A relative of the piranha, the pacu, was found in Swedish waters near Oresund Sound last week. It was about ten inches long, but this type of fish can grow to about four times that length. Why a South American fish would be in Swedish waters is not clear, but it could have been placed there by a home aquarium enthusiast. The problem is that they have been known to attack the male genitalia in places like Papau New Guinea and in South American waters.
While this all sounds very menacing, it may actually be that the pacu mistakes the male anatomy for tree nuts, which is a common food for them because they are vegetarian. Nuts that fall from trees into rivers and streams are crushed by their large strong teeth and powerful jaws for food. Any male fisherman or swimmers without trunks could be targeted for bites from the pacu. Some reports say some males swimmers have bled to death after the bites.
One fish in a very large body of water is not a problem, but no one knows if there might be a few more. Of course, the odds of anything happening are next to zero, but the situation serves more as an illustration of the effects of pet owners releasing exotic animals into the wild. Sometimes they are dangerous to people, but more often they are very destructive to local habitats.
Pythons in Florida, for example, may be killing tens of thousands of local, native animals and wreaking havoc ecologically. Asian carp in Midwestern American rivers have done much damage and might be able to get into Lake Michigan where they would undoubtedly cause much more damage.
So, this testicle-biting fish story is really about the much larger implications of pet owners releasing exotic species into environments where they don’t belong and causing far greater damage, than a very unlikely genital attack on an unsuspecting swimmer. Of course, the ‘fish bites nuts’ story will get much more attention in the international media.