offers to sell

[Docter]

I try to sell fish but cannot set price Is this a bug or am I not understanding the way to do it

[phullfatt]

you may be asking for more than you have room to store is one reason

[Docter]

I am not trying to buy fish I am trying to sell fish

[Fexno]

look at this thread

(you might want to skip to the part where he explains how to put on your own trades ;)

[MuffinMule]

I am not trying to buy fish I am trying to sell fish

Yes, but you have to have room for whatever you are going to receive for the fish.
So, for instance, if you are selling them for 100 pine logs, then there must be space for 100 pine logs in your storage.