Aerial photogrammetric monitoring on spawning migration of pink salmon Oncorhynchus gorbusha using consumer–class UAVs applied to topographic conditions of the rivers in Sakhalin

Methodology for the aerial photogrammetric counting of pacific salmon spawners with serial unmanned aerial vehicles (UAVs) is developed and tested for the rivers of southeastern Sakhalin on example of pink salmon Oncorhynchus gorbuscha. In total, 22 water streams with the total length of about 230 km were surveyed during the spawning migrations in July-August of 2022–2024. Traditional methods of the counting are labor-intensive and ineffective in this area because of hard relief and high afforestation of the river shores, but operational monitoring with consumer-class UAVs (DJI Phantom 4 Pro V2.0, DJI Mini 2, DJI Matrice 300 RTK) is available. The optimal parameters for aerial survey have been established: the flight altitude 20–100 m, UAV speed up to 6 m/s, longitudinal overlap of the images ≥ 80 % and the transverse overlap ≥ 40 %. The materials of 88 flight missions are processed in Agisoft Metashape Professional software package and orthophotoplans with resolution of 1.0–1.5 cm/pixel are obtained, suitable for visual identification and counting of fish using the geoinformation system NextGIS QGIS. Effectiveness of different UAV models is compared. The main limitations of the method concerned to weather conditions and the riverbed cover are defined. The developed methodology is an effective and economically feasible tool for operational control of spawning that can be used for the fishery regulation and evaluation of reproduction efficiency for pacific salmon in the Sakhalin Region.

1. Dulenin, A.A., Dulenina, P.A., Kotsyuk, D.V., and Sviridov, V.V., Experience and perspectives of small unmanned aerial vehicles application for marine coastal biological studies, Tr. Vses. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr., 2021, vol. 185, pp. 134–151. doi 10.36038/2307-3497- 2021-185-134-151

2. Zaporozhets, O.M. and Zaporozhets, G.V., Using the photo- and video records for assessment of pacific salmon escapement on migration routes and spawning grounds: some of methodical approaches, Issled. Vodn. Biol. Resur. Kamchatki Sev.-Zapadn. Chasti Tikhogo Okeana, 2017, no. 47, pp. 77–90.

3. Zaporozhets, O.M., Zaporozhets, G.V., and Feldman, M.G., Estimation of the number of sockeye salmon adults and their distribution by spawning stations in the basin of Lake Nachikinskoye (Kamchatka) in 2019, Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr., 2020, vol. 200, no. 3, pp. 618–634. doi 10.26428/1606-9919-2020-200-618-634

4. Kolpakov, N.V., Makoedov, A.A., Nikitin, V.D., Maznikova, O.A., Ignatiev, Y.I., and Antonov, A.A., Results of pacific salmon fishery in the Sakhalin-Kuril Region in 2024, in Bulletin on the study of Pacific salmon in the Far East, Vladivostok: TINRO, 2025, no. 19, pp. 19–36. doi 10.26428/ losos_bull19-2025-19-36. EDN: CFTFTI.

5. Kotsyuk, D.V., Sviridov, V.V., and Povarov, A.Yu., Experience of implementation and approaches for further automation in unmanned aerial counting of pacific salmon in the Okhotsk district of Khabarovsk Region, Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr., 2024, vol. 204, no. 3, pp. 705–721. doi 10.26428/1606-9919-2024-204-705-721. EDN: SJRXIS.

6. Makoedov, A.A., Dynamics of the formation of Pacific salmon of Russian origin in the Far Eastern fishery basin, in Mater. 4-y nauchn. shkoly-konf. mol. uchenykh i spetsialistov “Sovremennyye aspekty rybokhozyaystvennoy nauki i genomnyye tekhnologii v akvakul’ture i rybolovstve” (Proc. 4th Sci. Entific. Schools Pier. Scientists and Specialists “Modern aspects of fisheries science and genomic technologies in aquaculture and fisheries”), Sytova, M.V., Muge, N.S., Gordeev, I.I., eds, Moscow: VNIRO, 2023, pp. 54.

7. Makoedov, A.A. Access to aquatic biological resources in the Sakhalin-Kuril region, Theses of reports from the International Scientific and Practical Seminar “Pacific Salmon in the World of Human Relations: Economic, Social, Environmental, Historical, Ethnic, and Cultural Aspects”, Petropavlovsk-Kamchatsky: Kamchatpress, 2019, pp. 74−76.

8. Makoedov, A.A., Kolpakov, N.V., Nikitin, V.D., Zhivoglyadov, A.A., Ignatiev, Y.I., and Antonov, A.A., Results of economic usage of the pacific salmon resources in the Sakhalin-Kuril region in 2023, in Bulletin on the study of Pacific salmon in the Far East, Vladivostok: TINRO, 2024, no. 18, pp. 49–66. doi 10.26428/losos_bull18-2024-49-66. EDN: CIBDPD.

9. Makoedov, A.A., Nikitin, V.D., Zhivoglyadov, A.A., Ignatiev, Y.I., and Antonov, A.A., Results of the pacific salmon fishery in the Sakhalin-Kuril region in 2022, in Byulleten’ no. 17 izucheniya tikhookeanskikh lososei na Dal’nem Vostoke (Bulletin No. 17 for the Study of Pacific Salmon in the Far East), Vladivostok: TINRO, 2023, pp. 57–68. DOI: 10.26428/losos_bull17-2023-57-68. EDN: SHCHSW.

