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Eutrophication is a key human-induced stressor in streams and often a consequence of intensified land use. We characterised how population density influences dissolved nutrients and its ratio in Pa...

Fluvial dynamics are driven by multiple environmental factors and scales. Studies coupling hydrological and nutrient dynamics of mountain streams are almost non-existent in the Northern Patagonian ...

Ecological communities are structured by combinations of factors known as habitat templates. These templates work as a filter allowing only species with particular traits or phenotypes to establish and persist excluding all others. Defining which habitat variables and spatial scales drive the assembly of freshwater communities is key to effective and efficient management of fluvial ecosystems. We took advantage of the relatively recent and well-studied history of salmonid introductions in Patagonia to evaluate if non-native species show different patterns of association with abiotic factors depending on the spatial scale of the environmental filter. We used a hierarchical approach to characterized environmental variables at the basin and reach scales to assess their influence on the presence, abundance and structure of the salmonid assemblages in breeding streams. We saw no evidence that presence/absence patterns of salmonid distribution were driven by landscape variables, except for those basins with physical environmental barriers to colonization. However, we did find evidence for relative abundances being influenced by climatic and geomorphological variables (e.g., precipitation and relief). Our results do not support a scenario in which any of the salmonid species modulates the distribution of the other species, suggesting that interference has played only a minor role in determining current fish distribution in fluvial systems of the region. Instead, current patterns of presence and abundance of salmonids are best explained as the product of environmental filters. Our findings contribute to our understanding of the ecology of individual species and provide insight into the mechanisms structuring fish assemblages in Southern Hemisphere’s lotic systems.

We characterized how land use influenced dissolved nutrients and periphytic algal biomass in an Andean basin from Northwest Patagonia. Nutrient export, especially dissolved inorganic nitrogen increased with human population density. However, no correlation between nutrient concentration and algal biomass was found, which could instead be limited by light availability. Our results suggest that local N-limited ecosystems are liable to eutrophication by increased demographic pressure and that alternative wastewater treatment strategies are necessary for sustainable growth.

Understanding how ecosystem processes influencing fish distribution operate across spatial scales is important to understand biological invasions. Salmonids, originally from the Northern Hemisphere, have been repeatedly introduced throughout the world, making them an ideal group to test hypotheses about factors driving invasions. We assessed the influence of environmental variables at the watershed scale on the abundance and structure of salmonid assemblages in the breeding streams of the Upper Limay river basin, Rio Negro, Argentina. We combined field captures with digital map data and geographic information systems to examine landscape-level patterns of salmonid abundance in 35 representative sub-basins of the environmental gradient. We employed a hierarchical cluster analysis and classification and regression tree models to relate the abundance of salmonids and types of species assemblages with environmental characteristics at watershed level. We found stream localization, precipitation regime, altitude and air temperature to be important predictors of the abundance and assemblage structure of salmonids. Total catches showed an increasing gradient of catch-per-unit-effort from west to east and from north to south, with Oncorhynchus mykiss being the most abundant species. O. mykiss relative abundance was westward skewed, where smaller catchments with steeper and shaded valleys are drained by less productive streams with more irregular hydrological regimes, like those found in this species' North American native range. In contrast, the abundance of Salmo trutta abundance was eastward skewed, where larger, sunnier and more gently sloped catchments result in more productive streams with stable hydrological regimes, like those found in that species' European native range. Thus, differential salmonid abundance could result from the interplay between the evolutionary fingerprint left by each species' native environment (especially flow and temperature regimes) and the availability of those conditions in new environments to which they have been translocated. By furthering our understanding of how landscape conditioned invasion success, these findings can help guide the management of economically important introduced fish.

According to assemblage theory, three factors regulate fish biogeography: restriction of dispersion, environmental restrictions and biotic interactions. The first two factors act on a regional scale and delimit the area of action of the third, which operates on a local scale. Salmonid introductions began in Patagonia in 1904, and this has led to a restructuring of trophic webs and an increase in the number of top predators. This situation allowed us to evaluate, in a natural setting, how communities are formed on different geographic scales. We studied two large basins in Patagonia, situated close to each other but with different assemblages of top predatory fish. We hypothesized that differences in the structuring of the top predator assemblages between and within the basins are due to 1) environmental factors and dispersion processes facilitated by connectivity on a regional scale; and 2) biotic interaction (internal dynamics) between native perch and salmonids, the former acting as a modulator of the top predator assemblages on a local scale. To test these hypotheses, we analysed the top predator assemblages of 16 lakes and one reservoir, as well as their environmental characteristics. We performed a cluster analysis and related the resulting assembly groups to environmental factors by means of a tree model. We also analysed fish diets, using a similarities test to study biotic interactions. On regional and local scales, water basin, degree of connectivity, area, temperature and Zoogeographic integrity coefficient (ZIC) were important factors in the structuring of top predator assemblages. On a local scale, creole perch modulates the salmonid populations through feeding and the consequent distribution of resources. Our work showed that the structure of top predator assemblages was determined by a combination of local and regional factors acting in synergy, as postulated by the assemblage theory. Fil: Fernández, María Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Lallement, Mailén Elizabeth. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Rechencq, Magali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Vigliano, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Sosnovsky, Alejandro. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Macchi, Patricio Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina

