Ecological risk assessment of Grass Carp (Ctenopharyngodon idella) for the Great Lakes Basin

............................................................................................................................... V RÉSUMÉ .................................................................................................................................. VI 1.0 INTRODUCTION................................................................................................................... 1 1.1 SCOPE OF RISK ASSESSMENT .................................................................................... 3 1.2 THE RISK ASSESSMENT PROCESS ............................................................................. 5 2.0 PROBABILITY OF OCCURRENCE/INTRODUCTION ........................................................ 10 2.1 LIKELIHOOD OF ARRIVAL .............................................................................................10 2.1.1 Physical Connections ...............................................................................................10 2.1.2 Human-mediated Release ........................................................................................26 2.1.3 Laker Ballast .............................................................................................................35 2.1.4 Summary of Likelihood of Arrival ..............................................................................41 2.2 LIKELIHOOD OF SURVIVAL ..........................................................................................45 2.2.1 Grass Carp Occurrence in the Great Lakes Basin ....................................................45 2.2.2 Thermal Tolerance ...................................................................................................46 2.2.3 Food Availability .......................................................................................................48 2.2.4 Predators ..................................................................................................................51 2.2.5 Disease ....................................................................................................................53 2.2.6 Summary of Likelihood of Survival ............................................................................54 2.3 LIKELIHOOD OF ESTABLISHMENT ..............................................................................55 2.3.1 Spawning and Nursery Habitat .................................................................................56 2.3.2 Estimated Spawning Population Needed for Establishment ......................................62 2.3.3 Stock Required for Effective Recruitment .................................................................64 2.3.4 Survival of Early Life Stages .....................................................................................64 2.3.5 Summary of Likelihood of Establishment ..................................................................67 2.4 LIKELIHOOD OF SPREAD .............................................................................................69 2.4.1 Natural Dispersal ......................................................................................................69 2.4.2 Canals ......................................................................................................................72 2.4.3 Laker Ballast .............................................................................................................75 2.4.4 Human-mediated Dispersal ......................................................................................75 2.4.5 Summary of Likelihood of Spread .............................................................................76 2.5 SUMMARY OF PROBABILITY OF OCCURRENCE/INTRODUCTION ............................77 3.0 MAGNITUDE OF ECOLOGICAL CONSEQUENCES .......................................................... 80 3.1 VEGETATION .................................................................................................................82 3.2 BIRDS .............................................................................................................................87 3.3 FISHES ...........................................................................................................................87 3.4 ABIOTIC FACTORS ........................................................................................................88 3.5 PATHOGENS/DISEASES ...............................................................................................89 3.6 SUMMARY OF MAGNITUDE OF ECOLOGICAL CONSEQUENCES .............................90