Developmental Stages of Grass Carp (Ctenopharyngodon idella) eggs in the Sandusky River in 2017

Grass Carp Ctenopharyngodon idella was imported to the United States in the 1960s for research into its usefulness as a biocontrol agent for nuisance aquatic vegetation. Escapees and intentionally stocked individuals founded wild, spawning populations in the Mississippi River and tributaries to the Laurentian Great Lakes. USGS-led research on the Sandusky River, a tributary to Lake Erie, demonstrated spawning of Grass Carp in 2015. In 2017, sampling with ichthyoplankton nets in the Sandusky River produced thousands of fertilized eggs on four dates during two distinct spawning events. We used published keys to estimate developmental stage of eggs, which can be used in conjunction with hydraulic models to predict spawning and hatching locations and with genetic analyses to estimate numbers of spawning adults.