Alien freshwater fish species in the Balkans—Vectors and pathways of introduction

Abstract

Fish introductions, particularly in areas of high biological diversity and endemism, represent a major threat for biodiversity. In the Balkan Peninsula, 60 fish species have been introduced to date, of which 36 have become naturalized in inland waters. Since the Balkans are one of the world's 35 biodiversity hot spots, this large presence of alien fish species poses a serious threat for the stability of freshwater ecosystems and the survival of the native ichthyofauna and of aquatic biodiversity in general. The motivation for the introductions, and the historical timeline, varies among the Balkan states. Despite recent attempts to implement and align legislation aimed at preventing the introduction of potentially invasive species, and the implementation of rigorous controls of introductions and increased protection of open waters, the majority of current introductions remain intentional, primarily via aquaculture. This review article provides a historical overview of freshwater fish introductions, the motivation behind them and the current distribution of alien freshwater fishes in the Balkans. The ecological implications and future perspectives concerning alien fish species in the region are also discussed.

Cophylogenetic relationships betweenDactylogyrus(Monogenea) ectoparasites and endemic cyprinoids of the north‐eastern European peri‐Mediterranean region

“…It is a consequence of the glacial periods, when sea level dropped considerably and rivers of the northern Adriatic were connected together, which led to the exchange of many primary native fish species between the two peninsulas (Stefani, Galli, Crosa, Zaccara, & Calamari, 2004;Waelbroeck et al, 2002). However, many of the northern and north-eastern Mediterranean drainages are heavily affected by introductions of non-native freshwater species, including numerous cyprinoids (Bianco, 1995;Piria et al, 2018;Vukić, Eliášová, Marić, & Šanda, 2019), even the endemic ones being translocated often outside the native range (Bianco, 1995;Koutsikos et al, 2019). This could lead to the simultaneous introduction of their non-native parasite species, which can subsequently infect the native fishes (such as parasite Dactylogyrus, documented in Benovics et al, 2017).…”

Does rainbow trout justify its high rank among alien invasive species? Insights from a nationwide survey in Greece

“…In the following years, more (but not well‐documented) imports took place from Denmark, Poland, Spain and the USA, particularly by private trout farms, and several new mainly small in‐farm hatcheries were established. Around 80 small‐to‐medium scale trout farms have been established in rivers, streams and springs, mostly in the north‐western part of Greece (Piria et al, ), and these have been key introduction vectors of rainbow trout into natural systems (Liasko, Anastasiadou, Ntakis, Gkenas, & Leonardos, ). In addition, intensive stocking programmes have been put in place (and continue to date) by government agencies, and there is no doubt that many unrecorded introductions of rainbow trout in natural waters have taken place by local authorities and anglers.…”

The racer goby, Babka gymnotrachelus (Kessler, 1857) invades the Evros river: evidence of recent establishment in Greece

“…The racer goby Babka gymnotrachelus (Kessler, 1857) is native to the river catchments of the Black, Marmara and Caspian seas (Miller & Vasil'eva, 2003). Since the mid 1990s, this goby has invaded several central European rivers although it has not been recorded in Balkan rivers that enter the Mediterranean (Piria et al, 2017a;Koutsikos et al, 2019). Here we report on the recent discovery of B. gymnotrachelus in the transboundary Evros-Maritza-Meriç basin (hereafter Evros, the classical name), the largest river in the Balkans after the Danube.…”