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 tunicate Pyura praeputialis shows 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 juvenile P. praeputialis transplant 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 mussel Perumytilus purpuratus. We conclude that survival and growth of P. praeputialis showed 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 and͞or its brief larval dispersal. We demonstrated that, inside the Bay, P. praeputialis outcompetes Perumytilus from the Mid-Low intertidal, constraining Perumytilus to the Upper MidIntertidal, modifying the local pattern of intertidal zonation. We show that predation on P. praeputialis juveniles 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.

Intertidal mussels usually form complex multilayered matrices with density-dependent effects on survival and growth, and self-thinning scaling between biomass (B) and density (N) is expected. This article develops a tridimensional model of space-driven self-thinning that in addition to B-N explicitly includes the degree of packing of the mussels, measured as the number of layers (L). The structure of our model (B-N-L) encompasses previous bidimensional models (B-N) of self-thinning as special cases and enables comparisons between mono- and multilayered populations. We contrast the predictions of the bi- and tridimensional models using data obtained from Perumytilus purpuratus mussel beds on the rocky shores of central Chile monitored during a 28-mo period. The tridimensional model suggests that density dependence is much more frequent than hitherto indicated by bidimensional models. We propose that our space-driven tridimensional model may be applied not only to mussels but also to other species where spatial overlapping configurations occur.

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Shell-shape variation in the Chilean blue mussel Mytilus chilensis was examined in eight populations covering the totality of its distribution range, which represents over 1800 km of latitudinal gradient in the southeastern Paci¢c. The shell outline shapes were assessed using elliptic Fourier analysis followed by canonical variates analysis. Fourier coe⁄cients showed a highly signi¢cant morphological variation between the populations studied. Canonical variates analysis showed a visual association of the First canonical with convexity of ventral edge and umbo shape, while the second axis was associated with shell elongation. Previously described genetic patterns were marginally congruent with our morphometric pattern, though geographic distance had a stronger e¡ect on morphology. Shape change (elongation) was correlated with latitudinal clinal variation. The morphometrical analysis proved to be an important tool for evaluating the components of shell-shape variation in mussels and to document association patterns with geographical and ecological variables. Such patterns are useful to establish awide ¢eld of work, including sexing, stock recognition, traceability studies and productive management in general.FONDECYT-Chile through project 1050848

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IntroducciónLas surgencias costeras derivadas del viento se observan a lo largo de muchas costas del mundo. Son fuertes y persistentes en las principales regiones de surgencia frente a costas de latitudes medias de los mayores continentes (e.g., el Sistema de Humboldt frente a las costas de Chile y Perú), y resulta en el enfriamiento y el enriquecimiento del medio ambiente marino, el cual se caracteriza por altos niveles de productividad y biomasa (Fonseca y Farías 1987, Barbieri et al. 1995.El fuerte transporte superficial y la mezcla profunda de plancton pueden influir negativamente en la productividad