Can anybody tell me what this is? It's eating my fish, and I don't know if it is a cottonmouth.

It's a snake. 

I would practice zero tolerance and kill it on sight.

Where do you live? What state?

Yes, that's a cotton mouth. My daughter is super into snakes and we have a snake ID book right here.

It says cotton mouths "have a dark mark from its eye to the edge of its jaw".  

The pictures aren't clear enough to make out if there is banding on it (book says "The cottonmouth has dark crossbands with lighter brown shading in the centre"), but that dark stripe from it's eye to it's jaw is a key ID , and that's clear as day. Call animal control or kill it.  Good luck!

Edit: My daughter begged me to add, please don't kill it.  Call animal control or a local reptile rescuer. :/  I love that kid but she's reptile crazy right now.  Do what you need to keep yourself and your family and pets safe.

Doesn't look poisonous. Water snakes here in Florida tend to only be poisonous if they're black in color.

Hmm, it also says adults patterns can darken so they appear to have no apparent bands. That looks like yours in the piture, just solid brown with the face markings.

Yeah the more I read, the more that really looks like a cottonmouth to me. It's also swimming in a distinct S shape, which is another identifier. This says they aren't as aggressive as many people think, prefering to retreat when they feel threatened, but since they are so dangerous when they do bite, I wouldn't take a chance. Be very safe!

I wouldn't jump to any conclusions. You can't see the scales clearly. The head, and any markings, are not super clear. There are at least a dozen colubrid that are uniformly brown in color, as this appears to be. Then again, there may be some markings that aren't obvious.

Take a look at the scales if you can from a safe distance. If they appear to have ridges in the middle, it could be a water moccasin. If it opens its mouth, and the inside is white, well, there you go.

It doesn't hurt to call animal control and have it identified, though. I just disagree that this is definitely a cotton mouth.

(August 6, 2018 at 12:52 pm)Minimalist Wrote: It's a snake. 

I would practice zero tolerance and kill it on sight.

It's a snake. Closest I'll get is 12 gauge range, and I'm afraid that wouldn't be good for my pond liner.

Northern Alabama is the location.

Could be four or five different species that all look similar. You'd have to get a clearer look at the scales and the head to know. If it makes you feel better, if it's an Earth snake, brown water snake or plain-bellied water snake, you're fine. The problem with patterns is that they can vary hugely within a single species. Take a peek in its mouth. That'll tell you for sure.

(August 6, 2018 at 12:49 pm)popeyespappy Wrote: Can anybody tell me what this is? It's eating my fish, and I don't know if it is a cottonmouth.

It might be a cotton mouth regardless don't try and remove it yourself better safe then bitten .