Zooplanktivory by Alewives in Lake Michigan: Ontogenetic, Seasonal, and Historical Patterns

Abstract

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.

Annual variation in biomass and the community structure of crustacean zooplankton over 5 years in Lake Toya, Japan

“…In Lake Michigan, larval and YOY alewives have been shown to account for 50% of total annual zooplankton consumption by alewives (Hewett and Stewart 1989). YOY herring (Clupea harengus) is also more important planktivore than the yearling in Baltic Sea (Rudstam et al 1992).…”

Prédation planctonique des deux principaux poissons fourrages pélagiques du Lac Saint-Jean :

“…Bioenergetics models (Kitchell et al 1977, Hewett andStewart 1989) are widely used to assess food ingestion rates in fishes.…”

“…Subadult stages may even potentially have a larger impact on zooplankton than adults (Hewett and Stewart 1989). For instance, larvae, young-of-the-year and yearling alewife in lake Michigan together ingested almost 80% of the total population's consumption of zooplankton (Hewett and Stewart 1989).…”

“…Subadult stages may even potentially have a larger impact on zooplankton than adults (Hewett and Stewart 1989). For instance, larvae, young-of-the-year and yearling alewife in lake Michigan together ingested almost 80% of the total population's consumption of zooplankton (Hewett and Stewart 1989). Since bioenergetics models developed for adult fish are not applicable to early life stages (Karjalainen et al 1997) and given that it is difficult to assess directly food ingestion rate by larvae and juvenile planktivorous fish because they feed on small particles (Wuenschel and Werner 2004), mass balance models appear to be an appropriate method to assess food ingestion rates during early life stages of fishes.…”

Feeding of Juvenile Twaite Shad (Alosa Fallax Lacépède, 1803) in the Elbe Estuary.

“…HEWETT and STEWART (1989) while investigating Alosa pseudoharengus in Lake Michigan stated that especially the age group 0 can contribute a large proportion to the populations total consumption. In that lake, young-of-the-year consumption amounted to about 50 % of the annual total consumption of this species.…”