Salmonid sport fishery management in Argentinian Patagonia is usually guided by stakeholder perceptions, which do not consider the biological and ecological constraints acting upon aquatic resources. An example of this are management policies for Traful Lake, where Atlantic salmon, Salmo salar L., was actively stocked during the last decade in an attempt to change the fish assemblage structure and to create a highly valuable sport fishery. This study assesses the likelihood of these policies achieving such assemblage structure changes through the study of affluent-stream suitability as spawning and breeding grounds, lake fish assemblage parameters, trophic diversity and possible competition due to diet overlap. This study also assesses alternative management practices through population simulations and bioenergetic modelling under diverse catch-size limit scenarios. This study concludes that it is not advisable to try to generate a unique and distinctive sport fishery by stocking Atlantic salmon in an already renowned fishery in Northern Patagonia. Instead, a more comprehensive framework for decision-making is suggested, involving short-term studies that go beyond the specific problem of the target species and incorporate the whole fish assemblage using diverse approaches and modelling strategies. Fil: Rechencq, Magali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Vigliano, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Lippolt, Gustavo Enrique. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Alonso, Marcelo Fabián. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Macchi, Patricio Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Alvear, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Hougham, Virginia Noemí. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Denegri, Maria Amalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Blasetti, Guillermo. Autoridad Interjurisdiccional de las Cuencas de los ríos Limay, Neuquén y Negro; Argentina Fil: Juncos, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (CAB); Argentina Fil: Fernandez, Valeria. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Lallement, Mailén Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Juárez, Santiago Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina

The Chilean north Patagonian inland waters are characterized by their low mineral concentrations. In their original status, many of these ecosystems have native vegetation in their surrounding drainage basins, but in the last decades the native vegetation was replaced by agricultural, urban, and industrial zones, with as a result of these human alterations that those aquatic communities changed. The aim of the present study was to make a literature review about the ecological role of crustaceans in Chilean north Patagonian lakes and rivers. The literature mentioned the presence of amphipods (Hyalella), crayfishes (Samastacus spinifrons), and freshwater crabs (genus Aegla), and many of these species hold a conservation risk due to the consequences of habitat damage and/or their high endemism. These crustaceans are important for the degradation of particulate organic matter originating from the surrounding vegetation, and are prey for native and introduced salmonid fishes. Similar patterns had already been observed for Argentinean Patagonian rivers.

Habitat use in relation to the thermal habitat availability and food source as a forcing factor on habitat selection and use of Percichthys trucha (Creole perch), Oncorhynchus mykiss (rainbow trout), Salmo trutta (brown trout) and Salvelinus fontinalis (brook trout) were determined as well as future potential thermal habitat availability for these species under climate change scenarios Representative Concentration Pathways 4.5 and 8.5. This study was conducted in three interconnected lakes of Northern Patagonia (Moreno Lake system). Data on fish abundance was obtained through gill netting and hydroacoustics, and thermal profiles and fish thermal habitat suitability index curves were used to identify current species-specific thermal habitat use. Surface air temperatures from the (NEX GDDP) database for RCP scenarios 4.5 and 8.5 were used to model monthly average temperatures of the water column up to the year 2099 for all three lakes, and to determine potential future habitat availability. In addition, data on fish diet were used to determine whether food could act as a forcing factor in current habitat selection. The four species examined do not use all the thermally suitable habitats currently available to them in the three lakes, and higher fish densities are not necessarily constrained to their “fundamental thermal niches” sensu Magnuson et al. (1979), as extensive use is made of less suitable habitats. This is apparently brought about by food availability acting as a major forcing factor in habitat selection and use. Uncertainties related to the multidimensionality inherent to habitat selection and climate change imply that fish resource management in Patagonia will not be feasible through traditional incremental policies and strategic adjustments based on short-term predictions, but will have to become highly opportunistic and adaptive. Fil: Vigliano, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Rechencq, Magali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Fernández, María Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Lippolt, Gustavo E.. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Macchi, Patricio Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Events such as volcanic eruptions may act as disturbance agents modifying the landscape spatial diversity and increasing environmental instability. On June 4, 2011 the Puyehue-Cordon Caulle volcanic complex located on Chile (2236 m.a.s.l., 40° 02' 24? S- 70° 14' 26? W) experience a rift zone eruption ejecting during the first day 950 million metric tons into the atmosphere. Due to the westerly winds predominance, ash fell differentially upon 24 million ha of Patagonia Argentinean, been thicker deposits accumulated towards the West. In order to analyze changes on stream fish assemblages we studied seven streams 8, 19 and 30 months after the eruption along the ash deposition gradient, and compare those data to pre eruption ones. Habitat features and structure of the benthic macroinvertebrate food base of fish was studied. After the eruption, substantial environmental changes were observed in association with the large amount of ash fallout. In western sites, habitat loss due to ash accumulation, changes in the riparian zone and morphology of the main channels were observed. Turbidity was the water quality variable which reflected the most changes throughout time, with NTU values decreasing sharply from West to East sites. In west sites, increased Chironomid densities were recorded 8 months after the initial eruption aswell as lowEPT index values. These relationships were reversed in the less affected streams farther away from the volcano. Fish assemblages were greatly influenced both by habitat and macroinvertebrate changes. The eruption brought about an initial sharp decline in fish densities and the almost total loss of young of the year in themostwestern streams affecting recruitment. This effect diminished rapidly with distance fromthe emission center. Thirty months after the eruption, environmental changes are still occurring as a consequence of basin wide ash remobilization and transport. Fil: Lallement, Mailén Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Macchi, Patricio Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Vigliano, Pablo Horacio. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Juárez, Santiago Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Rechencq, Magali. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentina Fil: Baker, Matthew. University of Maryland Baltimore County; Estados Unidos Fil: Bouwes, Nicolaas. Eco Logical Research; Estados Unidos Fil: Crowl, Todd. State University of Utah; Estados Unidos

