The decline and collapse of populations have been reported for a large range of taxa. Diadromous fishes migrate between fresh water and the sea and encounter many anthropogenic pressures during their ...complex life cycle. In spite of being of ecological, cultural and economic interest, diadromous fishes have been in decline for decades in many parts across the world. In this study, we investigated the change in five diadromous fish counts in France over a 30-year period using 43 monitoring stations located in 29 rivers across 18 catchments. Our hypothesis was that the counts of these species evolved in a contrasting way between catchments. We also tested the effect of five drivers potentially contributing to the observed trends: catchment, latitude, presence of commercial fisheries, improvement of ecological continuity and salmon stocking. We found contrasting trends in fish counts between species at the national scale, with some taxa increasing ( Anguilla anguilla and Salmo trutta ), some showing a slight increase ( Salmo salar ) and some decreasing ( Alosa spp. and Petromyzon marinus ). For each taxon, except Anguilla anguilla , we highlighted a significant catchment effect indicating contrasting trends between catchments and stations. However, we found no significant effect of catchment characteristics for any of the studied taxa.
Le déclin et l'effondrement des populations ont été signalés pour un large éventail de taxons. Les poissons amphihalins migrent entre les eaux douces et la mer, et subissent de nombreuses pressions anthropiques au cours de leur cycle de vie complexe. En dépit de leur intérêt écologique, culturel et économique, les poissons amphihalins sont en déclin depuis des décennies dans de nombreuses régions du monde. Dans cette étude, nous avons étudié l'évolution des comptages de cinq taxons amphihalins en France sur une période de 30 ans en utilisant les données de 43 stations de comptage situées dans 29 rivières et 18 bassins versants. Notre hypothèse est que les comptages de ces espèces ont évolué de manière contrastée entre les bassins versants. Nous avons également testé l'effet de cinq facteurs susceptibles de contribuer aux tendances observées : le bassin versant, la latitude, la présence de pêcheries commerciales, l'amélioration de la continuité écologique et la présence d'un programme de déversement pour le saumon. Nous avons trouvé des tendances contrastées dans les comptages de poissons entre les espèces à l'échelle nationale, certains taxons étant en augmentation ( Anguilla anguilla et Salmo trutta ), certains ne montrant qu'une légère augmentation ( Salmo salar ) et d'autres étant en déclin ( Alosa spp. et Petromyzon marinus ). Pour chaque taxon, à l'exception d' Anguilla anguilla , nous avons mis en évidence un effet bassin versant important indiquant des tendances contrastées entre les bassins ou les stations de comptage. Cependant, nous n'avons trouvé aucun effet significatif des caractéristiques du bassin versant pour aucun des taxons étudiés.
The nitrate-induced photodegradation of chlorotoluron was demonstrated to occur efficiently in natural water through two series of experiments in outdoor aquatic mesocosms. During the first campaign, ...it was shown that the pesticide degradation kinetics was clearly dependent on nitrate concentration. This parameter also influenced the accumulation of the first- and second-generation byproducts, including predominantly N-terminus oxidation products and nitro-derivatives of the phenyl ring. The latter compounds, specific to the NO3 − -induced photoprocess, appeared particularly abundant as compared to laboratory-simulated sunlight irradiation conditions. During the second campaign, a dual day−night sampling was achieved, which demonstrated the almost exclusive role of photodegradation versus biodegradation.
Atlantic Salmon (
) is an anadromous migratory species adapted to cool temperatures. It is protected by the Bern convention and by the European Habitats Directive. It has been listed as vulnerable by ...the French IUCN Red List. Salmon decline is the result of combined and cumulated, mainly anthropic, causes: climate change, increasingly high number of impoundments, degradation of water quality and habitat and over-exploitation by fisheries. Monitoring of this species has been carried out on three rivers in France (Southern part of the distribution area) to produce data and knowledge (growth, precocious maturity, survival) for stock management.For 24 years, a specific and standardised electric fishing protocol has been used to target young-of-the-year (0+ parr) Atlantic salmon. Sampling was restricted to areas with shallow running water that flows over a coarse bottom substrate, i.e. the preferred habitat of young salmon. This monitoring and inventory of growing areas thus allows assessment of juvenile recruitment and provides baseline data required to calculate total allowable catches (TACs).
