Don't perpetuate the myth that an immigrants name was changed at the port of entry by immigration officials. Do the research and investigate what actually happened.
It doesn't look like a coincidence... the belowhttp://search.ancestry.com/iexec?htx=View&r=an&dbid=...
that Ancestry shows a "Jeitz Jablonski" arriving in July 1913...in Philadelphia and if one looks at the manifest, it's obviously Fritz.
But again, changing names by immigration officials is a myth.