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Zooplanktivory by Alewives in Lake Michigan: Ontogenetic, Seasonal, and Historical Patterns
Author(s) -
Hewett Steven W.,
Stewart Donald J.
Publication year - 1989
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1989)118<0581:zbailm>2.3.co;2
Subject(s) - alewife , zooplankton , population , biology , predation , biomass (ecology) , population density , larva , ecology , fishery , bioenergetics , zoology , environmental science , demography , mitochondrion , microbiology and biotechnology , sociology
We extended a bioenergetics model of growth for the average individual alewife Alosa pseudoharengus to the Lake Michigan population of this species in the mid‐1970s. We used the model to estimate patterns of total consumption of zooplankton by alewives. About 10% of total annual zooplankton consumption by Lake Michigan alewives could be attributed to larval fish feeding during the first 40 d of life. Young‐of‐year and larval fish together accounted for 50% of total annual consumption by alewives. Typical adult (age‐3 and older) fish accounted for only 21% of total consumption. We evaluated the sensitivity of estimates of consumption by alewife larvae by using upper and lower bounds on metabolic rate and energy density of larvae. Total consumption estimates based on the low and high metabolic rates differed by a factor of 3. Consumption was relatively insensitive to energy density. Modeling a 29‐d, normally distributed spawning period versus a single‐day spawning period resulted in a 9% increase in total consumption from first‐feeding larvae to fall young of the year. Predation by the alewife population was strongly seasonal: 45% of total annual consumption occurred in August and September, and 73% occurred during July through October. The mean daily population consumption (for each month), expressed as a percent of crustacean zooplankton biomass, peaked in August and September at about 8% of biomass per day. Similar estimates for the mid‐1980s alewife population were greatest in August at 2.3% of zooplankton biomass consumed per day. We estimated potential consumption by the peak 1966 alewife population (ifsevere mortality had not occurred that year) at 20% of zooplankton biomass per day, which suggested that food limitation was one cause of the severe mortality that year.