DSC_9406  Grass carp (Ctenopharyngodon idella) introduced to NZ in the late 1960's for the purposes of aquatic weed control. They seem effective when in large numbers and in closed waterways. Originally from Eastern China and Siberia, it is thought unlikely they will be able to breed here as they have very specialised breeding requirements, utilising extremely long rivers, however there is some debate about this. To date a few controlled releases have occured around the North Island, mostly in the north *