Obviously they want a women that will enjoy fishing.
Same reason anyone else shares their hobby?
Because the waters quench and nourish. They will make every union flourish. So proudly do I display my fish ready to serve my mate a tasty dish.
A dating profile is a good place to advertise interests.
Fishing is my favorite thing in the world. I would take a bad day of fishing over a good day of every other hobby I have. Plus it feeds me and my friends/family.