Balkhash Perch

The Balkhash perch resembles its congeners, the European perch (Perca fluviatilis) and the yellow perch (Perca flavescens), in its general profile and its modest size, reaching a maximum total length of 50 cm and weight of 1.5 kg. Like them it has spines on the tips of the opercula and in the dorsal, pelvic, and anal fins, as well as sharing a similar dentition. It also shares with them the ctenoid scales that lend a rough texture to the fish when handled. It differs in its longer, thinner build and lower first dorsal fin; and whilst its congeners have marked vertical dark bars on their bodies, the Balkash perch normally lacks such markings when it attains its larger sizes and is of a much paler hue. When vertical bars are present they are usually much less visible than in the other Perca species. There are, however, populations in which such bars are visible, along with coloured fins reminiscent of the other Perca species. The body is covered with larger scales than those of its congeners, with 44–54 on the lateral line. It is a markedly variable species, occurring in ecomorphic forms that have been termed 'pelagic', 'shoreline', 'riverine', and 'dwarfish'. In other locations forms that grow at different speeds have been distinguished, or in another case 'lake' and 'reed' forms that differed in colour and body shape. …

FishBase reports only that the Balkhash perch is found in Lake Balkhash and Lake Alakol, both in Kazakhstan. N. S. Mamilov, a zoologist working in Kazakhstan, has described it as endemic to "the Balkhash lake watershed, including the Alakol Lakes system", and has mapped the presence and absence of the species in various rivers and other water bodies in that area. Maurice Kottelat, in his 1996 IUCN assessment states that the species' range also extends into parts of this catchment area that are in China, though no data on such populations were available. The Balkhash perch was introduced into the Nura and the Chu rivers, but in neither case was this a success.