pesd2025191001

	PRESENT ENVIRONMENT AND SUSTAINABLE DEVELOPMENT Volume 20, Issue no.1/ 2026

	Title: Mapping Sturgeon Habitats: High-Resolution Riverbed Classification on the Danube River
	Authors : Cristian TRIFANOV 1 , Marian MIERLA 1* , Ion GRIGORAS 1 , Alexandru DOROSENCU 1 , Marian IANI 1 , Marian PARASCHIV 1 , Stefan HONT 1 , Cristian Constantin STOLERIU 2 , Alin MIHU-PINTILIE 3 , Iuliana Mihaela TUDOR 1 , Marian TUDOR 1 1 “Danube Delta” National Institute for Research and Development, Tulcea, Romania 2 Alexandru Ioan Cuza University of Iasi, Faculty of Geography and Geology, Iasi, Romania 3 Alexandru Ioan Cuza University of Iasi, Interdisciplinary Research Institute, Science Department, Iasi E-mail : * Corresponding author: Marian MIERLA, marian.mierla@ddni.ro
	https://doi.org/10.47743/pesd2026201016
	VIEW FULL TEXT
	Abstract Critically endangered Danube sturgeons rely on specific hydro-geomorphological conditions—such as deep riverbed pools and exposed hard substrates—for spawning, overwintering, and resting. However, continuous high-resolution riverbed maps across the Lower Danube remain scarce. This study provides a high-resolution bathymetric and substrate assessment of three key sturgeon habitats within the Danube Delta Biosphere Reserve: Balteni, Nufaru, and Isaccea (Noviodunum) in the Danube Delta Biosphere Reserve. Using a 500 kHz interferometric bathymetric sonar coupled with RTK-GNSS positioning and ADCP velocity profiling, we generated 1 m resolution Digital Terrain Models (DTMs) and mapped benthic substrates via side-scan sonar backscatter segmentation. Deep scour pools driven by bedrock steps were mapped at Balteni (35 m depth) and Nufaru (30 m depth), both hosting exposed hard-bottom substrates that function primarily as overwintering and resting refugia. In contrast, the Isaccea sector features a 17 m deep pool maintained by high flow turbulence over the submerged masonry of the ancient Roman fortress of Noviodunum, exposing a localized gravel-cobble substrate that acts as an active spawning ground. Our findings demonstrate that critical sturgeon habitats in the Lower Danube are highly localized micro-topographic anomalies, emphasizing the necessity of high-definition hydroacoustic surveys for targeted conservation and environmental impact assessments.

