The Vader Family of Prince Edward County, Ontario

I am researching the family of William Vader and Isabella Black. William was the son of Johannes Veder and Katrina Delang according to baptismal records in Bath, Ontario. Their names must have been Canadianized because in later records they are shown as John and Katherine Vader. Known offspring were Daniel, born 1799, David born 1801, Esther Ann born 1802, William born 1803, Garret birthdate unknown, and Paul born 1805. William states his nationality as German in some records. I would like to find out more about where Johannes and Katrina came from and how they arrived in this area.