Growth of pike larvae: effects of prey, turbidity and food quality
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We studied experimentally the effects of turbidity and prey composition on pike larval growth and hypothesized that pike larval growth varies with turbidity and food quality. We reared the first-feeding pike larvae (Esox lucius) in laboratory tanks with (1) clear or (2) turbid water provided with zooplankton rations from (3) an inner and (4) an outer archipelago site. The sites differ in physical features, salinity, eutrophication status, zooplankton community structure and density. Pike larvae showed the highest weight increase in clear water with zooplankton from the outer site and the poorest weight increase in turbid water with zooplankton as prey from the inner site. Our fatty acid analysis revealed that unsaturated fatty acid levels were highest in the outer site. The relative percentage of copepods was also higher in the outer site. This study supports the hypothesis that turbidity weakens the ability of pike larvae to capture certain prey. Further, zooplankton community composition matters in turbid water, but is not a primary factor in clear water.
KeywordsPike larvae Turbidity Fatty acid Baltic Sea Zooplankton
We thank Tvärminne Zoological Station and Pirkanmaa University of Applied Sciences for facilities. H. Knuutila gave advice and assisted in the lab. S. Jónasdóttir advised us on how to analyse fatty acids. We thank the anonymous reviewers, M. Öst for discussions, and A. Vehmaa and A.-C. Utne-Palm for valuable comments on the manuscript. Funding from the Onni Talas Foundation, the Walter and Andreé de Nottbeck Foundation, the R & D Institute Aronia and the Academy of Finland (project no. 125251 and 255566) are greatly acknowledged. The experiment complies with the current laws of Finland and animal welfare was always respected. Permission was not needed by ethical committee (signed as 0-class experiment).
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