Distribution and some bio-ecological characteristics of a new invasive pacific oyster (crasostrea gigas) in the eastern black sea region

The Pacific oyster Crassostrea gigas is a bivalve species native to the Pacific Ocean with significant commercial value. It is cultivated in many parts of the world and is the most widely produced bivalve species globally. Due to its high adaptability to changing environmental conditions, rapid growth ability, and strong reproductive potential, this invasive species has a wide range of distribution. In this thesis study, the presence of C. gigas in the Eastern Black Sea region was investigated using SCUBA and ABC diving methods, and sampling was carried out in areas where the species was found. The distributions, densities, morphometric characteristics, and nutrient compositions were analyzed for C. gigas. During the study period, 673 individuals were sampled. Measurements of shell length (SL), shell width (SW), shell thickness (ST), shell weight (SHW), total weight (TW), and meat weight (MW) were taken for the sampled individuals. It was found that shell lengths varied between 11.87 mm and 157 mm. The relationship between shell length and weight was calculated as W = 0.0021SL2.4039, indicating negative allometric growth. The biomass of the species in the sampled regions Fatsa, Giresun, and Ünye was calculated as 0.7, 0.3, and 0.5 kg/m², respectively, and the density as 6.9, 5.5, and 5.2 N/m², respectively. The nutritional composition of the species was found to be 13.64% protein, 7.46% lipid, 76.96% moisture, and 1.94% ash. In conclusion, it is assessed that the species has started to intensely invade the Turkish coasts of the Black Sea and is able to adapt and reproduce in the region. Therefore, it is of great importance to study how this species will spread in the Black Sea in the near future, as well as its potential for expansion and its impact on the ecosystem. If the species successfully adapts and harmoniously integrates into the ecosystem, it is projected to contribute significantly to the fishing economy in the Black Sea.