Effects of Adult Biomass and Environmental Conditions on Bigheaded Carp Reproductive Output

Abstract Bighead Carp Hypothalmichthys nobilis and Silver moltrix (hereafter collectively referred to as Bigheaded Carp) have spread throughout the majority of Mississippi River since 1970s. The current northern invasion edge in Upper (UMR) spans between Pools 14 20 because limited passage at Lock Dam (LD) 19. Mechanisms limiting adult abundance above LD19 are unknown but may be due part lack reproductive success influenced by environmental factors. Our objective was investigate how relative biomass river temperature discharge affect maximum annual larval production UMR using a Ricker stock-recruitment model. Adult (kg/h) estimated annually with boat electrofishing larvae were collected every 10 d May August 2014–2017 14–20 UMR. ranged from 0.0 880.9 kg/h, whereas densities 2,869.4 larvae/m3. After accounting for variability among pools years, most supported linear model indicated number recruits per spawner decreased increasing increased mean discharge. results highlight importance conditions reproduction along leading edges invasion. Management strategies that aim maintain low where is not yet occurring could help limit population increases via reproduction, reducing high (e.g., commercial harvest, barriers) result greater output