RECENT CHANGES IN THE OKHOTSK SEA ECOSYSTEM (2008–2018)

Recent changes of the main oceanographic, chemical, and biological parameters of the Okhotsk Sea ecosystem are considered briefly for the last decades (2000–2010s), mostly on the data obtained in marine expeditions conducted by Pacific Fish. Res. Center (TINRO) annually. Since the mid-2000s, anomalous oceanographic conditions were formed there with prevailing heightened temperature in all layers of the sea and lowered ice cover caused by changes in the atmosphere circulation with northward shift of cyclones tracks in winter and weakening of winter monsoon. The ice cover was below the normal value every year since 2004. In the warmer winter conditions, producing of the high-density water on the northern shelf decreased from 3.2–7.8 . 103 km3 in 1998–2002 to 1.2 . 103 km3 on average in 2004–2015, and the water with density sq > 26.8 was not formed at all in 2007–2009, 2011, and 2014–2015. As the result, winter convection, including the slope convection, became weaker and shallower and ventilated worse the water column, so dissolved oxygen content decreased in the lower portion of the intermediate layer, usually ventilated by slope convection. For the core of the intermediate layer (isopycnal surface 27.0 σθ), positive trend of temperature is estimated as +0.04…+0.16 o/decade, by areas, while the trend of dissolved oxygen content is negative: –0.07…–0.14 mL/L.decade, by areas. From the other hand, spring phytoplankton bloom became less intensive, presumably because of poorer upward flux of nutrients in conditions of weaker vertical mixing, and zooplankton biomass decreased, particularly for phytophages. However, these changes did not cause significant response in fluctuations of stocks for the main commercial fish and crab species. The largest stock of walleye pollock had cyclic fluctuations driven mostly by intra-population regulations, the stocks of pacific herring were rather stable, and the stocks of deep-water fish species, as flounders and halibuts had a slight tendency to growth, possibly because of better conditions for reproduction. Indeed, the densest aggregations of greenland halibut shifted from the depth of 600–700 m to 500–600 m that may be caused by de-oxygenizing of the lower portion of the intermediate layer. Crabs abundance also had positive dynamics obviously because of the effect of protective measures for red king crab in the 2009–2012, though its biomass continued to grow even after restoring the commercial landings. There is concluded that recent changes in the macroecosystem of the Okhotsk Sea correspond to the conception of the sub-polar ecosystems transformation under climate warming toward decreasing of their productivity and increasing of their functioning efficiency that was proposed earlier for the Japan Sea. Thus, from position of commercial exploitation of marine biological resources, the modern reconstruction of the Okhotsk Sea ecosystem under the climate change impact could be considered as a positive process.

1. Avdeev, G.V. and Ovsyannikov, E.E., Estimation of walleye pollock stock in the northern Okhotsk Sea by results of ichthyoplankton survey in the year 2005, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2006, vol. 145, pp. 120–145.

2. Avdeev, G.V., Smirnov, A.V., and Fronek, S.L., Interannual dynamics of pollock abundance in the northern Okhotsk Sea in 1990s, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2001, vol. 128, no. 1, pp. 207–221.

3. Borets, L.A., Donnye ikhtiotseny rossiiskogo shel’fa dal’nevostochnykh morei: sostav, struktura, elementy funktsionirovaniya i promyslovoye znacheniye (Benthic Ichthyocoenes on the Russian Shelf of the Far Eastern Seas: Composition, Structure, Functioning Elements, and Commercial Significance), Vladivostok: TINRO-Tsentr, 1997.

4. Volvenko, I.V., First experience of using a new database on net zooplankton in the Far-Eastern Seas and adjacent Pacific waters, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2016, vol. 187, pp. 19–47.

5. Volkov, A.F., Seasonal and long-term dynamics of epipelagic plankton in Sakhalin waters, the Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2013а, vol. 174, pp. 170–186.

6. Volkov, A.F., Seasonal and long-term dynamics of epipelagic plankton in Kamchatka waters of the Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2013b, vol. 175, pp. 206–233.

7. Glebova, S.Yu., Cyclones over the Pacific Ocean and Far-Eastern Seas in cold and warm seasons and their influence on wind and thermal regime in the last two decade period, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2018, vol. 193, pp. 153–166.

8. Gorbatenko, K.M., Quantitative distribution and feeding of euphausiids in the Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2016а, vol. 185, pp. 204–214.

9. Gorbatenko, K.M., Distribution, biomass, and year-to-year dynamics of Sagitta in the Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2016b, vol. 184, pp. 168–177.

10. Gorbatenko, K.M., Trophodynamics of aquatic organisms in the Sea of Okhotsk, Extended Abstract of Doctoral (Biol.) Dissertation, Vladivostok: TINRO-Tsentr, 2018.

