Abstract The amphipod Corophium volutator has a patchy distribution which has been related to different factors (both physical and biological) at different sites. Experiments in the Wadden Sea, involving manipulation of the densities of the lugworm Arenicola marina and the bivalve Cerastoderma edule showed strong negative effects of these two species on the abundance of C. valutator. This result could explain the distribution pattern of C. valutator found in the Wadden Sea. The question was if this would also be the case in other geographical regions. Therefore, these experiments were repeated under different physical conditions in two shallow and almost non-tidal soft-bottom bays in Gullmarsfjorden on the Swedish west coast. Again, a significant negative density-dependent effect on Corophium was found. This effect was even stronger when A. marina and C. edule occurred together. A. marina and C. edule affected the numbers of the two sexes of C. valutator in a similar way. However, in the treatments with h...