Project Study Area


 Jack Stanford - FLBS Director; F. Richard Hauer - FLBS Professor of Limnology; Sarah O'Neal - FLBS Graduate Student; Mr. Fernando de Las Carreras - CEO, Nervous Waters of Argentina (NWA); Mr. Alejandro Menendez, Estancia Maria Behety (EMB); The Fly Shop; Frontiers International Travel

  • Define the status of the brown trout population
  • Learn more about the effect of fishing on population structure and productivity within Patagonia / Tierra del Fuego river systems
  • Find what factors, other than angling, may limit trout productivity in different reaches of the river system


Project Summary:

The objective of this study is to determine population parameters and factors controlling productivity of sea trout (sea-run brown trout) in the Rio Grande of Tierra del Fuego, Argentina. We are using the catch and release fly fishing operation of NWA and EMB as a basis for a mark and recapture study of the brown trout population within various study reaches of the river in association with other ecological measures that encompass the freshwater life cycle.

The long-term goal is to use the scientific information as a basis for development of a strategy that will sustain high quality angling and the associated ecotourism income in the Rio Grande. With this first year of work as a foundation and by inclusion of the Rio Grande in SaRON, we hope in coming years to attract funding to involve scientists from Argentina in the work and to use the results to better inform salmon and trout management worldwide.


Fish Tag Finder

FLBS researchers, with the assistance of local researchers and fishing guides, tag thousands of fish per year in Tierra del Fuego river systems in order to better understand fish migration patterns and to identify fish habitat areas.

If you have found a fish tag, you can visit the FLBS Fish Tag Finder site.




The Rio Grande and other rivers in the Patagonia and Tierra del Fuego (P-TdF) regions of South America provide some of the best sport fly fishing in the world. While salmonids are not native to South American rivers, they are now well established and fly fishing ecotourism is an important regional industry. However, concerns exist that the fishing pressure may have begun to impair trout population structure and productivity in some of the rivers.

The situation may be likened to Alaska in the 1960s when sport fishing for large trout was developed but has since declined coherent with increasing fishing pressure. Owing to concern about sustainability of high quality fly angling in the Rio Grande River in Tierra del Fuego, Argentina, NWA and EMB asked the FLBS to prepare a proposal to obtain scientific information about the fishery and to make management recommendations. We want to know:

  • the status of the brown trout population
  • the effect of fishing on population structure and productivity
  • what factors, other than angling, may limit trout productivity in different reaches of the river system
Objectives and Rationale

Our main objective is to document the population structure of the brown trout of the Rio Grande and examine controls on productivity, particularly juvenile recruitment. It is critical to clearly understand these important elements of trout ecology in the Rio Grande in order to assure the sustainability of the fishery, and thus its tremendous economic value. This aspect is of course most important to NWA and EMB and others who depend on the health of the trout populations in the river. Many if not most trout and salmon fisheries worldwide have been impaired because the impact of fishing on population structure was not documented and the information integrated into an adaptive management framework river by river. The cooperators wish to avoid this on the Rio Grande by directly evaluating the angling influence on the brown trout population.

We also are interested in documenting why brown trout and sea-run salmonid fishes have so successfully adapted in the Rio Grande. Specifically, we are interested in potential interactions between resident and sea-run life history types of brown and other salmonids that are present in the Rio Grande (e.g. Rainbow Trout), especially in relation to interbreeding and competition for food and space by juveniles. We believe that such information also is essential to sustaining high quality fishing in P-TdF, as well as better informing the science of salmon rivers worldwide.


NWA deploys a large number of guided fly fishers each year from Kau Tapen Lodge, Toonken Lodge, and Villa Maria Lodge and EMB from Maria Behety Lodge on the Rio Grande. Large numbers of fish are landed throughout the fishing season. Guides collect a specific suite of rapid assessment data on every fish landed by anglers as well as either tag or note recaptures of previously tagged fish, noting the location of every capture. This amounts to a large scale and spatially explicit mark and recapture study that will allow a robust estimation of population size.

Data collection by guides and anglers is coordinated by a FLBS graduate research assistant per protocols established herein. The FLBS graduate research assistant also collects an extensive suite of habitat and food web metrics for migratory, resident, and juvenile fish, again in spatially explicit format following the Protocol of the Salmonid Rivers Observatory Network (SaRON) of FLBS. All data will be communicated to and accessed from the SaRON data management system at FLBS. This data system is web based and will allow easy access to all information by the cooperators and other interested parties per agreement of the cooperators.