The Effects of Mucilage Event on the Population of Critically Endangered Pinna nobilis (Linnaeus 1758) in Ocaklar Bay (Marmara Sea, Turkey)

Abstract

This paper aimed to understand the potential effects of the mucilage event on the critically endangered Pinna nobilis in Ocaklar Bay located at the southern Marmara Sea. Underwater surveys were carried out in October 2020 and July 2021. The study area covers 500 that was divided into 5 main zones having 100 areas (10×10 m). Then, each main zone was separated into sub areas covering 25 (5×5 m). The habitat structure, depth, and availability of the mucilage event were observed by SCUBA diving equipment in sub areas. During the underwater observations, the total number of dead and alive individuals was counted as 228 of which 130 individuals were alive and 98 were dead. The minimum and maximum population density (including both dead and alive individuals) of P. nobilis was found to be between 10 individuals per 100 and 112 individuals per 100 in the study area, respectively. The mortality rates were calculated as 35.96% and 16.12% for the years 2020 and 2021, respectively. This paper puts forward that the P. nobilis population could be resistant to extreme environmental stress and even juvenile individuals (smaller than 15 cm) were recruited in the study area during the mucilage event.