Features of reproduction of whitefishes

Abstract

Based on features of reproduction, whitefishes (Coregonidae) differ from salmonids (Salmonidae) and graylings (Thymallidae). They differ from other salmonid fishes (Salmoniformes) in the following characteristics: they spawn, as a rule, during fall and winter; they do not construct spawning redds; their eggs are not protected; and substantial egg mortality is compensated by a high fecundity. The eggs of several whitefish species can develop in the conditions of “pagon” (within the ice). The main reasons for egg mortality at riverine spawning grounds are as follows: abnormalities during fertilization and development of the embryo, predation on the eggs, parasitic deceases, freezing of spawning grounds, and drift of the eggs from the spawning grounds. In addition (in the lakes), egg mortality can be caused by a deficit of oxygen, siltation, acidulation, and pollution of water. The survival of eggs of whitefishes in the Ural tributaries of the Lower Ob River in different years ranges from 0 to 93%. At a stable environment, the age of sexual maturation is connected with a certain body size of the fish. In the northern water bodies, the cycle of gonadal development can reach more than 1 year. Pollution of water by heavy metals, oil, and toxicants leads to serious anomalies of the reproductive system and to decreasing reproductive potential of the stocks.