	References Blondel, P. (2009). The Handbook of Side-Scan Sonar. Springer-Verlag, Berlin Heidelberg. https://doi.org/10.1007/978-3-540-49886-5 Blondel, P., & Gomez Sichi, O. (2009). Textural analysis of Multibeam Sonar imagery and determination of seabed natures in Maritime Protected Areas. Applied Acoustics, 70(10), 1288–1297. https://doi.org/10.1016/j.apacoust.2008.07.018 Brown, C. J., Smith, S. J., Lawton, P., & Anderson, J. T. (2011). Benthic habitat mapping: A review of progress towards mapping the continental shelf. Estuarine, Coastal and Shelf Science, 92(3), 502–520. https://doi.org/10.1016/j.ecss.2011.02.008 Collier, J. S., & Brown, C. J. (2005). Correlation of side-scan sonar backscatter with sediment grain size on the inner continental shelf. Sedimentology, 52(4), 793–813. https://doi.org/10.1111/j.1365-3091.2005.00719.x Dunea, D., Bretcan, P., Serban, G., Tanislav, D., ?uchiu, E., & Iordache, S. (2022). Water Temperature Variability in the Lower Danube River. In: Danube River Basin. Springer, Cham, 91–105. DOI: https://doi.org/10.1007/978-3-031-03865-5_5 Friedrich, T., Reinartz, R., & Gessner, J. (2018). Sturgeon conservation in the Danube River Basin: How active habitat management can prevent extinction. Journal of Applied Ichthyology, 34(2), 241–252. https://doi.org/10.1111/jai.13554 Gâstescu, P. (2009). The Danube Delta Biosphere Reserve: Geography, Biodiversity, Protection, Management. Romanian Journal of Geography / Revue Roumaine de Géographie, 53(2), 139–152. http://www.rjgeo.ro/, http://www.rjgeo.ro/issues/revue%20roumaine_53_2/p.%20gastescu.pdf GeoAcoustics. (2020). GeoSwath 4R Operation and Processing Manual. GeoAcoustics Ltd., Great Yarmouth, UK. https://www.researchgate.net/publication/304318119_GeoSwath_Plus_side_scan_data_processing_an_example_from_the_Shallow_Survey_Common_Dataset Gessner, J., Freyhof, J., & Kottelat, M. (2010). Acipenseridae. IUCN Red List of Threatened Species. International Union for Conservation of Nature. https://www.iucnredlist.org Holban, E., Diacu, E., & Matei, M. (2022). Pilot validation system of breeding habitats of sturgeon species. International Journal of Conservation Science, 13(3), 1081–1090. https://www.researchgate.net/publication/363586604_Pilot_Validation_System_of_Breeding_Habitats_of_Sturgeon_Species Hon?, ?., Paraschiv, M., Iani, M., Badilita, A., & Suciu, R. (2022). Preliminary migratory fish habitats assessment along the Danube River sector km 863–375. North-Western Journal of Zoology, 18(1), e221401. https://biozoojournals.ro/nwjz/content/v18n1/nwjz_e221401_Hont.pdf Kynard, B., Suciu, R., & Horgan, M. (2002). Migration and habitat use of sturgeons in the Lower Danube River, Romania. Federal Agency for Nature Conservation (BfN) Skripten, 58, 67–74. https://wwfeu.awsassets.panda.org/downloads/13_2002_migration_and_habitats_of_diadromous_danube_river_sturgeons_in_romania_1998_2000.pdf Lucieer, V., Hill, N. A., Barrett, N. S., & Nichol, S. (2013). To what extent can acoustic nearshore seabed mapping inform eco-hydraulic habitat modeling? Marine Geophysical Research, 34(3), 225–238. https://doi.org/10.1007/s11001-013-9184-4 Lurton, X. (2010). An Introduction to Underwater Acoustics: Principles and Applications (2nd ed.). Springer-Verlag, Berlin. https://doi.org/10.1007/978-3-642-11718-2 McGonigle, C., Brown, C., Quinn, R., & Grabowski, J. (2009). Evaluation of multi-frequency acoustic backscatter data for benthic habitat mapping. Estuarine, Coastal and Shelf Science, 81(2), 227–236. https://doi.org/10.1016/j.ecss.2008.10.016 Mitasova, H., Mitas, L., & Harmon, R. S. (2005). Simultaneous spline approximation and topographic analysis for lidar and bathymetric data. IEEE Geoscience and Remote Sensing Letters, 2(4), 375–379. https://doi.org/10.1109/LGRS.2005.854122 NatureFirst Consortium. (2025). Forensic Intelligence and Remote Sensing Technologies for Biodiversity Preservation: Lower Danube Sturgeon Habitat Assessment Report. EU Horizon Europe Project (Grant Agreement No. 101060954). https://www.naturefirst.info/ Onara, D. F., Suciu, R., Paraschiv, M., & Holostenco, D. (2024). Preliminary data on key habitats of sturgeons in the Danube Delta Biosphere Reserve. ResearchGate Publication, Article 386012518. https://www.researchgate.net/publication/386012518 Reinartz, R. (2002). Sturgeons in the Danube Basin: Status, Conservation Measures and Action Plan for the Management of Danube Sturgeons. International Association for Danube Research (IAD), Vienna. https://www.researchgate.net/publication/265260313_Sturgeon_Conservation_in_the_Danube_River_Basin_How_to_implement_the_Sturgeon_Action_Plan_2005 Suciu, R., Paraschiv, M., & Hon?, ?. (2008). Identification of critical habitats for migratory sturgeons in the Lower Danube River. Danube Parks Scientific Series, 2, 45?52. https://www.incdpm.org/_files/ugd/698962_b592a834336f45158ff25a59b77f660f.pdf Wolter, C., & Sukhodolov, A. (2024). Assessing potential spawning and nursery habitat availability in large regulated rivers for critically endangered sturgeon species. Journal of Applied Ecology. PMC11588678. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11588678/ WWF Danube-Carpathian Programme & Interreg Danube Region. (2026). Mapping Potential Sturgeon Spawning Habitats in the Bulgarian-Romanian Danube (MonStur Project). Interreg Danube Transnational Programme Publications. https://interreg-danube.eu/projects/monstur-in-the-danube/news/mapping-potential-sturgeon-spawning-habitats-in-the-bulgarian-danube

© 2007 Present Environment and Sustainable Development
ISSN 1843-5971 (Printed version) ISSN 2284 – 7820 (online version)

Home Editorial Board

Webdesign Adrian Ursu ©2008 UAIC