Population dynamics, morphometric characteristics and length-weight relationship of Mytilaster lineatus on the southwest coast of the Caspian Sea (Gilan province)

The bivalve Mytilaster lineatus is an invasive species that has been able to stabilize its position after entering the Caspian Sea. The objectives of this study were to investigate population dynamics, dispersion, morphometric characteristics, coverage percentage, frequency and longitudinal weight relationship of this species in the coasts of Guilan province. Seven stations along the coastal strip of Gilan province were selected and sampling from rocky, natural, and man-made beaches on a monthly basis during a year (April2019 to March 2020) was carried out by 15 x15 cadres. The mean and standard deviation of the number of samples in the squares were 324.05 ± 49.86 and the mean weight was 25.65 ± 44.59 and the mean shell length was 11.35± 0.68 mm and there were significant differences between different stations.The principal components test also showed that the salinity and oxygen of the water solution had the highest correlation with the frequency of this species. The maximum longitudinal frequency at 11 mm was also determined. The length-weight relationship of this species had a high correlation (r2 = 95). Comparison of different longitudinal groups showed that the larvae were more present from July to November and the adult group from April to September and a mixture of the two groups was seen from September to March.This longitudinal pattern indicates the reproduction of this species in summer and early autumn months in the southern Caspian basin.