Hotspots and lost stocks: Critical analysis of Atrina fragilis (Pennant, 1777) population in the Sea of Marmara

Orhun Hisli, Senem Çağlar

ORCID IDs: O.H. 0000- 0002-9102-4125; S.Ç. 0000-0001-5882-9020

Institute of Graduate Studies in Sciences, İstanbul University, 34116, Fatih, İstanbul, TÜRKİYE
Department of Biology, Faculty of Science, İstanbul University, 34134, Vezneciler, İstanbul, TÜRKİYE

Abstract

Atrina fragilis, a large bivalve mollusc acting as an “ecosystem engineer” by providing hard substrate on the seabed, is under serious threat in the Mediterranean basin, particularly due to bottom trawl fisheries. This study was conducted in October 2023 to determine the distribution, population density, and morphometric characteristics of A. fragilis populations in the Sea of Marmara. Field surveys comprised bottom trawl operations carried out at nine stations within a depth range of 26.7 m to 115 m. It was determined that the population density of the species exhibited distinct variation among regions. The maximum individual density was recorded in the Ergene Basin (ST-8) with 3172 individuals/km², followed by Marmara Ereğlisi (ST-9) with 1034 individuals/km². Shell lengths of the examined individuals (N=65, 60 live, 5 dead) ranged between 10.2 cm and 30.3 cm. The findings revealed that A. fragilis forms viable populations in the mesophotic zone of the Sea of Marmara; however, its distribution is patchy and sparse in areas subject to intense fishing pressure. These results highlight the necessity of mapping sensitive habitats where the species is densely present and developing conservation strategies within fisheries management plans.

Keywords: Atrina fragilis, population density, bottom trawl, benthic ecology, Sea of Marmara

Pages: 44-62

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