Asian Carp Ecological Plasticity: Are They Moving Targets?

Control and prevention of the spread of silver and bighead carp (Hypopthalmichthys molitrix and H. nobilis, respectively) are high priorities, especially given the threat of their introduction and establishment in the Great Lakes basin.  Extensive efforts are being made to predict when, how, and where introductions may occur and lead to successful establishment, including models based on published life history and ecology information for the species.  However, the great invasion success of silver and bighead carps undoubtedly reflects high ecological plasticity in both species, and increasing evidence of hybrid individuals and hybrid backcrosses across their current distribution may reflect the emergence of individuals even better adapted to North American waters than the parent species.  We have observed several heretofore unreported behaviors exhibited by Asian carp in the Wabash River, Indiana, that may have significant implications for efforts to model, control, and prevent the spread of Asian carp.  For example, we have detected evidence of atypical spawning activity as late as 21 July 11 without a concomitant hydrograph change.  In addition, Asian carp eggs were detected as far upstream as Wabash River Mile 390, at which point the river is ≈ 30 m wide, the watershed area is 4,579 km², and mean discharge during the month of sampling was 115 m³/s. Finally, Wabash River Asian carp have exhibited movements and habitat use inconsistent with those previously reported for the Illinois River.  Our findings provide information suggesting even greater ecological plasticity in these species than previously thought.