Mussels and barnacles considered to be in competition with each other on the rocky shore because they both occupy space on rocks and can prevent each other from settling.
Step-by-step explanation:
Barnacles and mussels compete with each other for space and the competition with space is one of the strongest competitions especially when non-moving organisms are involved. Both the organism attach themselves on rocks and and then filter food from the surrounding waters.
The competition for space intensifies with increase in population density and in this case,it often leads to the elimination of either barnacles or mussels from the living space.