The use of native piscivorous fishes for the eradication of the invasive Chinese Sleeper, Perccottus glenii

The chief aim of invasive species management is to prevent biological invasions by taking measures for suppressing or eradicating potential invaders. Biological control as a management tool is frequently implemented to reduce the population size, adverse ecological impacts, and dispersal of invasive species. The efficacy of biological control measures in managing the Perccottus glenii population was assessed in four small lakes of Lithuania. The biocontrol was carried out by introducing the native piscivorous fishes Esox lucius and Perca fluviatilis into the invaded water bodies for two successive reproductive seasons. The stocking of these fishes led to an instant reduction in P. glenii abundances, and the outcome of the repeated stocking was complete disappearance of the species from the water bodies investigated. Our study proves that native predator fishes can be successfully used for eradicating well-established P. glenii populations in small eutrophic lakes. We hope the current study results will contribute to developing risk-commensurate methodologies for the control of invasive P. glenii populations in small water bodies

The influence of introduced ponto–caspian scuds and opossum shrimps on perch (perca fluviatilis) diet and growth rate in the lakes of lithuania

SUMMARY The influence of the introduced Ponto-Caspian scuds and opossum shrimps on perch (Perca fluviatilis) diet and growth rate in the lakes of Lithuania The purpose of this study was to examine perch (Perca fluviatilis) feeding habits and diet differences between two types of lakes that differ in having and lacking abundant littoral populations of introduced Ponto-Caspian opossum shrimps and scuds. The growth of the perch has been performed in order to answer whether introduced crustaceans really improve fish food basis in lakes. 1104 individuals were used to perform their growth rate analysis. 861 individuals were used to clear their diet. Fish and littoral benthic animal’s samples were collected in 2004 – 2006 summer and fall seasons in 10 Lithuanian lakes (Dusia, Daugai, Asveja, Žeimenys, Šakarvų, Baluošai, Nedingis, Lavysas, Plateliai and Beržoras). Analyses show that perches consume introduced Ponto-Caspian crustaceans from their first year. Kruskal-Walis ANOVA test show significant general lake effect on consuming rate of both scuds and opossum shrimps when comparing between three types of lakes that differ in littoral scuds and opossum shrimps population size. There was bigger consuming rate in lakes with larger crustacean’s populations in four different age groups of perch. We found significant correlations between relative biomass of littoral scuds in the benthic communities and in the perch stomach in three different age groups of perch. However we failed to find this correlation in third year old age group of perch. Multiple regressions showed that age of perch (A) and relative biomasses of littoral scuds in the benthic communities (BB) have significant influence on relative biomass of scuds in the perch stomach (BP): BP = 0,42005 BB + 3,97621 A – 5,33209. We failed to find significant correlation between benthic animal’s diversity index and feeding niche breadth of perch in studied lakes. There were no significant differences of feeding niche breadth of perch in three lake groups having or lacking abundant populations of introduced crustaceans in different age of perch also. We found that perch feeding niche breadth dependent from perch age. Perch age has significant influence on perch feeding breadth (two-way ANOVA p < 0,05). However, there were no significant differences in feeding niche breadth between different age groups of perch in studied lakes. The feeding selectivity of young perch showed that those lakes that are settled by abundant populations of introduced crustaceans were not similar. We found significant difference in first three years growth of perch between Daugai and Baluošai lakes. These lakes are similar by their abiotic conditions but separate in having and lacking abundant populations of introduced Ponto-Caspian crustaceans. The better growth was in Baluošai Lake that lack abundant littoral scuds and opossum shrimps populations. Thus there was no evidence to confirm that large populations of introduced crustaceans have positive effect on juvenile perch growth rate. In conclusion, our analysis shows that abundant introduced crustacean’s populations do not significant changing feeding niche breadth and feeding selectivity of young perch. Moreover these abundant invasive populations have no positive effect on young perch growth rate

The impact of introduced Ponto-Caspian mysids (

Paramysis lacustris was introduced into Lithuanian lakes in the middle of the 20th century. It was assumed that P. lacustris will enhance efficiency of primary production utilization and channelling of primary production towards higher trophic levels, i.e. commercially important fish species. However, at the time of P. lacustris introduction, there were no reliable data about its trophic position in lakes. Thus, P. lacustris was considered to have no or little impact on native ecosystems. Until now, there is a gap in the knowledge of the trophic role and potential impacts of P. lacustris on local food webs in lakes. Here we investigated the impact of P. lacustris on the food chain length of its potential predator Perca fluviatilis in temperate lakes. In this study, gut contents and stable isotope analyses were performed to assess the diet and trophic position of P. lacustris and P. fluviatilis in lakes with and without invasive mysids. The results obtained revealed that P. lacustris consumes a significant amount of animal prey and occupies the third trophic level in lake littoral zones. Furthermore, our results showed that P. lacustris might enhance the food chain length for at least some zooplanktivorous fishes. Overall, the assumption that P. lacustris invasion has no whole-ecosystem consequences, as it was thought before its introduction, is not correct

