3/17/2023 0 Comments Susannah flood swimming![]() ![]() Tagged fish were implanted with Vemco V6 dummy acoustic transmitters (DAT: 17.0 mm long × 6 mm diameter, 1.0 g in air). Three different experimental tag-treatment groups were established: control (no surgery), sham (surgery but no tag), and tagged (surgically implanted tag), with a range of 9–12 fish in each group. To assess the potential impact of “tag effect” on seaward-migrating Coho Salmon Oncorhynchus kisutch, presmolt juveniles were surgically implanted with acoustic transmitters followed by exposure to freshwater (FW, 0‰ salinity) or seawater (SW 30‰ salinity) for 24 h and then subjected to repeated critical swimming speed (U crit) trials. The research performed was structured in five chapters and included: (1) a compilation of Iberian inland fish trait data and corresponding reliability analysis of the different data sources (2) the analysis of swimming capacity of native and alien Iberian inland fishes using random forests models, generalised linear mixed model and linear models and (3) studies of the distribution patterns and niche characteristics of Iberian fish using species distribution models and the outlying mean index, as well as the analysis of relationships of these distribution patterns with fish traits using phylogenetic and non-phylogenetic approaches. Thus, this thesis aimed to evaluate the relationship of distribution patterns and traits of inland fishes, and to understand the ecological filtering with a special focus on hydrological alteration using the Iberian ichthyofauna as a study system. In fact, the Iberian Peninsula is one of the most impacted regions by dams (over 1500 large dams fragment Iberian rivers) and invasive species (32 established alien fish species). The Iberian Peninsula is a well-suited region to study the effects of climate, land use change and hydrological alteration on the distribution of native and alien fish species, due to its complex orography and diverse climate and ichthyofauna. However, there are few studies that evaluated its evolutionary relationship with other traits, with fish distribution patterns or with invasion success in freshwater ecosystems. For instance, swimming performance (often measured in the laboratory as critical swimming speed ) is a particularly important trait in aquatic organisms, mediating their fitness, habitat selection or survival. Thus, jointly studying species distribution patterns and species traits and their evolutionary history provides an essential link to better understand species’ responses to environmental change and biological invasions, and to design effective management tools and policies. Previous studies showed that the novel lentic habitats created by dams and habitat modifications occurring downstream of dams favour the establishment of alien fish, as many of them commonly prefer lentic habitats with warmer water temperatures compared with native fish. One of the most pervasive indicators of anthropogenic impacts on rivers is hydrological alteration caused by artificial barriers, which is known to reinforce the decline of local biodiversity and ecosystem services, and the species homogenisation of inland fish communities. Serious menaces to freshwater ecosystems are, for instance, habitat alteration, invasive alien species, pollution, water abstraction and climate change. Fresh waters are among the most biodiverse ecosystems globally but, at the same time, also the most threatened.
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