Deep Body Bitterling

About

Found across a broad range in China, northern Vietnam, and the Amur River drainage of Russia, this large bitterling, Acheilognathus macropterus, belongs to a fascinating group of fishes with one of the most unusual reproductive strategies in the freshwater world. In appearance it is a fairly deep-bodied, laterally compressed fish with silvery flanks, a grey dorsal surface, and a greyish lateral stripe running forward from the caudal peduncle. A dark spot marks the upper edge of the gill cover, and breeding males take on a faint pinkish flush with a white border on the anal fin. Like all bitterlings, this species depends on living freshwater mussels to reproduce. Females develop an extended egg-laying tube during breeding season and deposit eggs directly inside a mussel's gill cavity, while males fertilize them through the mussel's intake current. Because the specific mussel species this fish uses in its native range remains unidentified, captive breeding is considered unlikely under most circumstances. Outside of spawning season it is generally peaceful toward similarly sized tankmates, though small fish risk being eaten by adults. This is not a beginner's fish. It grows large, needs generous space, and turns up in the hobby only sporadically. Experienced keepers with the right setup will find it a genuinely interesting species to keep.