Galaxias platei is widespread and common in southern South America, but its ecology is poorly documented relative to other native species, especially those of commercial importance. Galaxias platei occurs across a large range of environmental conditions, including hydrologically isolated, high‐elevation lakes. Consequently, there were several lakes in the Patagonian region where it was the only native fish species. Introduction of salmonids into almost all lakes in Patagonia where G. platei occurs has potentially resulted in changes in its ecology and behaviour. Thompson Lake is a small, high‐elevation lake located in the Aysen River basin (Chile) where G. platei still occurs essentially in isolation. We collected G. platei from this lake to characterise the ecology of the species in the absence of other native and introduced fishes. We documented age and growth patterns from otolith analysis and characterised size‐ and age‐specific habitat use, diet and trophic niche. In Thompson Lake, G. platei is long‐lived and grows to comparatively large size (max. age = 18 years; max. TL = 348 mm). As it grows, it exhibits an ontogenetic niche shift in habitat use, diet and trophic niche. Large adults are piscivorous, and they occupy deep benthic habitats. Preservation of the last few remaining lakes where G. platei is found in isolation is an important priority for maintaining the full expression of ontogenetic niche variation in this species.

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We study the economic performance of Benthic Resource Management Areas (BRMAs) in central-southern Chile. The analysis considers 26 managed areas with Agreements of Use declaring Chilean abalone (Concholepas concholepas) to be the main exploited benthic resource from 2001 to 2003. Our analysis explores the role played by several characteristics thought to be potential BRMA performance determinants. These variables were defined and grouped into four types: economic, environmental–biological, institutional–organizational, and organizational leader. Our results indicate that the price of Chilean abalone, the size of the habitable area, the target resource density, the density of other resources, and leader experience are determinant factors for the economic performance of the BRMAs under study.

RESUMENGalaxias platei es la especie nativa de mayor distribución en la Patagonia Chilena, habitando ambientes fl uviales y principalmente lacustres. Utiliza variados hábitats, desde plataformas de arcilla consolidada a ambientes de sustrato fi no y otros con presencia de macrófi tas, vegetación leñosa o sustrato rocoso grueso. En este trabajo analizamos experimentalmente la selección de microhábitat de G. platei y su dependencia con la disponibilidad de refugio y la densidad de peces que lo utilizan. Para ello diseñamos experimentos con distintos niveles de refugio a diferentes densidades. Se recrearon microhábitats con refugio de canto rodado (sustrato grueso) y refugio de vegetación acuática, y microhábitats sin refugio de grava (sustrato fi no) y piedra plana simulando sustrato de arcilla consolidada. Las densidades probadas fueron 4, 8, 12 y 16 individuos. Encontramos que en todas las densidades, G. platei selecciona microhábitats con refugio y que al aumentar la densidad se produce un cambio en la preferencia desde microhábitats con vegetación hacia sustratos de canto rodado. Por el contrario, en todas las densidades probadas, los microhábitats sin refugio fueron rechazados signifi cativamente. Tanto la selección denso-dependiente de microhábitats, como la tendencia a un comportamiento gregario a mayor densidad de individuos, sugieren un comportamiento antidepredatorio de la especie. PALABRAS CLAVES:Experimentación, refugio, interacción intraespecífi ca, peces nativos, Patagonia. ABSTRACTGalaxias platei is the most broadly distributed fi sh specie in the Chilean Patagonia that inhabits in rivers and mainly in lakes systems. It occurs on varied habitats from clay platforms to thin substrates with presence of macrophytes, large woody debris and big boulders substrata. In this work we experimentally analyzed the microhabitat use of G. platei with dependence of refuge availability and fi sh density. We conduct experiments at different refuge levels for different fi sh densities. We build refuge microhabitat using boulders (thick substrate) and aquatic vegetation, and microhabitat without refuge using gravel (thin substrate) and slab stone to simulate a clay substrate. Fish densities tested were 4, 8, 12 and 16 individuals. G. platei select microhabitats with refuge at all densities tested, changing preference from vegetation to boulders at increasing density. Whereas, signifi cant selection against to all microhabitats without refuge at all densities. Density dependent use of microhabitat and the tendency to a gregarious behavior at high fi sh density, suggest an antidepredatory behavior of the specie.