Determination of Mortality Rates in Pinna nobilis (Linnaeus, 1758) Population in The Çanakkale Strait

Abstract

The population of ecologically important Pinna nobilis (Linneaus, 1758), the largest bivalve species of the Mediterranean, has been under serious threat since 2016 as a result of both anthropogenic effects and the epidemic caused by Haplosporidium pinnae. In addition, in recent years P. nobilis mortalities caused by Vibrio sp. infections in the North Aegean Sea have been reported. In this study, the effects of the mass mortalities of P. nobilis observed in the Mediterranean were investigated in the populations in the Dardanelles. For this purpose, P. nobilis populations in 30 different stations were observed and counted along transects between June 2020 and September 2021. Underwater observations were carried out either by scuba diving or free diving depending on the underwater characteristics of the region. Observations based on a total of 2183 minutes of bottom time indicated that mortality rate of pen shells increased to 94.67% in 2021 as compared to 81.15% in 2021. In addition, in a period 1 year, the number of stations with 100% mortality increased from 11 to 14 and the number of stations with no presence of pen shells increased from 3 to 5. The decrease in the total number of live pen shells from 1108 to 207 and the consequent reduction of pen shell density (individual/100 m2) from 13.15 to 9.2 in a period of one year indicate the imminent threat of extinction for P. nobilis in this region. In addition to monitoring studies, aquaculture of pen shells and their transplantation to affected areas should be carried out to mitigate the effects of mass mortalities observed in this region.

Keywords

• pinna nobilis
• çanakkale strait
• mass mortality
• line transect