Look at that grin! That's the terrifying mouth of a pacu, an omnivorous South American freshwater fish that's a cousin to the infamous piranha. And like their relative, they're usually found only in the Amazon...so what was this one doing in the California Delta?

KCRA reports that Cathy Blanc was fishing in the delta when she reeled in two of these guys, and said "this looks like a piranha, sorta, something's not right!"

It turns out that she'd caught two pacu, "likely illegally dumped in this case," KCRA reports,"disrupting the ecosystem as a non-native species."

And disruptive they can be, as they can easily grow to 3 1/2 feet long and "may out-compete native species for available food, habitat, and other resources, or displace them by introducing exotic parasites or diseases," per Wikipedia.

They don't just look scary: a pacu's jaw is so strong, the Scotsman reports, they can "easily crush a walnut in its mouth." And while they're described by fish enthusiasts as "docile," they have been known to get aggro! For example, there's the case of a toddler who needed surgery after one gnawed on her finger, causing one expert to say "Pacus will eat anything, even children’s wiggling fingers...It’s just their natural behavior. The fish don’t know what they are eating until they take a bite."

In any case, delta area walnuts and toddlers have two fewer pacu to worry about today, as Blanc says that of the two she nabbed, one went to a bait shop for "further investigation," while the other was filleted but "has gone uneaten."