Management of Caspian Roach Rutilus caspicus (Yakovlev, 1870) fishing using fish-length based indicators in the southeast coast of the Caspian Sea

In the current study, to obtain length indices for the sustainable fishing management of Caspian roach, the LBB (Length-Based Bayesian Biomass Estimator) model, which is a new and powerful but simple solution based only on the length data, was used. Three important management indicators including length at the first catch (Lc), optimum length at the first capture (Lc-opt), and optimal length of capture (Lopt) were estimated, and their values were 17.7, 21 and 24 cm, respectively. The values of Lmean/Lopt and Lmean/LF=M ratios were almost smaller than 1, which indicated the optimal yield is not performed. In this study, Lc/Lc-opt ratio was less than 1 and Lmax5%/Linf or L95%/Linf indice was smaller than 0.8 and the number of megaspawners less than 1% and the percentages of specimens at the optimum size of less than 10% were estimated. These findings indicated the absence or presence of a few old and large fish in the stock, and the broodstock population has been reduced to a level where it no longer has the reproductive capacity to revive itself. Caspian Roach was preserved to a great extent based on  = 14 cm due to a very low percentage of immature fish (less than 5%) in the catch and L25%/L50>0.3, Lmean/L50>1, and Lc/L50>1. According to the findings of this research, including the optimal length of capture in the management procedures will probably have a better relative performance for the conservation and sustainable exploitation of Caspian Roach.