The study related the density of herbivores to the length and density of Prionitis spp. in Oregon’s coastal tidepools. Oregon’s coastal rocky intertidal tidepools contain a variety of species interactions, including algal grazing by herbivores. The red branched algae Prionitis spp. is found throughout the rocky intertidal in the low and high zones. In the intertidal, Prionitis spp. has many herbivores that graze on it; chitons, limpets, sea urchins, and snails being the most common in tidepools. An observational study was conducted throughout the rocky intertidal and the data was analyzed using excel. Herbivore density was significantly different between the high and low zone tidepools, while Prionitis spp. size and density were similar. The density of herbivores described a little bit of the variation in Prionitis spp. size and so did Prionitis spp. density for herbivore density. Herbivores do not strongly influence the size and density of Prionitis spp. in rocky intertidal tidepools.