It is, and "RAS syndrome" (redundant acronym syndrome syndrome) should be encouraged, not avoided. "PIN number" is easier and faster to understand. Probably be

It is, and "RAS syndrome" (redundant acronym syndrome syndrome) should be encouraged, not avoided. "PIN number" is easier and faster to understand. Probably better understood than "PI number" or the expanded form. And in this case, a link just named "fish" would have been fairly ambiguous.