ESTIMATION OF INVERTEBRATE PRODUCTION FROM PATTERNS OF FISH PREDATIONIN WESTERN LAKE SUPERIOR

We used bioenergetic models for lake herring Coregonus artedi, bloater Coregonus hoyi, and rainbow smelt Osmerus mordax to estimate consumpt ion of zooplankton, Mysis, and Diporeia in western Lake Superior for s elected years between 1978 and 1995. Total invertebrate biomass consum ed yearly ranged from 2.5 to 38 g/m(2) with nearly 40% consumed betwee n August and October in all years. Copepod zooplankton represented the largest proportion of biomass collectively consumed by the three spec ies (81%), although rainbow smelt consumed almost twice as much Mysis as zooplankton. Growth efficiency was highest for rainbow smelt (3.84- 16.64%) and lower for the coregonids (1.91-12.26%). In the absence of quantitative secondary production values, we suggest our estimates of predatory demand provide a conservative range of the minimum invertebr ate production in western Lake Superior during the past 20 years.