CS17 Invasive Species
Date: Thursday, June 13, 2002
Time: 3:00:00 PM
Location: Sidney
 
WinklerG, Université Laval, Québec, Canada, gesche.winkler@giroq.ulaval.ca
Dodson, J, J, Université Laval, Québec, Canada, julian.dodson@bio.ulaval.ca
 
DIET AND FEEDING OF TWO CO-OCCURING MYSIDS IN THE TRANSITION ZONE OF THE ST. LAWRENCE MIDDLE ESTUARY, QUÉBEC
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The estuarine transition zone is characterised by a macrozooplankton assemblage dominated by two mysid species, Neomysis americana and Mysis stenolepis, and the calanoid copepod, Eurytemora affinis. Our interest focused on interspecific differences in feeding behaviour of mysids as important intermediate predators. In experiments, mysids were provided with a natural zooplankton assemblage (individual size > 63µm). N. americana, consistently preferred rotifers and veligers over nauplii indicating suspension feeding. Predation rates on the veligers of the exotic species Dreissena sp. and rotifers increased linearly with increasing initial prey densities. In contrast M. stenolepis rarely grazed on rotifers and veligers, but showed raptorial feeding on nauplii, copepodits and adults of E. affinis. M. stenolepis exhibited much higher predation rates on copepods than N. americana. These differences in feeding suggest that both mysids maintain a different position within the food web of the estuarine transition zone. Predation by N. americana might contribute to the decline in relative abundance of veligers (Dreissena sp.) across the transition zone and M. stenolepis seems to have a great impact on E. affinis.