Could an Asian carp population establish in the Great Lakes from a small introduction

Bighead (Hypothalmichthys nobilis) and Silver carp (Hypothalmichthys molitrix) have established populations in the Mississippi, Illinois, Missouri and Maumee rivers, and because of the hydrological connections, there is now a risk that these species may establish in the Great Lake basins. It has been suggested this risk is minimal because of the small number of fish that breach containment measures, and possible mating-finding difficulties as a consequence. Using literature data, we parameterize a stage- and river-structured population model and examine the probability of a small number of fish establishing a population in one of the Great Lakes. We find that for sexual maturity earlier than age 5, there can be a significant risk of establishment with a very small number of fish ( 75 % probability) for a large number of scenarios involving a small number of founding individuals (<20 fish). We conclude that while propagule pressure does increase risk in this system, it is not the most important consideration. Instead, probable age at first maturity in a given Great Lake basin may be critical to determining risk.