Reproductive biology of female shovelnose sturgeon in the upper Wabash River, Indiana

Summary Shovelnose sturgeon Scaphirhynchus platorynchus are commercially important, supporting a viable roe fishery throughout much of the Mississippi River drainage. We examined the reproductive attributes of stage‐5 female shovelnose sturgeon captured from the upper Wabash River, Indiana, from March to June 2004. Shovelnose sturgeon were collected using boat electrofishing and experimental gill nets, measured for fork length (FL) and wet weight, and sexed externally if possible. Size‐ and age‐at‐maturity, absolute and relative fecundity, relative egg size, and gonadosomatic index (GSI) were determined for 49 female shovelnose sturgeon (range, 601‐ to 858‐mm FL). Female shovelnose sturgeon reached sexual maturity at approximately 600 mm and age‐at‐maturity ranged from ages 6 to 12 (median age = 9). Relative fecundity ranged from 11 220 to 23 956 eggs kg−1 (mean = 18 156 eggs kg−1). Absolute fecundity ranged from 14 294 to 65 490 eggs female−1 (mean = 30 397 eggs female−1) and was positively related to FL (r2 = 0.76) and wet weight (r2 = 0.82). The number of eggs g−1 of ovary weight ranged from 72 to 170 (mean = 98 eggs g−1) and was negatively correlated with GSI. GSI values ranged from 9.4 to 27.2 (mean = 19.3) and were positively correlated to FL (r2 = 0.18). Our results increase our understanding of shovelnose sturgeon reproductive biology and recruitment dynamics and provide input for models to evaluate the effects of harvest on this species.