Population structure of the bivalve Mytilaster lineatus (Gmelin, 1791) in the artificial constructions of ports in the southwestern of Caspian Sea

Rocky shores or artificial structures increase the diversity of sessile and mobile fauna. On the Southern shores of the Caspian Sea, these areas have been constructed artificially. The bivalve Mytilaster lineatus is one of the non-native species of the Caspian Sea, which widely distributed in the southern coasts. In this investigation, a certain level of the breakwater walls in in both regions of the Anzali port and the Caspian port were scraped and cleaned off all organisms. The population structure, growth, and abundance of M. lineatus were seasonally investigated in the sampling units. M. lineatus species was not present inside the port area of Anzali region, while it was established in the marina area of the Caspian port but its abundance was gradually decreased. A gradually increase in the abundance and biomass of the bivalves was observed in both marine parts of the mentioned regions. Five months after the beginning of survey, all length classes were observed in the population after five months and the height length of 13 mm present in the specimens. One year after the first sampling, the maximum length was 17.13 mm. The growth rate in summer-autumn was calculated at about 0.075 mm per day. After one year, the biomass was about 2 kg per square meter, which shows that this species is extremely invasive in the southern Caspian regions. The abundance of this species in areas far from the coast can provide the food resources for many species such as sturgeon fish and Kutum, which can be investigated by a pilot program with creating artificial habitats.