Invasive fish species in ichthioecosystems of Western Polissya of Ukraine

Purpose. To study ichthyocenoses, species composition and the current state of fish populations in water bodies of the Western Polissya of Ukraine by focusing on their changes under the effect of invasive fish species. Methodology. Ichthyological studies were carried out in natural and artificial water bodies for various purposes in the Western Polissya of Ukraine during 2007-2017. In particular, fish surveys were carried out using beach seins and gill nets with different mesh sizes in the karst lakes Svityaz and Pischane from the Shatskiy National Nature Park, channel lakes Lyubyaz and Nobel from the Pripyat River basin, right-bank tributaries of the Pripyat Rivers including Styr and Goryn Rivers, Khrinnitske reservoir from the Styr River basin, fish ponds of Bochanitsa village and Progress LLC (Goryn River basin). The material for the study were both the populations of native and invasive fish species. Findings. The results of our own studies and data of other authors highlighted the issue of the spread of invasive fish species in water bodies of the river-lake network of Western Polissya of Ukraine, presented the diagrams of the distribution of these fish in different water bodies of different origins of the above-mentioned region. Originality. The greatest threat to the abundance of aboriginal fish species in this region was found to be self-reproducing populations of the brown bullhead (Ictalurus nebulosus), Amur sleeper (Percсottus glenіi), stone moroko or topmouth gudgeon (Pseudorasbora parva), three-spined (Gasterosteus aculeatus) and nine-spined (Punguitius punguitius) sticklebacks. In particular, the composition of their gut content during the spawning period included 95% of eggs of fish species, which spawned in spring, as shown in the diagrams presented in this paper. Practical Value. The proposed measures to be carried out at the national and regional levels will help prevent the ingress of new invasions and mitigate the impact of the existing ones on the ichthyocenoses of the reservoirs of Western Polissya of Ukraine. Key words: ichthyocenoses, invasive fish species, aboriginal ichthyofauna, Western Polissya.

Fish Assemblage Shift after Japanese Smelt (Hypomesus nipponensis McAllister, 1963) Invasion in Lake Erhai, a Subtropical Plateau Lake in China

The introduction of non-native fish species is known to have adverse effects on aquatic ecosystems, but their effect on plateau lakes is not well studied. In this study, we examined the effect of the Japanese smelt (Hypomesus nipponensis) invasion on the fish assemblage in Lake Erhai, a subtropical plateau lake in southwestern China. Through cluster analysis and non-metric multidimensional scaling (NMDS), we found a significant fish assemblage shift: the population of sharpbelly (Hemiculter leucisculus) fell by 67% in catch per unit effort (CPUE) from 2.262 to 0.741; topmouth gudgeon (Pseudorasbora parva) fell by 52% from 0.61 to 0.29; and icefish (Neosalanx taihuensis) plummeted by 88% from 0.736 to 0.088. Meanwhile, the numbers for crucian carp (Carassius auratus) improved by almost 185% from 1.82 to 3.36. A Pearson correlation analysis showed that these four species significantly correlated with the invasion of the Japanese smelt: sharpbelly (−0.71), topmouth gudgeon (−0.71), icefish (−0.62), and crucian carp (0.81). This study documented the expansion of invasive fish and their effects on native species over time, thus providing a case study of invasive fish as well as a theoretical basis for further research into interspecies interactions.

A tale of an invader: Reconstructing the genomic history of invasive topmouth gudgeon (Pseudorasbora parva) populations.

Invasive species are significant contributors to global changes and constitute a severe threat to biodiversity. Yet invasions offer an incredible framework to understand how small and low-diverse introduced populations adapt to novel environmental conditions and succeed in colonizing large areas. However, due to the insufficient data on the origin of the first introduced propagule and the first stage of invasion, reconstructing a species’ invasion history is challenging. Here, we applied genetic clustering methods and explicit admixture tests combined with ABC models and Machine Learning algorithms to describe the phylogeography of native and invasive populations and infer the most probable demographic invasion scenarios of Pseudorasbora parva, a highly invasive freshwater fish and the healthy carrier of a novel lethal fungi-like pathogen (Sphaerothecum destruens), which is responsible for the decline of several fish species in Europe. We found that the current genetic structuring of the native P. parva range has been shaped by waves of gene flow originating from southern and northern Chinese populations. Furthermore, our results strongly suggest that the invasive genetic diversity is the outcome of past recurrent global invasion pathways of admixed native populations. Our study also illustrates how the combination of admixture tests, ABC, Machine Learning can be used to detect high-resolution demographic signatures and reconstruct an integrative biological invasion history.

Influence of nutrient enrichment on the growth, recruitment and trophic ecology of a highly invasive freshwater fish

The establishment probability of introduced alien fish can be context dependent, varying according to factors including propagule pressure and biotic resistance. The influence of nutrient enrichment on establishment outcomes of alien fishes is uncertain, yet this is a common anthropogenic stressor of many freshwaters. Here, the small-bodied alien topmouth gudgeon Pseudorasbora parva was used in mesocosms to experimentally test how a gradient of nutrient enrichment affected their growth rates, recruitment and trophic ecology. A ‘Control’ represented ambient, mesotrophic conditions, while treatments covered three levels of nutrient enrichment: low (eutrophic), medium (hypertrophic) and high (very hypertrophic). Each mesocosm was seeded with 6 mature P. parva (equal sex ratio) at the start of their reproductive season. After 100 days, length increments of the adult fish were significantly elevated in the low treatment, and these fish had also produced significantly higher numbers of 0+ fish compared to all other treatments. The trophic niche width of the mature fish was substantially higher in the control than the treatments, but this did not appear to confer any advantages to them in somatic growth rate or reproductive output. These results suggest that the nutrient status of receiving waters can have substantial impacts on the outcomes of fish introductions, where eutrophic conditions can assist the rapid population establishment of some alien species.

Morphometric features of topmouth gudgeon Pseudorasbora parva (Temminck & Schlegel, 1846) in the Hirfanlı Reservoir, Turkey

The aim of this study was to some morphometric characteristics of Pseudorasbora parva from Hirfanlı Reservoir, Turkey. A morphological analysis of 29 morphometric characters were performed. These characteristics head length; preorbital distance; eye diameter; postorbital distance; head depth; predorsal distance; prepelvic distance; preanal distance; pectoral fin–pelvic fin (P-V) distance; pelvic fin– anal fin (V-A) distance; body depth (18 perpendicular); dorsal fin (anterior end)-anal fin distance (Da-A); dorsal fin (posterior end)–anal fin distance (Dp-A); postdorsal distance; postanal distance; caudal (C) peduncle length (dorsal); caudal peduncle length (ventral); caudal peduncle depth; dorsal fin (D) base length; anal fin (A) base fin length; pectoral fin (P) length; pelvic (V) fin length; caudal upper lobe length; caudal fork length; caudal lower lobe length; dorsal fin length; anal fin length; gape. The samples were measured weight to the nearest 0.01g and total, fork and standard length to the nearest 0.01 mm. The total length (TL) ranged from 4.10 cm to 9.30 cm and body weight ranged from 0.600 to 7.137 g.Keywords: Pseudorasbora parva; topmouth gudgeon; morphometric properties; Hirfanlı Reservoir