Seasonal and depth variations in diet composition and dietary overlap between three native 1 killifish of an emblematic tropical-mountain lake: Lake Titicaca (Bolivia) 2 3 Erick Loayza 4 5 6 ABSTRACT 25Lake Titicaca (~3800 m a.s.l.), an emblematic tropical-mountain ecosystem is the 26 major source of fish for people on the Altiplano. The Andean killifish genus Orestias, 27 represent an important resource for local fisheries in Lake Titicaca. It has been suggested 28 that exist an effect of segregation in the Lake Titicaca in order to avoid competition for 29 food resource between native fish species, due most of Orestias species share the littoral 30 habitat, which is now also share with introduced species. Such scenario increases the 31 pressure for food resource. Here I examined the gut content of O. luteus, O. agassizii and 32 O. mulleri (Cuvier & Valenciennes, 1846) from a bay of Lake Titicaca during rainy (April) 33 and dry season (July) with the predominance method, frequency of occurrence and 34 numerical percentage to describe the diet and dietary overlap between these native fish. I 35 also applied a PERMANOVA test in order to determine diet variations related to depth and 36 seasonally, as well as the Levins and Pianka's index to test diet breadth and dietary overlap 37 respectively. 396 gut contents were evaluated, identifying a high frequency of amphipods 38 and molluscs in the three Orestias native species. Diet breadth revelled a selectivity for a 39 few preys and the composition of the diets was influenced mainly by depth, followed by 40 seasonality (PERMANOVA, P = <0.05). Dietary overlapping between O. luteus and O. 41 agassizii was evidenced in the rainy season. During the dry season, the three species 42 undergone dietary overlapping. This study provided a detail knowledge on the diet 43 variations of native species in Lake Titicaca, especially for Orestias mulleri, a little-known 44 species. Here I also discussed the importance of the amphipods as a food resource in Lake 45 Titicaca not only for fish community, but for the food web in general. The seasonal and 46 depth diet variations here discussed are relevant for fisheries management and conservation 47 and could be used to guide aquaculture development in Lake Titicaca. 48 3 49
Microplastic pollution is a widespread environmental concern. Like other anthropogenic pollutants, microplastics can reach aquatic ecosystems through rivers and interact with the aquatic biota. For instance, Lake Titicaca (between Bolivia and Peru), one of the great ancient lakes in South America (3,809 m a.s.l.), shows a pollution problem, particularly in the southern shallow basin (Lago Menor) in Bolivia. Nevertheless, our knowledge of the presence of microplastics and their interaction with the biota of Lake Titicaca is limited. Therefore, this study evaluated the presence of microplastics in the stomach content of the four fish species targeted by local fisheries in Lago Menor of Lake Titicaca (Orestias luteus, Orestias agassizii, Trichomycterus dispar, and Odonthestes bonariensis; N = 1,283), and looked for relationships with trophic guilds or fishing areas. Additionally, surface water was analyzed to evaluate the presence of microplastics in the water. The evaluation of microplastics was carried out by visual observations. We observed that the frequency of microplastic ingestion was low in all species (<5%). Conversely, microplastic was present in the water, with the highest quantity at the southern part of Lago Menor (103 ± 20 particles per L), without differences in the microplastic number between sites. Most microplastics counted in stomach contents were fibers, whereas water samples mainly contained fragments. Our results point to microplastic pollution in Lago Menor of Lake Titicaca. However, we could not determine the pollution rate due to considerable methodological limitations. Further research will be needed to robustly detect microplastics in Lake Titicaca and their impact on the fish species in the lake.
The Metropolitan Region of La Paz (MRDLP) in Bolivia has grown with minimal planning, leading to major changes to the natural habitat. Currently, citizen science is becoming an important contributor of information on the biodiversity of urban areas. This study presents novel records of native Andean killifish (Orestias spp.) in the MRDLP obtained from the iNaturalist website, expanding its distribution and highlighting the important role of citizen participation as a tool to expand biodiversity knowledge and monitoring of ecosystems sensitive to climate change.
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