Fish name: Bullhead catfish
US location: Anywhere in the continental US exception Washington and Oregon. More common on the east half, but has been introduced on the west coast as well.
Why they're dangerous?: The dorsal fin and side fin spikes can leave a nasty sting.
Should I be concerned?: If you're catching them, you should be aware of the sting that can be inflicted. Even the most experienced catfisherman have been stung, and more often than not you'll get stuck. Bullhead catfish don't seem to carry poison in their spines, but the puncture and skin irritation can cause swelling, soreness, and pain for a few days.
Remedies: Vinegar or urine on the wound can help. Rubbing the cat's belly on the wound has also been suggestion, but I'm not sure about that one. It's best to just clean the wound and monitor it for signs of infection.