Experimental evidence that the invasive snail potamopyrgus antipodarum (Gray, 1843) survives passage through the digestive tract of common riverine fish

Potamopyrgus antipodarum is one of the most widespread invasive species worldwide and its expansion is ongoing. Although the snail has already been documented as surviving the digestive tract of various fish, there is insufficient data on potential riverine fish predators of P. antipodarum and of the ability of the snail to survive digestion by these fish. Lotic ecosystems are unfavourable for the upstream spread of this species by active movement and thus it is suspected that benthivorous riverine fish facilitate such upstream dispersion. In general, the results of this study indicated that P. antipodarum is not a preferable food object for the studied riverine fish. The study did indicate, however, that the invasive snail is capable of surviving the digestive tract of all the studied fish. As accidental consumption of abundant P. antipodarum with other food objects has already been documented, this study suggests that riverine fish can act as potential secondary dispersion vectors, facilitating the upstream dispersion of the snail

Delayed expansion of Ponto-Caspian gobies (Pisces, Gobiidae, Benthophilinae) in the Nemunas River drainage basin, the northern branch of the central European invasion corridor

During the past few decades, rapid expansion of Ponto-Caspian gobies has been observed in the rivers connected to the central European invasion corridor. The Nemunas River catchment has been connected to this corridor for more than two hundred years, yet there is no evidence of Ponto-Caspian gobies in the Nemunas River. This study aimed to assess the presence of Ponto-Caspian gobies within the Nemunas River and its main tributaries, specifically in the Lithuanian part of the Nemunas and Neris Rivers, which may serve as possible routes for these fishes’ expansion. Of all the presumptive Ponto-Caspian goby species only Neogobius fluviatilis (Pallas, 1814) and Neogobius melanostomus (Pallas, 1814) were caught. The relative abundance and biomass of both species was very low. The pilot analysis of piscivorous fish diet revealed that N. fluviatilis is already selectively consumed by Esox lucius. Although both species can reproduce and sustain viable populations in the Nemunas River, different scenarios for their future establishment within the Nemunas River drainage basin are predicted. The hypothesized distribution of N. melanostomus will remain restricted only to the outlets of the Nemunas River; while the distribution of N. fluviatilis in the future will be wider. We presume that the area colonised by N. fluviatilis will expand until the species establishes in the entire Nemunas River drainage system

Several decades of two invasive fish species (Perccottus glenii, Pseudorasbora parva) of European concern in Lithuanian inland waters; from first appearance to current state

Following their first appearance, the invasive fishes Pseudorasbora parva and Perccottus glenii have been in Lithuania for several decades. However, until recently, information relating to their distribution and secondary spread was limited. For this reason, suitable habitats for these fish species were surveyed for their presence across the entire country. Additionally, all previously reported records on the presence of these species were summarized. Results revealed P. glenii to be widely distributed within the country with abundant populations in habitats suitable for the species. The recent distribution of P. parva is restricted to only a few water bodies. It was shown that both species are associated with human mediated transfer, while no natural dispersal of these invasive species was observed. The results of this study suggest that the invasion of Lithuanian inland waters by P. parva and P. glenii is still ongoing, and their occurrence in numerous water bodies, which are still devoid of these species, now seems probable. Demonstrated vectors of P. parva and P. glenii introductions in Lithuania highlight the importance of controlling and screening human activities related to aquaculture, recreational angling and the ornamental fish trade in order to restrict further P. glenii and P. parva expansion in this region

Predator-prey interactions between a recent invader, the Chinese sleeper (Perccottus glenii) and the European pond turtle (Emys orbicularis): a case study from Lithuania

The European pond turtle, Emys orbicularis, is a critically endangered species in most European countries. Habitat degradation and fragmentation are considered the main reasons for the decline of E. orbicularis. However, the spread of invasive species may also contribute to the disappearance of E. orbicularis populations. We examined the range overlap and predator-prey interactions between the invasive Chinese sleeper, Perccottus glenii, and E. orbicularis through controlled experiments and in field studies. Field surveys showed that both species occupied similar habitats. Predator-prey experiments suggested that newly hatched turtles are resistant to P. glenii predation. Conversely, adults of E. orbicularis consumed juvenile P. glenii even when other food sources were available. Overall, these findings suggested that E. orbicularis is not among the potential prey organisms in the diet of the invasive P. glenii, and that this fish does not directly contribute to the decline of E. orbicularis in Europe