The production of farmed salmonids in Chile reached 550 000 t in 2004. The industry is considered to be consolidated, but with potential for further expansion to the south into pristine coastal areas. The environmental impacts of the salmonid farming industry in Chile were reviewed in 1996, and evidence at that time did not suggest significant adverse effects. However, after almost ten years of sustained growth, current evidence indicates that significant loss of benthic biodiversity and localized changes in the physico-chemical properties of sediments have occurred in areas with salmonid farms. Furthermore, the presence of these farms significantly increases in pulses the density of dinoflagellates. Data suggest that escaped farmed fish may have an impact on native species, although their survival in the wild appears low. The abundance of omnivorous diving and carrion-feeding marine birds increased from twofold to fivefold in areas with salmon farms compared with control areas without them. It is urgent that an ecosystem approach be implemented to assess all impacts of salmonid farming on coastal ecosystems in southern Chile.

Invasion by marine nonindigenous species (NIS) is a spread phenomenon. The tunicatePyura praeputialisshows pronounced disjoint geographical distribution: along thousands of kilometers in wave-swept headlands on the southeastern coast of Australia, from where it appears to have originated, and exclusively along 60–70 km inside the Bay of Antofagasta, Chile. mtDNA sequences suggested that the species invaded this rocky shore recently. We used field manipulations and juvenileP. praeputialistransplant techniques to test hypotheses regarding the capacity of the tunicate to survive and grow at different sites and tidal heights inside and outside Antofagasta, and its competitive performance for primary space (inside the Bay) against the native musselPerumytilus purpuratus. We conclude that survival and growth ofP. praeputialisshowed no significant differences among sites inside and outside the Bay, and suggest that the restrictive distribution of the species in Chile is caused by a specific oceanographic retention mechanism and/or its brief larval dispersal. We demonstrated that, inside the Bay,P. praeputialisoutcompetesPerumytilusfrom the Mid–Low intertidal, constrainingPerumytilusto the Upper Mid-Intertidal, modifying the local pattern of intertidal zonation. We show that predation onP. praeputialisjuveniles by starfish and snails constitutes a regulatory mechanism for the setting of its low intertidal limit. Major ecological impacts caused by NIS invasions to rocky shores by aggressive primary space users may result in negative aspects, but also may contribute to biodiversity enhancement. We call attention to the need for increment manipulations and testing of ecological hypotheses regarding marine NIS.

Biogeographical explanations for the extant and paleo disjoint geographical distribution in the southern hemisphere of five species of nearshore marine benthic invertebrates: Gaimardia trapesina, Ostrea chilensis, Pyura stolonifera taxonomic complex, Aulacomya ater and Concholepas concholepas, showing distinctive reproductive strategies and early life history characteristics are reviewed and analyzed. Through the use of published and new information we contrasted the following hypotheses: a) vicariance-historical process, b) epiplanktonic larval dispersal, c) juvenile/adult dispersal through rafting and d) planned or accidental anthropogenic dispersal mechanisms. The juvenile/adult transoceanic dispersal hypothesis by rafting was the only one impossible to be rejected for the species analyzed. The implication and future direction for research in this area are discussed