The urbanization process deeply affects rivers and streams, with numerous impacts, such as the discharge of sewers, dams, and pipework, causing profound changes in the water bodies characteristics and in their biota. In this scenario, the silting of rivers suffers one of the most impactful changes, as it undergoes a reduction in the depth and width of the rivers, triggering physical and chemical changes in the water, as well as in the structure of fish population, its feeding and reproduction habitats. As a palliative measure, it is normal to carry out the desilting (dredging) of rivers, an activity that is also very impacting. Floodings are one of the main factors that demand dredging to be carried out. This review was made to analyze desilting activities, their effects on biota and migratory fish, as well as to evaluate the best management strategies and mitigation of impacts on fish population. The shifting and removal of sediment from the riverbed can cause burial and massive death of eggs and larvae, in addition to interfering in the upward and downward migration of eggs, larvae, and adults of migratory fish. In addition, breeding and feeding sites can be impacted by sediment movement, dredging, and deposition. Some actions minimize the impacts of the silting activity recovering riparian forests, inspect the use of soil on the banks, move urban settlements away, assess the dredging site, consider the spawning sites and reduce the suspension of bottom sediments, as well as choose the best equipment and time for the performance of activities. Therefore, the development of research on the effect of dredging of water bodies on fish would contribute to a better management of the activity.

The urbanization process deeply affects rivers and streams, with numerous impacts, such as the discharge of sewers, dams, and pipework, causing profound changes in the water bodies characteristics and in their biota. In this scenario, the silting of rivers suffers one of the most impactful changes, as it undergoes a reduction in the depth and width of the rivers, triggering physical and chemical changes in the water, as well as in the structure of fish population, its feeding and reproduction habitats. As a palliative measure, it is normal to carry out the desilting (dredging) of rivers, an activity that is also very impacting. Floodings are one of the main factors that demand dredging to be carried out. This review was made to analyze desilting activities, their effects on biota and migratory fish, as well as to evaluate the best management strategies and mitigation of impacts on fish population. The shifting and removal of sediment from the riverbed can cause burial and massive death of eggs and larvae, in addition to interfering in the upward and downward migration of eggs, larvae, and adults of migratory fish. In addition, breeding and feeding sites can be impacted by sediment movement, dredging, and deposition. Some actions minimize the impacts of the silting activity recovering riparian forests, inspect the use of soil on the banks, move urban settlements away, assess the dredging site, consider the spawning sites and reduce the suspension of bottom sediments, as well as choose the best equipment and time for the performance of activities. Therefore, the development of research on the effect of dredging of water bodies on fish would contribute to a better management of the activity.

SOINSKI, T. A. Restoration of the fish assemblage in a stream after dam rupture and ecological restoration process. 2021. 121 f. Dissertação

The presence or absence of a fish species may be associated with the physical and chemical characteristics of the water, in addition to the state of preservation of the riparian zone. This study examined whether the taxonomic fish composition in an urban river varies along three riparian zone preservation conditions: preserved, intermediate preservation and degraded. Six urban stretches of the Sorocaba/São Paulo River were selected for this study, with monthly sampling being carried out from June 2019 to February 2020. The samplings were carried out with the aid of a sieve, dip net, and trawl. Regarding the types of margins and environmental variables, the Principal Component Analysis explained 97.49% of the data variation, axis 1, which explained 91.85% of the total variation, was formed by the variables conductivity and total dissolved solids. Axis 2, which explained 5.64% of the variation, was formed by Sun Rays% and Siltation%, being inversely proportional to Riparian Forest%. For the ichthyofauna, the samples consisted in 50,983 fish distributed in 5 orders, 8 families, and 12 species. Cyprinodontiformes had the highest abundance, with 96.96% of the total number of individuals, followed by Siluriformes (2.39%), and the sum of the other orders did not reach 1% of the total collected. According to each type of margin, it was possible to register 11,592 individuals for the Margin A – preserved, with S=8 species, being 2 exclusive (Corydoras flaveolus and Hoplosternum littorale) and 3 exotic (Coptodon rendalli, Pterygoplichthys ambrosettii, and Poecilia reticulata), the latter was dominant in all types of margins. For Margin B – intermediate preservation, 19,645 individuals were sampled, with S=5 species, no exclusive species, only exotic and more tolerant native species such as Hoplias malabaricus and Hypostomus ancistroides. For Margin C – degraded, 19,746 individuals were recorded, the largest number of species (S=10), 3 were exclusive to this type of margin (Psalidodon fasciatus, Rhamdia Quelen, and Geophagus brasiliensis). The pairwise comparison (similarity percentage) showed that the assemblage structure was different for the types of margins. The Canonical Correspondence Analysis explained 92.46% of the total data variation, showing the relationship of species to environmental data. It is evident the importance of preservation of micro-habitats still present in the locals sampled, since different anthropic pressures cause great loss of diversity, especially for native and more sensitive species.

The presence or absence of a fish species may be associated with the physical and chemical characteristics of the water, in addition to the state of preservation of the riparian zone. This study examined whether the taxonomic fish composition in an urban river varies along three riparian zone preservation conditions: preserved, intermediate preservation and degraded. Six urban stretches of the Sorocaba/São Paulo River were selected for this study, with monthly sampling being carried out from June 2019 to February 2020. The samplings were carried out with the aid of a sieve, dip net, and trawl. Regarding the types of margins and environmental variables, the Principal Component Analysis explained 97.49% of the data variation, axis 1, which explained 91.85% of the total variation, was formed by the variables conductivity and total dissolved solids. Axis 2, which explained 5.64% of the variation, was formed by Sun Rays% and Siltation%, being inversely proportional to Riparian Forest%. For the ichthyofauna, the samples consisted in 50,983 fish distributed in 5 orders, 8 families, and 12 species. Cyprinodontiformes had the highest abundance, with 96.96% of the total number of individuals, followed by Siluriformes (2.39%), and the sum of the other orders did not reach 1% of the total collected. According to each type of margin, it was possible to register 11,592 individuals for the Margin A í  preserved, with S=8 species, being 2 exclusive (Corydoras flaveolus and Hoplosternum littorale) and 3 exotic (Coptodon rendalli, Pterygoplichthys ambrosettii, and Poecilia reticulata), the latter was dominant in all types of margins. For Margin B í  intermediate preservation, 19,645 individuals were sampled, with S=5 species, no exclusive species, only exotic and more tolerant native species such as Hoplias malabaricus and Hypostomus ancistroides. For Margin C í  degraded, 19,746 individuals were recorded, the largest number of species (S=10), 3 were exclusive to this type of margin (Psalidodon fasciatus, Rhamdia Quelen, and Geophagus brasiliensis). The pairwise comparison (similarity percentage) showed that the assemblage structure was different for the types of margins. The Canonical Correspondence Analysis explained 92.46% of the total data variation, showing the relationship of species to environmental data. It is evident the importance of preservation of micro-habitats still present in the locals sampled, since different anthropic pressures cause great loss of diversity, especially for native and more sensitive species.