The dataset currently consists of 47,077 occurrence data points from 105 sites spanning up to 24 years in three different watersheds in France. Beyond our project, this dataset has a clear utility to research since it associates abundance measurements with the measurement of biological traits and the collection of tissue samples. It allows for current and retrospective characterisation of individuals or populations, according to life history traits and genetic features in relation to changes in environmental conditions. The fact that the monitoring takes place in France, the southern part of the distribution area, over 24 years, makes the dataset particularly relevant for climate change studies.
Electrofishing is widely used to survey fish communities in freshwater, but uncertainties remain about electrotaxis (i.e. swimming toward the electrode) and the efficiency with which it catches ...decapod species. This three-part study was performed to define effective electrofishing settings for mixed communities of freshwater decapods and fish species. First, we studied the behaviour of five species of swimming decapods (Caridae) when exposed to four waveforms (direct current (DC) or pulsed direct current (PDC) at 2, 5 or 40 Hz) and two power density settings (low (30 µW.cm−3) or high (80 µW.cm−3)) in the laboratory. DC at low power density and PDC-2 Hz at high power density induced significantly more electrotaxis than the other settings. We then tested three electrofishing settings (low power DC (DClp), high power DC (DChp) and high power 40 Hz PDC (PDC40hp)) under natural conditions using the depletion method (with three passes) in enclosed sections of a shallow stream, followed by complete removal of bottom substrate and aquatic vegetation to catch the remaining individuals. DClp consistently detected all shrimp (nine species) and fish (seven species) after two electrofishing passes, but the two other settings did not. DC performed better than PDC for estimating the abundance of shrimp (80% vs. 70% of individuals caught, respectively) and fish (90% vs. 70%, respectively) after three electrofishing passes. Using depletion models, DClp gave the most accurate estimates of abundance for shrimp and fish species. Finally, we assessed the ability of three-pass DClp electrofishing to estimate abundances in nine shallow and coarse-substrate Caribbean streams. More than 10,000 shrimp from 10 species and 1600 fish from 8 species were caught and examined. We observed a correlation between estimated and total abundances after complete removal of bottom substrate and aquatic vegetation in the enclosed stream sections, except for small (≤ 20 mm long) shrimp. The fish mortality rate due to electrofishing was 0.22%, and only one species (Eleotris perniger) showed evidence of spinal damage (4.4% of individuals) based on ultrasound analysis of the spinal column. Thus, we recommend using DClp (30 µW.cm−3) to survey sympatric communities of shrimp and fish species in shallow, coarse-substrate tropical streams.
•French Guiana biodiversity was explored for the search of novel botanical insecticidal products.•452 extracts from 85 plant species were tested for larvicidal activity against Aedes ...aegypti.•Bioassays included both insecticide-susceptible and -resistant Ae. aegypti populations Sextonia rubra wood extract and its main components were highlighted as promising products.•Correlations between extracts larvicidal activity and plants chemical defense were investigated.
Natural products have proven to be an immeasurable source of bioactive compounds. The exceptional biodiversity encountered in Amazonia, alongside a rich entomofauna and frequent interactions with various herbivores is the crucible of a promising chemodiversity. This prompted us to search for novel botanical insecticides in French Guiana. As this French overseas department faces severe issues linked to insects, notably the strong incidence of vector-borne infectious diseases, we decided to focus our research on products able to control the mosquito Aedes aegypti. We tested 452 extracts obtained from 85 species originating from 36 botanical families and collected in contrasted environments against an Ae. aegypti laboratory strain susceptible to all insecticides, and a natural population resistant to both pyrethroid and organophosphate insecticides collected in Cayenne for the most active of them. Eight species (Maytenus oblongata Reissek, Celastraceae; Costus erythrothyrsus Loes., Costaceae; Humiria balsamifera Aubl., Humiriaceae; Sextonia rubra (Mez) van der Werff, Lauraceae; Piper hispidum Sw., Piperaceae; Laetia procera (Poepp.) Eichl., Salicaceae; Matayba arborescens (Aubl.) Radlk., Sapindaceae; and Cupania scrobitulata Rich., Sapindaceae) led to extracts exhibiting more than 50% larval mortality after 48 h of exposition at 100 µg/mL against the natural population and were considered active. Selectivity and phytochemistry of these extracts were therefore investigated and discussed, and some active compounds highlighted. Multivariate analysis highlighted that solvents, plant tissues, plant family and location had a significant effect on mortality while light, available resources and vegetation type did not. Through this case study we highlighted that plant defensive chemistry mechanisms are crucial while searching for novel insecticidal products.
