Balkhash marinka
The Balkhash marinka, is a species of ray-finned fish in the genus Schizothorax of the family Cyprinidae which is found in the Lake Balkhash basins in Kazakhstan and Xinjiang. It uses gravel substrates for spawning and the unshed roe is toxic.
Biology
There are two distinct forms of the Blakhash marinka, a riverine form, and a faster growing migratory lacustrine form, however, both forms spawn in fast flowing currents over gravel beds. The females are sexually mature at4-11 years of age, the males at 3–8 years old. They are a fecund species and may lay between 12,000 and 122,500 eggs, although normally32,000 to 67,000 are laid in a spawning, the amount being dependent on the demographic make up of the spawning stock. Each egg is 2.3 mm in diameter. At a water temperatures ranging from 15 °C to 16 °C, and under controlled conditions, the eggs take 5 days to hatch. After six days from hatching the larval fish reach lengths of approximately 1 cm and has fully absorbed the yolk sac and starts to feed on plankton. By 25 days old they can be described as fry and have taken the form of small fish. When the fry grow to 16–30 mm they start to feed on small benthic animals and algae attached to the substrate. The unshed roe is toxic if consumed.There are three feeding types of Balkhash marinka. The form which occurs in mountain rivers feeds mainly on benthic organisms and does not feed on flying insects as its lower jaw is adapted to scraping algae and vascular plants off the substrate. The form living in lakes is also mainly a plant feeder while the form found in larger rivers is frequently a predator, especially if there are no other predatory fish present. This predatory type feeds mostly on benthic organisms, flying insects and on small fish such as stone loaches, as well as small terrestrial animals which fall into the stream, including vertebrates such as lizards. The rate at which the fish grows is depenent on the habitat and feeding type with those in mountain streams rarely growing to more than 1 kg and it reaches sexual maturity at a weight of 100 to 300 g. The lake form tends to be somewhat heavier, usually wighing 1.5 kg, and some individuals may grow to weights of 5–6 kg. The riverine form which is a facultative predator can grow to up to 12 kg, although normally specimens weigh 2 to 5 kg.