One person was attacked on the genitals by a pacu in New Guinea prior to 2001; and possibly others have been attacked on other parts of the body; c.f. the last page of this July 2001 newsletter from the New Guinea Fisheries Department (via waybackmachine; a broken link to this appears in the relevant Snopes article). There is no indication in this report that the testicle was detached.
With regards to local newspaper
reports that people are being killed by
the Pacu Fish, the investigation has
revealed the following;
- Within the area between Korogu
village and along the Sepik River
to Wagu village (up river from
Ambunti Government Station) only
one person was attacked on his
private part. This person required
medical treatment and came from
Korogu village. A lady also claimed
to have been bitten by the Pacu on
her legs, just above her knees.
She had some scars present.
- No deaths from the introduced
Pacu Fish attacks were reported
from Korogu to Wagu villages.
Though native to South America, the pacu was introduced to New Guinea in the 1990's (ref. above).
Though this is not authoritative, there was an episode of River Monsters about pacu attacks on people. I believe this is relevant in that it includes interviews with locals who do claim that pacu can/do attack people in New Guinea (despite being herbivorous). So that at least provides an indication that at least one person is willing to "go on record" with the story that these fish do injure people. Whether these accounts are credible is a different question.