The Balkhash perch (Perca schrenkii) is a species of perch endemic to the Lake Balkhash and Lake Alakol watershed system, which lies mainly in Kazakhstan. It is similar to the other two species of perch, and grows to a comparable size, but has a slimmer build and is lighter in colour. It has suffered a population decline which is blamed on introduced bream and predatory fish such as the Volga pikeperch. Discovery and first scientific description An expedition of Alexander von Schrenk to eastern Turkestan collected this species in 1842, and deposited preserved specimens at the Imperial Academy of Sciences in St. Petersburg; Karl Kessler's formal description was published much later, in 1874, after the rediscovered specimens were sent to him by Alexander Strauch. The description was included in an article on fishes collected by the later expedition to Turkestan of Alexei Pavlovich Fedchenko. The fish is named in honor of Alexander von Schrenck (1816–1876) the Baltic-German Russian naturalist and collector/explorer of Central Asia and northern Russia. Von Schrenck published observations about this species in 1840. Characteristics 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