Scallop aquaculture in Chile suffers from intense fouling on culture facilities by invasive species such as the ascidian Ciona intestinalis and the bryozoan Bugula neritina. We examined the grazing effect of the rock shrimp Rhynchocinetes typus on fouling species, which colonize scallop pearl nets. We placed different densities of shrimp (0, 2, 5 and 10 individuals) in pearl nets with juvenile scallops (mean shell height 4.9 cm) at Tongoy Bay in northern-central Chile. We sampled the nets after 4 months (January-May 2007) and recovered 35-50% of the shrimp from the different treatments. The nets with 10 initial shrimp had a lower cover of the bryozoan B. neritina and lower densities of the ascidians C intestinalis and Pyura chilensis, which resulted in a 50% decrease in biomass of fouling on nets. Low scallop mortality and slightly higher (yet not significant) growth in treatments with high shrimp densities suggest a positive interaction between the shrimp and scallops. The native rock shrimp is therefore considered a good candidate as a biological control of fouling communities and this could have a potential for polyculture. (C) 2009 Elsevier B.V. All rights reserved.