Mysid and fish zooplanktivory in Lake Ontario: quantification of direct and indirect effects

Canadian Journal of Fisheries and Aquatic Sciences
By: , and 

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Abstract

Mysis relicta and planktivorous fish feed on zooplankton in Lake Ontario and form a trophic triangle that includes intraguild predation by fish on mysids. Thus, fish affect zooplankton both directly and indirectly. To evaluate the importance of alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), and mysids as zooplanktivores in Lake Ontario, we measured abundances and distributions, assessed diets, and computed mysid and fish consumption rates based on bioenergetics models. We further estimated indirect effects by comparing clearance rates given observed and potential mysid distributions. Estimated consumption rates varied widely with season and water depth and ranged between 2.6 x 10-3 and 1.3 gm-2day-1 for mysids and between 1.4 x 10-3 and 0.5 gm-2day-1 for fish, representing a daily removal of zooplankton of up to 10.2%-day-1 and 2.0%-day-1 by mysids and fish, respectively. Mysid planktivory exceeded fish planktivory in May and August, but fish planktivory dominated in October. Estimated mysid planktivory rates were 2- to 90-fold lower than the potential rate if mysids moved to temperatures that maximized their predation rates, suggesting an indirect positive effect of fish on zooplankton.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Mysid and fish zooplanktivory in Lake Ontario: quantification of direct and indirect effects
Series title Canadian Journal of Fisheries and Aquatic Sciences
DOI 10.1139/f06-156
Volume 63
Issue 12
Year Published 2011
Language English
Publisher Department of Fisheries and Oceans
Publisher location Ottawa, Canada
Contributing office(s) Coop Res Unit Leetown
Description 14 p.
First page 2734
Last page 2747
Other Geospatial Lake Ontario
Online Only (Y/N) N
Additional Online Files (Y/N) N