anal fin ripped off?

[mayjong]

hey all-
last night i saw that one of the anal fins on one of my orange striped goby was gone. looked like it was ripped off, there is almost a hole where it was, with "meat" showing. doesn't look like it was chewed on, and ive seen -0- aggression in the tank...it is still eating, and there was no damage the day before. weird, not sure what could have done it. the rest of its tank mates are gobies and cardinals, with a pygmy wrasse and a couple blennies...i do have a maxi-mini nem... and a cleaner shrimp
live rock is all the same, ive had it for a couple years (shrimp? or other?)

cant really get a pic of it... any thoughts?

 

[mayjong]

looked again, it is the pelvic fin, not the anal.
very unusual. ive had the fish for a couple of months...

 

[humaguy]

I had the same happen...fish seemed totally unfazed at the time and thankfully has not had a related issue...not sure who did it, I think there must be an emerald or large hermit...