Just exclude this model using --exclude
option. Quote from docs:
The --exclude option may be provided to prevent specific applications or models (specified as in the form of appname.ModelName) from being dumped. If you specify a model name to dumpdata, the dumped output will be restricted to that model, rather than the entire application. You can also mix application names and model names.
./manage.py dumpdata myApp --exclude=myApp.Backup