Models for length back-calculation in Caspian Kutum, Rutilus kutum (Pisces: Cyprinidae) from the Caspian Sea

The Caspian Kutum, Rutilus Kutum (Kamensky 1901) specimens were sampled by purse seine in the northern Iranian coast of the Caspian Sea at four locations:  Feridoonkenar Shahed, Mahmoudabad Khoram, Lariim Azadi fishing coop, and the Shiroud River in Ramsar city. “Back-calculation” is a retrospective method of estimating the characteristics of growth of fish in terms of length and rate of growth in the years preceding capture. Back-calculation of fish lengths at previous ages from scales or otoliths is a widely used approach to estimate both individual and population growth history. The back-calculated lengths of the Caspian kutum,Rutilus kutum (Kamensky 1901) were obtained  using six different  models, namely  scale  proportional  hypothesis,  body proportional  hypothesis,  Fraser  Lee,  nonlinear  scale  proportional  hypothesis,  nonlinear body proportional hypothesis, and the newest method, Morita Matsuishi model. The results showed that the preferred back-calculation models is Fraser Lee model  for both  males  and  females,  while  the  nonlinear  body proportional hypothesis is only for  the  females.