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MEPS
Marine Ecology Progress Series

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MEPS 628:141-153 (2019)  -  DOI: https://doi.org/10.3354/meps13114

Changes over three decades in feeding success of young American Shad Alosa sapidissima are influenced by invading zebra mussels Dreissena polymorpha

Eric T. Schultz1,*, Michael G. Smircich1,3, David L. Strayer2

1University of Connecticut, Department of Ecology and Evolutionary Biology, Storrs, CT 06269-3043, USA
2Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA
3Present address: Seton Hall Preparatory School, West Orange, NJ 07052, USA
*Corresponding author:

ABSTRACT: We analyzed the feeding ecology of young American Shad Alosa sapidissima over a 25 yr period in the Hudson River Estuary, USA, where population declines have been attributed in part to food web alterations associated with invasive zebra mussels Dreissena polymorpha. We hypothesized that feeding success was positively associated with the standing crop or abundance of lower trophic level organisms and negatively associated with indicators of competition for resources, including the grazing rate of zebra mussels. Based on reports of feeding by larval American Shad on zebra mussel veligers, we considered an alternative hypothesis that zebra mussels have had a positive effect on feeding success. To test hypotheses, we employed 2 metrics of feeding success: amount of material in the gut, and condition. Hypotheses were tested separately for 2 early life stages of American Shad: post yolk-sac larvae and postmetamorphic juveniles. In larvae, short-term feeding success was positively associated with chlorophyll a concentration and negatively associated with conspecific abundance. In juveniles, short-term feeding success was negatively associated with conspecific abundance. Condition of larvae was positively associated with chlorophyll a concentration and with copepod abundance; condition of larvae and juveniles was negatively associated with cladoceran abundance. Our results on feeding success generally support the inference of previous studies that zebra mussels reduced the availability of essential prey for early-stage American Shad, perhaps contributing to recruitment losses in the Hudson River population of the species.


KEY WORDS: Feeding ecology · Estuary · Larval fish · Juvenile fish · Invasion · Gut contents · Condition


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Cite this article as: Schultz ET, Smircich MG, Strayer DL (2019) Changes over three decades in feeding success of young American Shad Alosa sapidissima are influenced by invading zebra mussels Dreissena polymorpha. Mar Ecol Prog Ser 628:141-153. https://doi.org/10.3354/meps13114

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