We prove that the dual fine Selmer group of an abelian variety over the unramified Z-extension of a function field is finitely generated over Z. This is a function field version of a conjecture of Coates--Sujatha. We further prove that the fine Selmer group is finite (respectively zero) if the separable p-primary torsion of the abelian variety is finite (respectively zero).
Ghosh et al. (Tue,) studied this question.