Wednesday 2nd of july – 16:30
16:30
Decadal trends in native and non-native fish assemblages in a large floodplain river in the Pacific Northwest, USA
AUTHORS
GREGORY Stan, PENALUNA Brooke, GIANNICO Guillermo, BOYER Kathryn
United-States
Short Abstract: Major declines and losses in biodiversity are occurring globally, and data for native and non-native fish assemblages in freshwaters, especially large rivers, are limited. We assessed the complete assemblage of 41 fishes along 240 km of the Willamette River, an 11th order river in Oregon, USA using consistent boat and backpack electrofishing methods over two decades. Abundance and species richness of native fish decreased longitudinally downstream, and abundance and richness of non-native fish increased downstream. The abundance of non-native fish was significantly greater in the period of 2021-2023 as compared to the previous decade, and the increase was greater in the downstream reaches of the river. Abundance of native fish was significantly lower in the period from 2021-2023, but the differences were small. Distributions of some species expanded or contracted. Accelerated restoration efforts in the Willamette River and rivers throughout the world are essential to protect and recover their native fish assemblages. Many restoration programs are focused on correcting the problems caused by past land uses and environmental degradation. Our success in restoring rivers and recovering native fish assemblages may be limited if we do not understand the processes that are changing and fail to anticipate the future river.
16:50
Exploring damming and restoration long-term effects on side channel biodiversity using macrofossils in river sediment cores
AUTHORS
DENDIEVEL André-Marie, RIQUIER Jérémie, MOURIER Brice, WINIARSKI Thierry
France
Short Abstract: This research aims at reconstructing long-term (post-1950) biodiversity changes on side channels by analysing macrofossils (plant, animal or abiotic remains < 5 mm) accumulated in sediment deposits. This approach relies on river cores dated by radionuclide along the Rhone River. Macrofossils, especially forest and aquatic taxa, provide a history of habitats and biodiversity since 1950, revealing three main hydro-ecological phases linked to river developments and management. The first phase, before dam construction, highlights a diversified riverine forest marked by black alder scales, strawberry seeds and wood fragments. The second phase, in the 1980s-1990s, indicates a transition to terrestrial ecosystems due to water diversion, and the expansion of nitrophilous plants. Then, after 2000, macrofossil data reveal new wetland and aquatic plants after channel restoration. The study of these bioindicators provide a valuable complement to sedimentological data and to plant inventories in order to analyse the evolution of riparian habitats following developments or restoration actions. This approach can help to define reference conditions and can be a tool improving the monitoring of alluvial wetlands, with a retrospective view.
17:10
When the Rhône changes, the Spirlin adapts: seasonal variations in metabolic and swimming performance of this little-known fish species
AUTHORS
WATSON Julia, SOUQUES Chloé, MORALES Anne, ZOPPI Océane, FABRA Maé, ROUSSEL Damien, CLAIR BOISSON Angeline, AVERTY Laëtitia, BASTIANINI Candice, CAPRA Hervé, LEBRUN Camille, LEGOFF Guillaume, MAIRE Anthony, DAUFRESNE Martin, TEULIER Loïc
France
Short Abstract: Ectotherms are organisms whose body temperature depends directly on environmental temperature, which makes them vulnerable to climate change. Temperature is an abiotic factor that is variable in space and time, and affects different physiological parameters in ectotherms, including their metabolism. Our aim was to study the effect of seasonal temperature fluctuations on the metabolism and swim performance of the spirlin, Alburnoides bipunctatus, which is known as a cold stenotherm but is found downstream of nuclear power plants in warmed conditions. Seasonal fluctuations lead to changes in hydro-climatic conditions, and with rising temperatures, questions arise regarding the ability of ectotherms to adapt to these variations. To investigate this, we fished spirlins downstream the Bugey nuclear power plant on the Rhône River, in February and in May before acclimatizing them to the temperature at which they were caught. We then measured (i) metabolic rate via using oxygen consumption as a proxy and (ii) swim performance in a swim tunnel at the acclimation temperature. Our results show that standard metabolic rate, maximum metabolic rate, and swim performance are enhanced in spring individuals compared to winter ones. These findings show an acceleration in metabolic processes due to a thermodynamic effect of temperature, resulting in increased energy availability for growth and reproduction.
17:30
Spatial heterogeneity and fish life traits correlated to freshwater fish population decline in France
AUTHORS
SANTOS Raphael, POULET Nicolas, BESNARD Aurelien
France
Short Abstract: Understanding the population dynamics of aquatic species and how inter-specific variation in demographic and life history traits influence population dynamics is crucial to define their conservation status and design appropriate protection measures. The abundance and biomass growth rates for 18 common European freshwater fish species were estimated using data spanning 1990–2011 for 546 sites across France. Spatial heterogeneity in abundance and biomass trends across France were assessed and correlations with life history traits were investigated.Amongst the 18 species, eleven of them have exhibited a significant decline in abundance and 14 species declined in biomass, seven remained stable or exhibited positive abundance growth rates; for four species, biomass was stable or increased. The main declines were observed in the Adour-Garonne and Loire-Bretagne RBDs, where management and conservation measures are urgently needed to halt the erosion of freshwater fish populations. In each of the 5 investigated RBDs, our results highlight areas where most of the common species we studied exhibited negative population growth rates. Of the demographic and ecological traits investigated, life-history strategy and maximum length were significantly correlated with species’ population growth rates, revealing that the decline mainly concerned large-bodied species with slow life-histories. These results focus on 18 common European species representing 94% of fish captured during the study period within the French national monitoring programme and underline that more attention should be paid to the decline in common species.