Motivated by the work of Greenberg-Vatsal and Emerton-Pollack-Weston, I investigate the extent to which Mazur's conjecture on the growth of Selmer ranks in Zₚ-extensions of an imaginary quadratic field persists under p-congruences between Galois representations. As a first step, I establish Mazur's conjecture for certain triples (E, K, p) under explicit hypotheses. Building on this, I prove analogous results for Greenberg Selmer groups attached to modular forms that are congruent mod p to E, including all specializations arising from Hida families of fixed tame level. In particular, I show that the Mordell-Weil ranks in non-anticyclotomic Zₚ-extensions of K remain bounded for elliptic curves E' such that Ep and E'p are isomorphic as Galois modules.
Anwesh Ray (Mon,) studied this question.