Spatio-temporal dynamics of the expansion of rotan Perccottus glenii from West-Ukrainian centre of distribution and consequences for European freshwater ecosystems

Abstract

The invasive fish rotan or Amur sleeper, Perccottus glenii (Perciformes, Odontobutidae), arrived in Western Ukraine during the stocking of commercial cyprinid fish in the 1960s. Three periods were identified in its expansion. Period I: during the first two decades post-arrival, the fish was restricted to the upper section of a local river basin. Period II: rotan penetrated the adjacent river basins and over the following two decades, it rapidly self-distributed over huge distances, using rivers as long-distance, one-way natural corridors (natural conveyors). This expansion resulted in the invasion of many European river systems including the Danube, Dniester, western part of the Dnieper basin, Southern Bug (all belonging to Black Sea basin), and the Vistula (Baltic Sea basin). During colonization, rotan was found in Lviv, Zakarpatie, Volynskaya, Povno, Ivano-Frankovsk, Chernovtsy and Khmelnitskiy provinces of Western Ukraine, as well as in territories of south-western Belarus, Poland, Slovakia, Hungary, Serbia, Bulgaria, Romania, Croatia, and Moldova. This invader demonstrated comparatively rapid expansion from riverheads to downstream river mouths, but slower or negligible expansion upstream in tributaries. This example of the West-Ukrainian centre of distribution demonstrates the significance of upper parts of river basins for rapid distribution of this species, as well as the important function of rivers in crossing country borders. Period III relates to the period from approx. 2005 to the present day. During this period, perceived to be the longest in terms of colonization, its invaded range extends to tributaries and isolated water bodies filling gaps in areas between already colonized main rivers. Rotan did not reach high densities in the main river channels or deep, well-oxygenated lakes because of the presence of native fish predators. However, this alien species did form numerous dense populations in shallow lentic water bodies. The expansion of rotan may lead to adverse economic impacts upon European aquaculture farms, as well as predictable, ecological consequences for populations of some native European aquatic animals including invertebrates, fish and amphibians. Rotan has the potential to also influence adjacent terrestrial ecosystems. A review of rotan and native species interactions is presented.