Presently, invasive fish species become dominant in some freshwater waterbodies and watercourses of Central and South Vietnam in terms of abundance, successfully competing with native species for ecological niches and environmental resources. This can ultimately reduce the diversity of native fish communities and cause their further transformation. Loricariids are considered the main group of invasive fish species being a serious threat to tropical and subtropical freshwater ecosystems. In this regard, the distribution and morphology of suckermouth-armored catfishes (Pterygoplichthys spp.) in different habitats of Central and South Vietnam were studied. A total of 54 reservoirs belonging to the basins of 15 large and small rivers were surveyed. Specimens were examined for 7 meristic and 34 plastic characters. The osteological analysis of the axial skeleton of fish conducted using radiography. Morphological differences and a number of developmental anomalies of morphology were found in different armored catfish populations from Vietnamese waters. It is noted that deliberate or accidental introduction of suckermouth-armored catfishes and their further spread can have negative consequences for the biodiversity of Vietnam’s aquatic ecosystems.

Suckermouth armored catfish (Pterygoplichthys disjunctivus) is one of the most widespread invasive species in Vietnam. However, it is relatively unknown how the species underwent its divergent adaptations to varying local conditions and habitat types, an understanding of which is essential for managing its invasion in Vietnam. We addressed this by analyzing a large number of fish (662 samples) collected in lotic (Dinh River) and lentic (Suoi Trau Reservoir) habitats in southern Vietnam during one year. The allometric growth patterns estimated by von Bertalanffy growth functions were $L_t=483\left(1-e^{-0.71(t-0.40)}\right)$ in Dinh River and $L_t=346\left(1-e^{-1.01(t-0.62)}\right)$ in Suoi Trau Reservoir. The estimated fish ages were 2.9 to 4.2 years old with an average total length from 206.10 ± 2.09 mm in Suoi Trau Reservoir to 319.22 ± 3.29 mm in Dinh River. The percentage of fish with matured ovaries peaked in August (100%) and was lowest in February (<10%), indicating that these fish breed nearly all year round. The main reproductive season is April–October, with a peak in July–August, as indicated by the gonado-somatic index and monthly changes in the percentage of matured fish. The lengths at 50% maturity were 234.3 and 179.7 mm for females from lotic and lentic habitats, respectively. Lotic fish had a fecundity (4812 ± 383 oocytes/ind.) which was five times greater than that of lentic fish (841 ± 91 oocytes/ind.); however, the relative fecundity of the fish was not statistically different between the two habitats (≈13 oocytes/g). This result was consistent with the larger oocytes: 2.95 ± 0.04 and 2.58 ± 0.01 mm for fish from Dinh River and Suoi Trau Reservoir, respectively. The faster growth and bigger fish with higher fecundity in the lotic habitats suggest that their population growth can accelerate more quickly, potentially affecting local communities more than those in lentic habitats. Our study sheds light on substantial phenotypic divergences in the reproduction and growth of the suckermouth armored catfish between lotic and limnetic habitats in Vietnam.

The intrapopulation morphological and behavioral polymorphism of roach (Rutilus rutilus) and perch Perca fluviatilis) was studied. It was shown that marker indices for distinguishing intrapopulation groups are the size of the mouth opening and the index of the body shape in roach and the coefficient of pigmentation in perch. Based on analysis of the data of indices, it was found that there are two ecological groups—coastal and pelagic in populations of roach and perch. Several behavioral differences in individuals of various ecological groups were revealed. Comparison of the defense reaction of perch individuals belonging to various ecological groups was performed. The assessment of the effects of hydrodynamic activity on the survival of perch individuals belonging to various ecological groups was made. Differences in the swimming capacity of juvenile roach developing under conditions of biotopes of various types were established. Suggestions were made on the mechanisms of formation of intrapopulation groups of roach and river perch.

At present, invasive fish species dominate in terms of abundance and compete for environmental resources and ecological niches with native species in some freshwater waterbodies and...

The distribution of alien species of suckermouth armored catfishes (Loricariidae) in the water bodies and water streams of southern Vietnam has been studied. The taxonomic composition of suckermouth armored catfish is determined based on the data of morphological and molecular genetic analysis. Two species of armored catfishes, Pterygoplichthys pardalis and P. disjunctivus, as well as their interspecific hybrid (P. pardalis × P. disjunctivus), are found in the studied reservoirs and watercourses of southern Vietnam. Nowadays, the suckermouth armored catfish Pterygoplichthys spp. inhabits the basins of almost all major river systems of southern Vietnam.

Fish in the Volga-Kama River System (the largest river system in Europe) are important as a crucial food source for local populations; fish have the highest trophic level among hydrobionts. The purpose of this research is to describe the diversity of non-indigenous and native fish in the Volga and Kama Rivers, in the European part of Russia. This dataset encompasses data from June 2001 to September 2021 and comprises 1888 records (36,376 individual observations) for littoral and pelagic habitats from 143 sampling sites, representing 52 species from 42 genera in 22 families. The dataset has a Darwin Core standard format and has been fully released in the Global Biodiversity Information Facility (GBIF) under CC-BY 4.0 International license. The data are validated with several international databases such as FishBase, Eschmeyer’s Catalog of Fishes, the Barcode of Life Data System, and the SAS.Planet geoinformations system. Newly established populations have been found for several species belonging to the following Actinopteri families: Alosidae, Anguillidae, Cichlidae, Ehiravidae, Gobiidae, Odontobutidae, Syngnathidae, and Xenocyprididae. Therefore, this dataset can be used in the particular taxon species distribution analysis, which are especially important for non-indigenous species.