Non-native and translocated freshwater fish species in Turkey

Abstract

Turkey is a hotspot of freshwater fish diversity and endemism, holding a unique ichthyofauna containing distinct European and Asian elements. Currently, 78 endemic species are recognised from Turkey, 65 of which are classified as Critically Endangered or Endangered. Habitat degradation, pollution, and the introduction of non-native fishes are the greatest threats to this unique ichthyofauna. We compiled data on the introduction and distribution of freshwater fishes in Turkey, both nonnative and translocated, based on historical accounts and recent surveys. Thirty fish species have been introduced, 11 of which are translocations within Turkey. The overall establishment success was 64% (44% for non-natives and 100% for translocated species). New species continue to be introduced at a rate of 4.8 species per decade, of which 3.1 species establish per decade. Fisheries and aquaculture are two main vectors of deliberate introduction, but the contaminant of stockings is the primary pathway for secondary spread, in particular for Carassius gibelio, Pseudorasbora parva and Lepomis gibbosus. Natural dispersion of species introduced into neighbouring countries through trans-boundary river systems is highlighted as the most likely pathway for future species introductions. We discuss the management options available and outline how these can be incorporated into freshwater fish conservation and non-native fish management programmes. Education, public awareness and information are central components to reduce current rate of fish introductions in Turkey.