from previous studies made either in the field (herring) or in the laboratory (mysids). We then quantified the escape performances of the 5 most abundant crustacean zooplankton species in the Baltic Sea by videofilming the plankters escaping from an artificially created water flow (siphon). As hypothesized, herring behaved as size-selective predators: prey selectivity rank was Temora longicornis > Eurytemora affinis > Pseudocalanus elongatus > Acartia sp. > Bosmina longispina maritima. In M. mixta, the selectivity rank was surprisingly similar, only the cladoceran B. longispina maritima was relatively more positively selected than in herring. Comparing the observed predator selectivities with the results of the siphon experiments allowed us to identify cases where the predators appeared to show Œtrue¹ positive selection for a certain prey (E. affinis) and where the selection was Œtruly¹ negative (P. elongatus). On the basis of these results we suggest that large-sized copepods are important food for both herring and mysids and that a hydrography-induced shift towards a cladoceran-dominated zooplankton community may decrease the food gain by Baltic herring. KEY WORDS: Prey selection · Escape reactions · Clupea harengus · Mysis mixta · Mesozooplankton · Baltic Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 216. Online publication date: July 06, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.