Andean Patagonian lakes are ultraoligotrophic, highly transparent water bodies with very low densities of organisms at the different levels of their trophic food webs. Little is known about spatial distribution and habitat use by fish in these lakes. Hydroacoustic and active sampling techniques were used to study the distribution, composition, and displacement of organisms in an Andean lake throughout the diel cycle on two different moon phase days. Sound scattering layers (SSLs) were found both in the near-shore and pelagic habitats at different times of the day. These SSLs, formed by galaxiid larvae and adults, underwent displacement during the time periods of dawn and dusk, giving rise to the redistribution of organisms in the different habitats. The organisms show high sensitivity to light intensity, displaying different behaviors depending on moon phases. Extensive diel vertical migrations show that the deep pelagic habitats provide diurnal refuge for native galaxiids in Andean Patagonian lakes. Due to the high densities of galaxiid larvae and adults, it is likely that diel migrations generate an active flow of energy and matter between habitats, which could have a profound influence on whole lake dynamics.

Exotic rainbow trout Oncorhynchus mykiss support an economically valuable recreational fishery in Patagonia but also create concern for impacts on native organisms. These concerns are intensified by the possibility of hatchery release programs in this region. We estimated losses of different prey from predation by rainbow trout in Lake Moreno, Río Negro Province, Argentina, using a bioenergetics model combined with input data from directed sampling on growth, seasonal diet, distribution, and thermal experience. The fish community was sampled seasonally using gill nets, hydroacoustics, and ichthyoplankton nets. Pelagic galaxiid larvae and benthic juvenile and adult small puyen Galaxias maculatus were the most important components of the diet. Bioenergetics simulations showed that over a 6-year life span in the lake (ages 1-7), rainbow trout attained a body mass of 2.3 kg and consumed 74.7 kg of food, of which 20% consisted of galaxiid larvae and 16% consisted of adult small puyen. Based on an estimated abundance of 29,000 rainbow trout of ages 1-7, this predator exerted significant but sustainable mortality on the native prey populations, consuming 44 metric tons or an estimated 23% of the annual larval galaxiid production and 35 metric tons of adult small puyen, which represented an unknown fraction of the postlarval population. Galaxiids supported the estimated predation demand under current conditions. However, simulations of stocking strategies normally proposed for this region showed that consumption demands on prey would increase to unsustainable levels, reducing native fish populations and likely reducing growth of rainbow trout. It is also probable that the fish community composition would shift further in response to the increased demand for prey by stocked predators. This implies that in some cases, stocking could jeopardize sport fisheries; stocking strategies should be evaluated on a case-by-case basis to be consistent with specific objectives for native fish conservation and sustainable food web interactions. Fil: Vigliano, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Beauchamp, David. University of Washington; Estados Unidos Fil: Milano, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Macchi, Patricio Jorge. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Alonso, Marcelo Fabián. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Garcia Asorey, Martin Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Denegri, Maria Amalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Ciancio Blanc, Javier Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Lippolt, Gustavo. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Rechencq, Magali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Barriga, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Andean Patagonian lakes are ultraoligotrophic and deep, have simple food webs and low fish diversity and abundance. In this work the distributional abundance data of fish was studied in two interconnected Andean Patagonian lakes with varying proportions of contrasting habitat types. Hydroacoustic data (120 kHz) were used to analyze fish abundance and habitat use during the mixis and stratification periods. Three types of habitat (near shore, surface pelagic and deep pelagic) and two groups of fish, based on size (Big Fish >12 cm total length and Fish Larvae and Small Fish