Dietary-morphological relationships in fish assemblages of small forested streams in the Bolivian Amazon

Abstract – We explored the relationships between diet and morphology in 30 fish species from forested tropical streams of the Bolivian Amazon. These species were first assigned to eight broad trophic guilds based on stomach con-tents analysis. The relationships between diet and morphology were then examined using Redundancy Analysis, after having checked for potential phylogenetical effects. Results show that, independently of any phylogenetic constraints, some of the trophic guilds could be grossly predicted from few relevant morphological attributes (i.e. relative intesti-nal length, standard length and mouth orientation) and thus suggest a significant link between diet and morphology. In other words, species having similar diet tend to converge to some extent on some morphological attributes. This link was nevertheless rather weak, suggesting that even if morphology may set limits to patterns of resource use, these limits are broad enough to allow fishes changing their choice of prey resources to respond to local biotic and/or abioti

Detecting natural hybridization between two vulnerable Andean pupfishes (Orestias agassizii and O. luteus) representative of the Altiplano endemic fisheries

The detection of hybridization among freshwater fish species is of main concern for conservation programs and fish farming. We assessed the incidence of natural hybridization between two vulnerable species of Andean pupfishes (Cyprinodontidae; Orestias agassizii and O. luteus) that represent an important component of local fisheries. We combined mitochondrial and nuclear DNA sequencing, microsatellites genotyping and morphometrics to characterize hybridization patterns between the two species in lakes Titicaca and Uru Uru (N = 175). The clustering analysis of 10 microsatellite loci together with heterozygosity distribution at seven species-specific diagnostic sites in rhodopsin (nuclear DNA) proved to be a robust diagnostic tool to detect F1 and potential backcross hybrids. For the first time on a genetic basis, we confirmed the incidence of natural hybridization between the two Andean pupfishes, at frequency rates reaching almost 10 %. The morphological intermediacy criterion (relative to parental species) did not apply in hybrids, since the latter (i) deviated through their larger caudal peduncle height, and (ii) had greater, overlapping ranges in their morphometric ratios. Although viable F1 and F2 hybrids between O. agassizii and O. luteus had been reported under controlled conditions, the ecological and/or demographic factors facilitating interspecific gene flow in the wild remain speculative. We recommend that regional fish farming and restocking programs targeting O. agassizii and O. luteus call on the genetic diagnosis of hybrids to avoid the potentially deleterious impacts of releasing hybrid populations in the wild

Mercury contamination level and speciation inventory in Lakes Titicaca and Uru-Uru (Bolivia) : current status and future trends

Aquatic ecosystems of the Bolivian Altiplano (similar to 3800 m a.s.l.) are characterized by extreme hydro-climatic constrains (e.g., high UV-radiations and low oxygen) and are under the pressure of increasing anthropogenic activities, unregulated mining, agricultural and urban development. We report here a complete inventory of mercury (Hg) levels and speciation in the water column, atmosphere, sediment and key sentinel organisms (i.e., plankton, fish and birds) of two endorheic Lakes of the same watershed differing with respect to their size, eutrophication and contamination levels. Total Hg (THg) and mono-methylmercury (MMHg) concentrations in filtered water and sediment of Lake Titicaca are in the lowest range of reported levels in other large lakes worldwide. Downstream, Hg levels are 3-10 times higher in the shallow eutrophic Lake Uru-Uru than in Lake Titicaca due to high Hg inputs from the surrounding mining region. High percentages of MMHg were found in the filtered and unfiltered water rising up from <1 to similar to 50% THg from the oligoihetero-trophic Lake Titicaca to the eutrophic Lake Uru-Uru. Such high % MMHg is explained by a high in situ MMHg production in relation to the sulfate rich substrate, the low oxygen levels of the water column, and the stabilization of MMHg due to abundant ligands present in these alkaline waters. Differences in MMHg concentrations in water and sediments compartments between Lake Titicaca and Uru-Uru were found to mirror the offset in MMHg levels that also exist in their respective food webs. This suggests that in situ MMHg baseline production is likely the main factor controlling MMHg levels in fish species consumed by the local population. Finally, the increase of anthropogenic pressure in Lake Titicaca may probably enhance eutrophication processes which favor MMHg production and thus accumulation in water and biota

Mercury contamination level and speciation inventory in Lakes Titicaca & Uru-Uru (Bolivia): Current status and future trends

International audienceAquatic ecosystems of the Bolivian Altiplano (∼3800 m a.s.l.) are characterized by extreme hydro-climatic constrains (e.g., high UV-radiations and low oxygen) and are under the pressure of increasing anthropogenic activities, unregulated mining, agricultural and urban development. We report here a complete inventory of mercury (Hg) levels and speciation in the water column, atmosphere, sediment and key sentinel organisms (i.e., plankton, fish and birds) of two endorheic Lakes of the same watershed differing with respect to their size, eutrophication and contamination levels. Total Hg (THg) and monomethylmercury (MMHg) concentrations in filtered water and sediment of Lake Titicaca are in the lowest range of reported levels in other large lakes worldwide. Downstream, Hg levels are 3-10 times higher in the shallow eutrophic Lake Uru-Uru than in Lake Titicaca due to high Hg inputs from the surrounding mining region. High percentages of MMHg were found in the filtered and unfiltered water rising up from <1 to ∼50% THg from the oligo/hetero-trophic Lake Titicaca to the eutrophic Lake Uru-Uru. Such high %MMHg is explained by a high in situ MMHg production in relation to the sulfate rich substrate, the low oxygen levels of the water column, and the stabilization of MMHg due to abundant ligands present in these alkaline waters. Differences in MMHg concentrations in water and sediments compartments between Lake Titicaca and Uru-Uru were found to mirror the offset in MMHg levels that also exist in their respective food webs. This suggests that in situ MMHg baseline production is likely the main factor controlling MMHg levels in fish species consumed by the local population. Finally, the increase of anthropogenic pressure in Lake Titicaca may probably enhance eutrophication processes which favor MMHg production and thus accumulation in water and biota