First Evidence Of Grass Carp Recruitment In The Great Lakes Basin

We use otolith microchemistry, ploidy analysis, and aging techniques to assess whether four grass carp (Ctenopharyngodon idella; 451 – 514 mm) captured from the Sandusky River, Ohio were the result of natural reproduction within the Lake Erie basin.  Multiple lines of evidence indicate that these fish were most likely the result of successful reproduction in the Sandusky River.  First, at least two of the fish were diploid. Second, Strontium:Calcium (Sr:Ca) ratios were elevated throughout the otolith transect in all four grass carp from the Sandusky River. This reflects the high Sr concentration of the Sandusky River and indicates that these fish lived in a high-strontium environment over their entire lives. Third, Sandusky River fish displayed higher Sr:Ca ratio variability than fish from aquaculture ponds with stable water chemistry. Fourth, Sr:Ca ratios in the grass carp otoliths from the Sandusky River were lower in their 2011 growth increment (a high water year) than the 2012 growth increment (a low water year), reflecting the observed inverse relationship between discharge and  water strontium concentration in the Sandusky River.  We conclude that these grass carp sampled in the Sandusky River are most likely the result of natural reproduction within the Lake Erie basin.