Variability of Coregonus peled (Gmelin, 1789) fecundity in the middle part of the Ob River (Western Siberia, Russia) and the influence of environmental temperature on it

Abstract

The peled, Coregonus peled, is a widespread species of the Coregonidae in Northern Eurasia. Its numbers remain relatively high throughout the Ob River basin. This species is environmentally plastic. Its fecundity varies widely, both across different water bodies and within the same water body during different observation periods. Hydrological conditions influence the reproductive capacity of peled, with higher fecundity in high-water years. This study aimed to analyze the fecundity of peled migrating upstream to the middle part of the Ob River for natural reproduction and detection the relationship between its fluctuations and environmental temperature. We identified that peled, which comes to spawn in the middle part of the Ob River, reaches sexual maturity at the age of three years. However, individuals aged five to six years form the basis of the spawning stock, comprising up to 70% of the total. The reproductive capacity of peled is highly variable. Individual absolute fecundity ranges from 11.3 to 58.0 thousand eggs, increasing with age, standard length, total weight, body weight, and Fulton and Clark indexes. Individual absolute fecundity ranges from 36 to 103 eggs per gram of body weight and correlates with total weight and Fulton indexes. Peled reproductive capacity indicators vary significantly between years. Overall, the individual relative fecundity of this species in age groups of 5+ years and older has decreased by 41–47% compared to the mid-20th century. There was a relationship between the reproductive capacity of peled migrating to the middle part of the Ob River for spawning and the environmental temperature in the lower part of the Ob River, where fish were feeding before the spawning migration begins: relatively high July temperatures are associated with lower individual absolute fecundity indicators for the most numerous age groups. Thus, global warming may have a negative impact on the reproductive capacity of peled in the Ob River basin.