A recent occurrence signal of Chrysaora hysoscella in the northern Aegean Sea and Sea of Marmara: Evidence from citizen science and field observations

A recent occurrence signal of Chrysaora hysoscella in the northern Aegean Sea and Sea of Marmara: Evidence from citizen science and field observations

İlayda Destan Öztürk

ORCID ID: 0000-0001-8915-6236

Department of Physical Oceanography and Marine Biology, Institute of Marine Sciences and Management, İstanbul University, İstanbul, TÜRKİYE
Turkish Marine Research Foundation (TUDAV), P.O. Box: 10, Beykoz, Istanbul, TÜRKİYE

Abstract

Citizen science provides a valuable complementary approach for documenting jellyfish occurrence across broad spatial scales. This study examined recent records of the compass jellyfish Chrysaora hysoscella along Türkiye’s coastal waters using photographically verified observations submitted to the platform “YaYakarsa?” (National Jellyfish Monitoring Program) between April and June 2026, together with a targeted shoreline field survey. A total of 29 verified records were documented, with observations concentrated in the northeastern Aegean Sea and the Sea of Marmara. Most records originated from coastal waters (20 of 29), while stranded and offshore observations were less frequent. Reported encounter magnitude was generally low, with 21 records involving fewer than 10 individuals, seven involving 10-100 individuals, and one involving 100-500 individuals. Swimming and coastal walking were the most frequently reported observer activities, highlighting the influence of coastal accessibility and observer effort on the spatial pattern of citizen science records. A targeted shoreline survey conducted at Yıldız Bay, Gökçeada, on 28 May 2026, documented 98 stranded C. hysoscella individuals along an approximately 100m shoreline, providing complementary field-based documentation of a localized stranding event. The findings highlight the complementary roles of photographically validated citizen science observations and targeted field surveys in documenting the spatial occurrence of jellyfish and providing detailed evidence of localized stranding events.

Keywords: Scyphozoa, Pelagiidae, jellyfish monitoring, coastal stranding, gelatinous zooplankton, Eastern Mediterranean

Pages: 115-132

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