Lake Sturgeon (Acipenser fulvescens), a focal species for rehabilitation efforts, populations have become severely depressed across their range. Population growth hinges on reproductive success and their unique reproductive ecology complicates restoration actions. Many knowledge gaps exist on biotic and abiotic factors influencing egg fertilization success. Lake Sturgeon utilize a broadcast spawning strategy where gametes are freely expressed in a communal setting across a variety of environmental conditions to maximize reproductive output. There has been little research conducted to explore basic biotic (sex ratios) and abiotic (flow) influences on reproductive success with the dramatic shifts in adult population structure and altered environmental conditions at spawning locations. The objective of this study was to estimate egg fertilization success across a range of sex ratio and flow conditions. Gametes were collected from wild spawning individuals and transferred into a controlled laboratory setting. Mimicking natural scenarios, gametes were released in an experimental flume to test fertilization rates under combinations of two different flow regimes, high (0.55±0.01 m/s) and low (0.18±0.01 m/s), and three different sex ratios (males:females=1:1, 2:1 and 3:1). Sex ratio was predictive of fertilization but only significantly greater under a 3:1 sex ratio. Water flow was not predictive of fertilization success. These results improve the knowledge of basic conditions for reproductive success and effective breeding population structures which promote natural reproduction.
