Alburnus istanbulensis

Alburnus istanbulensis is distinguished from related species around the Aegean and Black Seas by the origin of the anal fin being about 1⁄2 to 1+1⁄2 scales behind the base of the dorsal fin; by the lateral line having between 57 and 63 pored scales; the anal fin has between 13 and 15+1⁄2 branched rays; in breeding fish the bases of the pectoral and pelvic fins are hyaline or grey; the ventral keel is exposed with 8 to 12 scales in front of the anus; the caudal peduncle has a depth of around twice its length; and breeding males develop a few, large tubercles. The Marmara shemaya has a maximum standard length of 18 cm (7.1 in).^[5]

Alburnoides istanbulensis is nearly endemic to the Marmara region of Turkey, where it is found in coastal river systems draining to the Black Sea, Sea of Marmara and Aegean Sea basins. In the Black Sea, it occurs from the Papuç River east to the Sakarya River, while along the northern coast of the Sea of Marmara it occurs in the Alibey, Kâğıthane and Karasudere rivers near Istanbul. It is also found in rivers draining to the Sea of Marmara throughout its southern coastline, as well as in the Biga Peninsula where this species is known from a afew river systems draining into the Aegean Sea, with the Tuzla River being the southern limit of its distribution. The Marmara shemaya is found in rivers and lakes, where it forages near the surface. In the spawning season these fishes migrate to the upper reaches of the smaller tributaries to spawn in riffles over fine substrata, like gravel.^[1]