People: María del Carmen Diéguez, Julio Lancelotti, Miguel Pascual, Pablo Yorio.

The Strobel Lake Meseta in the Santa Cruz Province is spotted by hundreds of shallow lakes rich in aquatic biodiversity, including several endemism of aquatic invertebrates and vertebrates.Growing trout aquaculture prompts economic expectations, as well as concerns about ecological impacts. Our research aims at identifying keys to biological integrity and understanding the role that exotic trout play in these systems, to generate management recommendations for aquaculture practices and conservation of native biota.              

Whereas permanent water bodies are scarce in arid Patagonia, some areas of the central basaltic meseta are spotted by natural depressions that collect water from snow and ice melt, which represent an important water reservoir for this arid region. These macroecosystems, have a rich bird fauna including the hooded grebe, Podiceps gallardoi, an endemic species discovered in 1974, considered Near Threatened. A few lakes were planted with rainbow trout in the mid 1990´s, generating a growing aquaculture activity, as well as concerns about potential impacts on this unique ecosystem.

Fish introductions in fishless lakes have provided some of the best known examples of trophic cascades and regime shifts to be found in the ecological literature.

We initiated a long-term research project on shallow meseta lakes to identify the keys to biological integrity and to evaluate the role that exotic salmonids play in these systems. We focus our current research on one particular system, the Strobel Meseta (48º50`S, 71º20´W, 900 a.s.l, 2500km2), which holds over a thousand shallow lakes.

The initial activities of this project include inventory work and basic functioning assessment.     

Goals

Generate a classification and catalog of shallow meseta lakes based on field-based and remote-sensing variables.

Identify associations between habitat variables, community structure, aquatic bird fauna and the suitability for aquaculture, in order to generate precautionary principles for the geographic management of trout aquaculture.

Analyze the trophic and community structure in representative lakes and in lakes with contrasting production history.

Generate mechanistic hypotheses about the ecological role and the potential effects of rainbow trout in these lakes to guide future research.

Some specific activities

Characterize representative lakes based on limnological and community variables, including aquatic birds, and on their value for aquaculture as perceived by producers.

Characterize the trophic structure of communities in representative lakes based on stable isotope analysis.

Generate a geographic information system (GIS) to house and analyze all the geographic information collected for this project.

Apply habitat models to analyze the association of aquatic birds, key invertebrate species and physical, chemical and satellite-generated variables.

Classify lakes according to their value in terms of biodiversity and for aquaculture.

Explore correlations between field-generated data and spectral signatures of lakes in search of algorithms to extrapolate field-based assessments to all lakes in the meseta.

Evaluate alternative strategies for conservation-oriented management of aquaculture.

Results

We generated maps that rate individual lakes in the meseta as bird habitat and based on aquaculture potential. T the kind of information that managers could use to analyze precautionary management options. While the main targets of this advice are provincial wildlife and fisheries administrations, we work together with aquaculturists to understand their expectations, and to identify realistic measures of aquaculture regulation.        

Other activities are directed at generating more specific hypotheses about community structure, trophic relationships, and dynamic links between exotic trout and key species in lake communities. These hypotheses will guide the design of future research, which we visualize as addressing more mechanistic aspects of the dynamics of trout in lakes and their interaction with the native communities. We expect such research to go beyond just identifying critical habitat to understanding community impacts at the single lake level of alternative aquaculture practices (fish loads, harvesting schedules, and resting periods).