Research Article: Biological and ecological aspects of South Caspian Spirlin (Alburnoides eichwaldii, De Filippi, ۱۸۶۳) from Tajan River, Northern Iran

Age, growth, and reproductive traits of the South Caspian Spirlin in the southern part of the Caspian Sea basin, Tajan, River, were investigated. A comprehensive study was conducted on ۶۶۳ specimens including ۲۲۶ females, ۲۹۷ males, and ۱۴۰ unsexed individuals with a total length ranging from ۲۵.۸۸ to ۱۲۱.۶۶ mm. The specimens were collected using an electrofisher at monthly intervals. The female-to-male sex ratio was calculated as ۱: ۱.۲۹. The growth rings on the scale were employed for age determination in this study. Both sexes exhibited only four age groups (۰+ to ۳+), with the ۲+ age group dominating the population. Females consistently displayed larger sizes compared to males. The von Bertalanffy growth function yielded L t =۱۲۳.۹۰ (۱- e -۰.۲۵(t+۰.۸۷) )  and L t =۱۲۸.۱۰ ۱- e -۰.۲۹ t+۰.۶۹  for males and females, respectively. Furthermore, the Fulton condition factor value was significantly higher in females than males. Notably, the maximum gonadosomatic index for both males and females coincided with the spawning seasons (May to August). Absolute fecundity varied from ۲۹۰ to ۱۷۱۰ oocytes, with a mean of ۷۹۳ oocytes. This study presents comprehensive data on the biological characteristics of the South Caspian Spirlin, providing valuable insights for fish stock assessment studies.

کلیدواژه ها:

Population parameters ، Fecundity ، Age determination ، Gonadosomatic index