Juana Aigo

Distribution of introduced and native fish in Patagonia (Argentina): patterns and changes in fish assemblages

The interaction between native fishes and salmonids introduced in Patagonia at the beginning of the 20th Century, developed at the same time as the environmental change. The phenomenon of global warming has led to the formulation of predictions in relation to changes in the distribution of species, in the latitudinal dimension, both at intralacustrine, or small streams levels. The aim of the present work includes three main objectives: a) to compose a general and updated picture of the latitudinal distribution range of native and alien fishes, b) to analyze the historical changes in the relative abundance of Percichthys trucha, Odontesthes sp., and salmonids in lakes and reservoirs, and c) to relate the diversity and relative abundance of native and salmonid fishes to the environmental variables of lakes and reservoirs. We analysed previous records and an ensemble of data about new locations along the northern border of the Patagonian Province. We compared current data about the relative abundance of native fishes and salmonids in lakes and reservoirs, with previous databases (1984–1987). All samplings considered were performed during spring-summer surveys and include relative abundance, as proportions of salmonids, P. trucha, and Odontesthes sp. For the first time, we found changes in fish assemblages from twenty years back up to the present: a significant decline in the relative abundances of salmonids and an increase of P. trucha. We studied the association between the diversity and relative abundance of native and salmonid fishes and the environmental variables of lakes and reservoirs using Canonical Correspondence Analysis. Relative abundance showed mainly geographical cues and the diversity relied largely on morphometric characteristics. Relative abundance and diversity seem to have a common point in the lake area, included into the PAR concept. Native abundance and alien diversity were negatively related with latitude. Greater native diversity was observed in lakes with high PAR compared with salmonids. Historical changes such as southward dispersion, relative abundance changes, and geographical patterns for relative abundance and diversity are basic concepts needed not only in future research but also in management design for Patagonian fish populations.

Susceptibility of native perca (Percichthys trucha) and exotic rainbow trout (Oncorhynchus mykiss) to high temperature in Patagonia: different physiological traits and distinctive responses

The aim of this work was to explore for the existence of a physiological basis for the apparent exclusion of salmonid fish from the littoral zone of lakes in Patagonia in response to increasing water temperature, to the benefit of the native perca (Percichthys trucha). We conducted experiments on the thermal preferences of juvenile perca and rainbow trout collected in three sites of Northern Patagonia. We characterized the relationship between preferred and acclimation temperature (PT, AT) for perca and trout and analyzed between-sites variations in PTs. Both species responded with increasing PT to higher AT, but with differences in overall PT for perca from different sites (lower PTs for fish from cooler lake). In general, rainbow trout displayed lower PT and a narrower range of PT than perca. Our results provide the first comparative view of PTs of one important native fish and the main sport fish species of Patagonia. Native perca may be better equipped to cope with warmer waters than exotic rainbow trout, in agreement with their geographic distribution. Also, perca may have an advantage at the local level, particularly in littoral areas of lakes, through the alleviation of predation by and trophic competition with trout.

Traditional Mapuche ecological knowledge in Patagonia, Argentina: fishes and other living beings inhabiting continental waters, as a reflection of processes of change

BackgroundUnderstanding how people interpret environmental change and develop practices in response to such change is essential to comprehend human resource use. In the cosmology of the American indigenous peoples, as among the Mapuche people, freshwater systems are considered a living entity, where animals have an enormous role to play in the universe of meaning. However, human adaptive responses to freshwater system dynamics are scarcely examined. In this work a survey is carried out in three Mapuche communities of Argentine Patagonia to assess their traditional knowledge of the fishes and other non-human living beings that inhabit lakes and rivers. Both material and symbolic aspects are included, as are the differences in knowledge and use of the fishes between past and present times.MethodsOur methods were based on a quali-quantitative fieldwork approach. In-depth interviews were carried out with 36 individuals from three rural Mapuche populations in Neuquén province (Patagonia, Argentina). Free listing was used for inquiring about fish knowledge and use. Fishes were identified scientifically and ethnotaxonomically. In-depth analysis of the discourses was conducted, documenting the recognition, perception, and cultural significance of fluvial environments and their inhabitants. Quantitative survey results were analyzed with categorical statistical methods.ResultsThe body of knowledge of the communities studied reflects the socio-environmental changes experienced by Patagonian freshwater bodies. According to local perception, non-human beings live in these water bodies, guarding the environment, and they should not be disturbed. At present, five different fish species are identified, three of which are exotic, having been introduced at the beginning of the 20th century by the white man. These exotic trout (Oncorhynchus mykiss and Salvelinus fontinalis) are considered ill omens, indicators of the white man’s presence, and therefore their appearance presages negative events for the families. In addition, we found that Mapuche people differentiate fish species mainly by morphological, organoleptic and ecological attributes. Current consumption of fish by Mapuche communities is sporadic, in accordance with bibliography and ancient tales. Several fishing tools are used, including modern elements.ConclusionsOur data enable us to characterise dynamic traditional knowledge in these communities, which is flexible in nature and adaptable to new situations, demonstrated by the incorporation not only of new species but also new fishing tools. It also seems that new significances become absorbed in synchrony with the advance or arrival of exotic and invasive species. For the Mapuche, the presence of the white man heralded by exotic trouts speaks of how a recent event, such as the introduction of the salmonids, is already incorporated into Mapuche symbolism. Mapuche traditional knowledge and cosmovision on the use of fish and waters, a vision which promotes respect and the avoidance of actions that could disturb the beings (animals and sacred or mythological characters) that inhabit and take care of them should be fostered as part of management plans of regional natural resources. This paper contributes to the broader literature on freshwater resource management by providing empirical evidence of the critical role of local perceptions in promoting the sustainable management of natural resources.