Feeding Preferences of Omnivorous Gizzard Shad as Influenced by Fish Size and Zooplankton Density
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Date
1996
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Abstract
In Ohio reservoirs, larval gizzard shad Dorosoma cepedianum less than 30 mm total
length consume only zooplankton but frequently switch to detritus as they grow longer than 30 mm. However, in laboratory studies without detritus, gizzard shad longer than 30 mm consume crustacean zooplankton. To explore the composition of diets of omnivorous 30-100-mm gizzard
shad, we completed 1-h laboratory feeding trials with different amounts of zooplankton and detritus and quantified the diets of gizzard shad in reservoirs. In both laboratory and field, gizzard shad
ate primarily detritus but also ate zooplankton, consuming more as more became available, which demonstrates that this species is a facultative detritivore. In the field, zooplankton consumption
declined as gizzard shad body size increased. We believe gizzard shad maximize growth by supplementing their low-protein detritus diet with more zooplankton as more becomes available. With this strategy, omnivorous gizzard shad may compromise the potential for food web manipulations
based on the trophic cascade hypothesis in Ohio reservoirs.
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Keywords
zooplankton, detritus, Ohio reservoirs
Citation
Yako, Lisa A.; Dettmers, John M.; Stein, Roy A. "Feeding Preferences of Omnivorous Gizzard Shad as Influenced by Fish Size and Zooplankton Density," Transactions of the American Fisheries Society, v. 125, no. 5, 1996, pp. 753-759.