<p>In this paper, we investigate the dynamics of a delayed reaction–diffusion mussel–algae system incorporating a novel delay-dependent harvesting term. Compared to the non-harvesting scenario, the introduction of harvesting intensity induces multiple positive constant equilibria and gives rise to backward bifurcation phenomena. We firstly establish the global existence and boundedness of solutions for the non-delayed system, followed by a rigorous analysis of the necessary conditions for Hopf bifurcation and Turing instability. Notably, our results demonstrate an inverse relationship between harvesting intensity and the Turing instability region, with numerical simulations confirming the potential occurrence of Turing–Hopf bifurcation. By employing crossing curve methods and treating the dual delays as independent parameters, we systematically examine the stability of positive equilibrium and the emergence of Hopf bifurcation on the two-delay plane. Our analysis reveals that population dynamics exhibit periodic oscillations when two delays exceed critical threshold values, accompanied by destabilization of the positive constant equilibrium. Furthermore, we develop an explicit analytical framework, combining center manifold theory for partial functional differential equations with normal form reduction, to characterize the properties of bifurcating periodic solutions. Theoretical predictions are substantiated through some numerical simulations. Finally, we summarized the main results of the full text and presented the future research directions.</p>