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

Çanakkale Boğazı’nda Pinna nobilis (Linnaeus, 1758) Popülasyonunda Ölüm Oranlarının Tespiti

Abstract

Ekolojik anlamda önemli olan Akdeniz’in en büyük çift kabuklu türü Pinna nobilis (Linneaus, 1758)‘in nesli, antropojenik etkilerin yanında 2016 yılından bu yana Haplosprodium pinnae isimli parazitin salgın etkisiyle ciddi tehdit altındadır. Ayrıca, son yıllarda Kuzey Ege Denizi’nde Pinna nobilis popülasyonlarının ölümlerine Haplosprodium pinnae’ nın yanında çoklu enfekte olarak Vibrio sp. gibi türlerin de neden olduğu bildirilmektedir. Bu çalışmada, Pinna nobilis’ in 2016 yılından bu yana Batı Akdeniz’den Doğu Akdeniz kıyılarına hızla yayılmış olan kitlesel ölümlerinin Çanakkale Boğazı’ ndaki Pinna nobilis yataklarındaki etkisini belirlemek amaçlanmıştır. Haziran 2020 ve Eylül 2021 ayları arasında belirlenen 30 örnekleme istasyonunda su altı görsel sayım metodu (hat-çizgi sayımı) ile ikişer kez dalarak, pinaların sayımı yapılmıştır. Su altı gözlemleri için bölgenin su altı karakteristiğine göre tüplü dalış veya serbest dalış yöntemleri gerçekleştirilmiştir. Toplam 2183 dakikalık su altı dip gözlem verilerine göre pinaların ölüm oranı 2020-2021 arasında % 81,15’ den % 94,67’ ye yükselmiştir. Yaklaşık bir yıl sonra pinaların ölüm oranının %100 olduğu istasyonların sayısı 11’ den 14’ e yükselirken, hiç pina görülmeyen istasyonların sayısı 3’ ten 5’ e yükselmiştir. Örnekleme istasyonlarındaki canlı pina sayısının bir sene içerisinde 1108’ den 207’ ye ve toplam yoğunluğun (birey/100m2) 13,15’ ten 9,2’ ye gerilemesi, Pinna nobilis neslinin tükenme tehlikesinin devam ettiğini göstermiştir. Pinna nobilis neslinin tükenme tehlikesinden kurtulabilmesi için biyolojik çalışmaların yanında yetiştiricilik ve transplantasyon çalışmaları yaygınlaştırılabilir.

Keywords

• Pinna nobilis
• Çanakkale Boğazı
• Kitlesel Ölüm
• Hat-çizgi sayımı

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