Loayza E. auteur aut IRD Bertrand Arnaud auteur aut IRD Guillard J. auteur aut IRD La Cruz L. auteur aut IRD Lebourges Dhaussy Anne auteur aut IRD Vargas G. auteur aut IRD Lazzaro Xavier auteur aut IRD text journalArticle eng text/pdf reformatted digital access For the last two decades, a rapid eutrophication process impacts Lake Titicaca, the largest tropical freshwater lake in South America and the main highest Great Lake. This is especially notorious in the Bolivian sector of its shallow Lago Menor sub-basin. Lago Menor is deteriorated by the combination of multiple contaminations (domestic, industrial and mining) from untreated wastewater discharged from the urban area of El Alto, indiscriminate overfishing, and climate change. These threats particularly affect the native Andean killifish genus Orestias, the ecology and dynamics of which require in-depth studies with non-invasive techniques. Here, we use hydroacoustic method to evaluate fish patterns of distribution and abundance in the Lago Menor. Hydroacoustic data were collected during the 2015 rainy season (November) with vertical beaming at 120 kHz along transects that sum a total length of 140 km. Our results showed that the proxy of fish biomass was linked to Lago Menor bathymetry. Furthermore, the vertical fish biomass proxy was steady from 3 to 20 m. This pilot study provides the first image of fish, mostly Orestias spp., distribution and opens future studies to deepen knowledge on their ecology and ethology, and regular monitoring of their population and stock for the fisheries assessment in Lake Titicaca. specialized BOLIVIE 032TECHNO 034BIOVER01 4 2 034 [6 ] 2020 2576-5523 https://www.documentation.ird.fr/hor/fdi:010081736 10.24966/AAF-5523/100034 2576-5523 [F B010081736] https://www.documentation.ird.fr/hor/fdi:010081736 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2021-08/010081736.pdf IRD - Base Horizon / Pleins textes 2021-04-19 2025-02-24 fdi:010081736 fre