French Guiana biodiversity was explored for the search of novel larvicidal products against both insecticide-susceptible and -resistant Aedes aegypti populations. Display omitted
In the last 10 years, many atypical novel members of Brucella species have been reported, including several Brucella inopinata‐like strains in wild‐caught and “exotic” amphibians from various ...continents. In 2017, a strain of Brucella was isolated for the first time in animals from a French farm producing frogs—Pelophylax ridibundus—for human consumption and identified as B. microti‐like. Following this first isolation, investigations were performed in this farm as well as in the farm of the research unit that provided the domestic frog strain to estimate the prevalence of B. microti‐like infection and its presence in the surrounding environment. Farming practices were investigated and samples including frogs at different development stages, surface tank swabs, water, feed and soil were analysed by real‐time PCR and bacteriological methods. High B. microti‐like prevalence values (higher than 90%) were obtained in frog samples in the commercial farm, and its presence was highlighted in the environmental samples except feed. In the research unit farm, B. microti‐like species was also isolated and detected in frog and environmental samples. These results show that B. microti‐like organisms are able to colonize amphibians and persist in their environment. Its presence could constitute a possible risk for consumers and workers proving the importance of assessing the zoonotic and pathogenic potentials of these new and atypical Brucella species.
Sextonia rubra is an Amazonian tree known for the larvicide activity of its wood extracts against Aedes aegypti. However, the lipophilic character of this extract presents an obstacle to the ...development of vector management products. The purpose of this study was to assess the feasibility, efficacy, and selectivity of a water-soluble formulation based on a S. rubra wood extract characterized by its larvicidal compounds rubrenolide and rubrynolide. Using reference and wild strains, larval mortality, oviposition behavior, hatching response, and fitness of mosquitoes exposed to the extract were evaluated. Laboratory eco- and cytotoxicity bioassays were performed concurrently. The extract showed larvicidal efficacy and no repulsive effect on oviposition, thus supporting its use in the treatment of breeding sites. The formulation exhibited strong acute toxicity, leading to 100% larval mortality in 2–4 days in either the dry or rainy season at a test dose of 102 µg/ml under semi-operational conditions, with residual activity maintained during the 5 weeks of testing. The formulation allowed for a noticeable gain in selectivity compared with the extract, with lower immobilization rates for Daphnia magna and Chironomus riparius, and no significant toxicity towards human cell lines (IC50 > 100 µg/ml). These results highlight the potential of the S. rubra-based formulation for the management of Ae. aegypti larvae, including strains showing resistance to conventional insecticides.
Numerous studies have documented a change in the phenology of migration of diadromous fish in response to climate change. Only few studies have, however, been conducted simultaneously for multiple ...species and at a large spatial scale.
We investigated the change in the timing of upstream migration of diadromous fish species in France. We used an original dataset collected from 40 fish‐counting devices in 28 French rivers over 10–30 years for five diadromous taxa: Alosa spp., Anguilla anguilla (with a distinction between glass eel and yellow eel), Petromyzon marinus, Salmo salar, and Salmo trutta.
Except for glass eel, we found that taxa shifted their migration for earlier arrival dates. This result is consistent with numerous studies reporting advancement of the phenology of species life‐events. On average, we highlighted a phenological change of −2.3 days per decade (min = −0.2, max = −3.7). Moreover, the North Atlantic Oscillation Index, sea surface temperature, air temperature, and river discharge were found to explain the timing of upstream migration of diadromous fish taxa, highlighting the importance of factors acting at different spatial scales.
Given the important phenological changes observed in our study and more widely in the scientific literature, we recommend that managers incorporate these changes into the management rules; in particular, in the case of dams whose migratory transparency (i.e. the possibility for the fishes to cross the dam) is ensured by adaptive water management and gate operations.
This study benefited from large‐scale monitoring of migratory phenology of multiple species and environmental variables. These monitoring data are valuable and could allow better predictive modelling of the response of species to climate change.
Four new sesquiterpene alkaloids (1–4) with a β-dihydroagrofuran skeleton and a new triterpenoid (5) were isolated from an ethyl acetate extract of Maytenus oblongata stems. Their structures were ...elucidated using 1D and 2D NMR spectroscopy as well as MS and ECD experiments. The M. oblongata stem EtOAc extract and the pure compounds isolated were tested for larvicidal activity against Aedes aegypti under laboratory conditions, and compounds 2 and 3 were found to be active.
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