Conservation Biology of the Shovelnose Sturgeon (Scaphirhynchus platorhynchus) in the Lower Chippewa and Red Cedar Rivers, Wisconsin

The shovelnose sturgeon (Scaphirhynchus platorynchus) has declined throughout much of its range over the past century.  Although currently listed as S4 in Wisconsin, there are only two known breeding populations in the state: the lower Wisconsin River and the lower Chippewa and Red Cedar rivers (C/R).  Historically, S. platorhynchus was the most common game species in the lower Red Cedar, but has virtually disappeared from the waterway over the past 50 years.  We are testing multiple working hypotheses to understand causes of this decline, including the potential disruptive threat of cyanotoxins drifting from severe blooms in upstream reservoirs.  Here, we seek to gain a firm understanding of current reproductive patterns and present larval drift data from 2013 and 2015.  To date, no S. platorhynchus larvae have been detected in either river.  However, lake sturgeon larvae (Acipenser fulvescens) were documented for the first time in the Red Cedar River in 2013.  Future work will include controlled cyanotoxicity tests on S. platorhynchus larvae, biomagnification assays in adults, and molecular genetic work to estimate effective population size (Ne) and gene flow between the two breeding populations.