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A Multi-Scale Assessment of Estuarine Fish Communities in Irrawaddy Delta

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A Multi-Scale Assessment of Estuarine Fish Communities in Irrawaddy Delta

Ko Ko Tun Thwin 1,2,3,4,5 Thiri Htet 6 Caixin Liu 1,2,3,5 Htet Naing Nay 2 Tao Qin 1,2,3,5 Htet Zaw Phyo 2 Jiang Bai 1,2,3,5 Jianbing Lyu 1,2,5 Thaung Naing Oo 4 Xiaoyong Chen 1,2,5,*

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1
Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences, Yezin, Naypyitaw 05282, Myanmar
2
Yunnan Key Laboratory of Biodiversity and Ecological Conservation of Gaoligong Mountain, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650201, China
3
University of Chinese Academy of Sciences, Beijing 100190, China
4
Forest Department, Ministry of Natural Resources and Environmental Conservation, Naypyitaw 15011, Myanmar
5
Yunnan International Joint Laboratory of Southeast Asia Biodiversity Conservation, Menglun 666303, China
6
Independent Researcher, Naypyitaw 15011, Myanmar
*
Authors to whom correspondence should be addressed.

Received: 13 May 2026 Revised: 11 June 2026 Accepted: 24 June 2026 Published: 02 July 2026

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© 2026 The authors. This is an open access article under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).

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Ecol. Divers. 2026, 3(3), 10009; DOI: 10.70322/ecoldivers.2026.10009
ABSTRACT: This study quantitatively analyzes fish community responses to environmental gradients in Myanmar’s Irrawaddy Delta. Integrating beta-diversity partitioning, Threshold Indicator Taxa Analysis (TITAN), single-season occupancy modeling, and Structural Equation Modeling (SEM), and species co-occurrence network analysis, we identified primary environmental filters shaping ichthyofaunal structure. Spatial comparison between Bogale and Pyapon ecosystems revealed fundamentally distinct communities driven predominantly by species turnover (87.1%). Network topologies further demonstrated a significant spatial restructuring of biological interactions, with the primary network hub role shifting from the highly sensitive Tenualosa ilisha in the upper estuary to the highly adaptable Macrognathus zebrinus in the lower delta. Furthermore, SEM established a substantial structural connection between environmental stress and biological assemblage response (β = 0.99), suggesting water quality as the ecosystem’s master driver. TITAN and occupancy models demonstrated an “estuarine enrichment” effect, where primary network hubs (Tenualosa ilisha, Coilia neglecta) reached peak occupancies only beyond high salinity thresholds (>18.16 ppt). However, escalating water temperatures act as a critical limiting factor, with a strict thermal boundary identified at 27.6 °C, beyond which sensitive taxa populations rapidly decline. These findings provide direct implications for adaptive fisheries management, underscoring the necessity of monitoring osmotic and thermal change-points to protect vital fisheries from compounded climate change impacts.
Keywords: Irrawaddy Delta; Ecological thresholds; Habitat squeeze; Salinity intrusion; Species turnover
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