Why does my dog smell like fish after being outside?

My dachshund smells like fish every time she goes outside. Whether she's outside for five minutes or an hour she smells really fishy. I know she's not rolling in anything because I usually go out with her and she just goes to the bathroom. Does anybody know what causes her to smell like this? :(

Actually this happened to me a few years back. So I decided to tail my dog while he was out wandering the 'hood, and I discovered some people had come up to him and rubbed fish on him for fun. I beat the sh't out of them and went to jail. Would not recommend it.

It may be her anal glands. I knows it sounds gross, but when dogs have compact anal sacs they smell a bit fowl and fishy. Perhaps take her to a groomer or vet to get them to express the glands. It can be done at home, but I would trust a professional to do this.