I went loking for a link to show you 'cherry peppers' and found this very interesting site! If you substitute jalapeno, as you said, you are making the pepper much too hot, so it will overpower the fish in that recipe. Here is the link:

http://missvickie.com/howto/spices/p...ppersdict.html

I've only ever bought cherry peppers pickled, in a jar, we grew up with them!