10. Makoedov, A.A., Nikitin, V.D., Ignatiev, Yu.I., Antonov, A.A., and Kovtun, M.V., Results of the pink salmon and chum salmon fishery in the Sakhalin-Kuril region in 2019, in Byull. N 14 izucheniya tikhookeanskikh lososei na Dal’nem Vostoke (Bull. No. 14 Study of Pacific Salmon in the Far East), Vladivostok: TINRO-Tsentr, 2019, pp. 65–75.

11. Makoedov, A.N. and Makoedov, A.A., Population dynamics and catch prospects of russian pacific salmon (Ohcorhynchus, Salmonidae), Vestn. Kamchatskogo Gos. Tekh. Univ., 2022, no. 60, pp. 84–97. doi 10.17217/2079-0333-2022-60-84-97

12. Makoedov, A.N. and Makoedov, A.A., Pacific salmon: the status of stocks and prospects for the fishery, Russ. J. Mar. Biol., 2022, vol. 48, no. 7, pp. 547–554. doi 10.1134/s1063074022070112

13. Makoyedov, A.N. and Makoyedov, A.A., Use of Pacific salmon stocks in the Sakhalin region, in Mater. 6 naucho-prakt. konf. molodykh uchenykh s mezhdunar. uchastiyem “Sovremennyye problemy i perspektivy razvitiya rybokhozyaystvennogo kompleksa” (Proc. 6th Sci.-Pract. Conf. Young Sci. Int. Participation “Modern problems and prospects for the development of the fishery complex”), Moscow: VNIRO, 2018, pp. 163–167.

14. Nikiforov, A.I., Gordeev, I.I., and Ridiger, A.V., Monitoring survey on run of spawners of pink salmon Oncorhynchus gorbuscha by means of UAV in the spawning rivers of Sakhalin Island in 2022, in Bull. N 17 izucheniya tikhookeanskikh lososei na Dal’nem Vostoke (Bull. No. 17 Study of Pacific Salmon in the Far East), Vladivostok: TINRO, 2023, pp. 115–121. doi 10.26428/losos_bull17-2023-115-121. EDN: TEKRFK.

15. Sviridov, V.V., Kotsyuk, D.V., and Podorozhnyuk, E.V., Photogrammetric counts of pacific salmon using consumer-grade unmanned aerial vehicles, Russ. J. Mar. Biol., 2022, vol. 48, no. 7, pp. 587–600. doi 10.1134/s1063074022070136

16. Sviridov, V.V., Podorozhnyuk, E.V., Nikitin, V.D., and Skorik, A.V., Modifications of unmanned aerial survey on spawners of pacific salmons in the rivers of Sakhalin and Khabarovsk Regions, Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr., 2022, vol. 202, no. 4, pp. 1015–1031. doi 10.26428/1606-9919-2022-202-1015-1031. EDN: JULFRV.

17. Sviridov, V.V. and Povarov, A.Yu., Application of artificial intelligence methods to automate post-spawn chum salmon individuals enumeration by means of unmanned aerial vehicles in Khabarovsk Territory, Vopr. Rybolov., 2024, vol. 25, no. 4, pp. 113–124. doi 10.36038/0234-2774-2024-25-4-113-124

18. Sviridov, V.V., Povarov, A.Yu., and Kotsyuk, D.V., Automation of unmanned counting for spawners of chum and coho salmon with methods of artificial intelligence, Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr., 2025, vol. 205, no. 3, pp. 518–534. doi 10.26428/1606-9919-2025-205-518-534. EDN: JCTWNA.

19. Fadeev, E.S., Shevlyakov, E.A., and Feldman, M.G., Integrated Monitoring of Escapement of Pacific Salmon Spawners to the Kamchatka River in Real-Time Mode, Russ. J. Mar. Biol., 2019, vol. 45, no. 7, pp. 546–559. doi 10.1134/S1063074019070022

20. Groves, P.A., Alcorn, B., Wiest, M.M., Maselkobc, J.M., and Connor, W.P., Testing unmanned aircraft systems for salmon spawning surveys, Facets, 2016, vol. 1, pp. 187–204. doi 10.1139/facets-2016-0019

21. Harris, J.M., Nelson, J.A., Rieucau, G., and Broussard, W.P., Use of unmanned aircraft systems in fishery science, Trans. Am. Fish. Soc., 2019, vol. 148, no. 4, pp. 687–697. doi 10.1002/tafs.10168

22. Harrison, L.R., Legleiter, C.J., Overstreet, B.T., Bell, T.W., and Hannon, J., Assessing the potential for spectrally based remote sensing of salmon spawning locations, River Res. Applic., 2020, vol. 36, no. 8, pp. 1618–1632. doi 10.1002/rra.3690

23. Kudo, H., Koshino, Y., Eto, A., Ichimura, M., and Kaeriyama, M., Cost-effective accurate estimates of adult chum salmon, Oncorhynchus keta, abundance in a Japanese river using a radiocontrolled helicopter, Fish. Res., 2012, vol. 119–120, pp. 94–98. doi 10.1016/j.fishres.2011.12.010

24. Ponsioen, L., Kapralova, K., Holm, F., Martínez, S.G., and Hennig, B.D., Monitoring fish spawning sites in freshwater ecosystems using low-cost UAV data: A case study of salmonids in lakes in Iceland, bioRxiv, 2021, pp. 1–22. doi 10.1101/2021.06.12.448199

25. Roncoroni, M. and Lane, S.N., A framework for using small Unmanned Aircraft Systems (sUASs) and SfM photogrammetry to detect salmonid redds, Ecological Informatics, 2019, vol. 53, 100976. doi 10.1016/j.ecoinf.2019.100976