Abstract
Perca schrenki is endemic to the Balkhash ichthyogeographic province in Kazakhstan and historically inhabited various ecological regions within the basin. Its distribution has been considerably reduced because of the introduction of many other species, although it still occurs in the Alakol lakes, where a fishery thrives, and in some outlying areas of the basin. The Balkhash‐Ili population of P. schrenki was considered endangered several years ago, but, in fact, these populations are now extirpated. During the 1960s, P. schrenki was introduced outside of its native range. Populations now exist in the basins of the Rivers Nura, Olenty and Chu, as well as in some lakes in northern Kazakhstan. This expansion has resulted in hybridization between P. schrenki and P. fluviatilis‐species that were previously reproductively isolated.