11. Gorbatenko, K.M., Lazhentsev, A.E., and Kiyashko, S.I., Seasonal dynamics of trophic status for zooplankton in the Okhotsk Sea (on the data of testing the stable isotopes of C and N), Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2014, vol. 177, pp. 25–39.

12. Dulepova, E.Р., Utilization of forage resources by nekton in periods of its high abundance in the Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2013, vol. 173, pp. 146–163.

13. Dyakov, Yu.P., Kambaloobraznye (Pleuronectiformes) dal’nevostochnykh morei Rossii (Flatfish (Pleuronectiformes) of the Far Eastern Seas of Russia), Petropavlovsk-Kamchatsky: KamchatNIRO, 2011.

14. Zavernin, J.P., The effect of the hydrometheorological conditions on the time of shore approaching for spawning and on the generation quantity of the Okhotsk herring, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 1972, vol. 81, pp. 44–51.

15. Zolotov, A.O., Terentiev, D.A., Novikova, O.V., and Il’in O.I., Long-term dynamics of demersal fish biomass on the shelf of West Kamchatka, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2013, vol. 173, pp. 30–45.

16. Zuenko, Yu.I., Impact of climate change on the key elements of the Sea of Japan ecosystem, Extended Abstract of Doctoral (Geogr.) Dissertation, Vladivostok: TINRO-Tsentr, 2009.

17. Zuenko, Yu.I. and Nuzhdin, V.A., Impact of modern changes of oceanographic conditions in the Sea of Japan on state of the Primorye pollock population, Vopr. Rybolov., 2018, vol. 19, no. 3, pp. 377–386.

18. Zuenko, Yu.I., Figurkin, A.L., and Matveev, V.I., Recent changes in producing of the Intermediate water in the Okhotsk Sea and its properties, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2018, vol. 193, pp. 190–210.

19. Il’inskii, O.K., The summer Far Eastern low-pressure area, Tr. Dal’nevost. Nauchno-Issled. Gidrometeorol. Inst., 1960, vol. 11, pp. 3–53.

20. Il’inskii, O.K., The Okhotsk anticyclone, Tr. Dal’nevost. Nauchno-Issled. Gidrometeorol. Inst., 1959, vol. 7, pp. 10–32.

21. Cushing, D.H., Marine Ecology and Fisheries, Cambridge: Cambridge Univ. Press, 1975.

22. Shuntov, V.P., Bocharov, L.N., Volvenko, I.V., and Kulik, V.V., Makrofauna pelagiali Okhotskogo morya: tablitsy vstrechaemosti, chislennosti i biomassy. 1984–2009 (Pelagic Macrofauna of the Okhotsk Sea: Occurrence, Abundance, and Biomass. 1984–2009), Shuntov, V.P. and Bocharov, L.N., Eds., Vladivostok: TINRO-Tsentr, 2012.

23. Matveev, V.I. and Figurkin, A.L., Interannual changes in dissolved oxygen and temperature intermediate waters deep Sea of Okhotsk, in Mater. 16 konf. po promyslovoi okeanologii (Proc. XVI Conf. on Fishery Oceanology), Kaliningrad: AtlantNIRO, 2014, pp. 96–97.

24. Moiseev, P.A., Cod and flounders of the Far Eastern seas, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 1953, vol. 40.

25. Muktepavel, L.S., Spatio-temporal variations of coastal polynyas in the main spawning grounds of Okhotsk herring, Vopr. Promysl. Okeanol., 2007, vol. 3, pp. 314–332.

26. Muktepavel, L.S. and Shatilina, T.A., Some patterns of formation of extremely low-ice winters in the Sea of Okhotsk, Sovrem. Probl. Distantsionnogo Zondirovaniya Zemli Kosmosa, 2009, vol. 6, no. 1, pp. 429–441.

27. Naumenko, N.I., Biologiya i promysel morskikh sel’dei Dal’nego Vostoka (Biology and Harvesting of Sea Herring in the Far East), Petropavlovsk-Kamchatsky: Kamchatsky Pechatny Dvor, 2001.

28. Nikolsky, G.V., Teoriya dinamiki stada ryb (The Theory of Fish Stock Dynamics), Moscow: Pishchevaya Promyshlennost’, 1974.

29. Ovsyannikov, E.E., Walleye pollock year classes abundance assessment in the northern Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2009, vol. 157, pp. 64–80.

30. Ovsyannikov, E.E., Ovsyannikova, S.L., and Sheybak, A.Yu., Dynamics and structure of walleye pollock stock in the northern Okhotsk Sea in the 2000s, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2013, vol. 172, pp. 133–148.

31. Pogosyan, Kh.P., Seasonal fluctuations of the general atmospheric circulation, Tr. Tsentr. Inst. Prognozov, Leningrad: Gidrometeoizdat, 1947, vol. 1, no. 28.

32. Smirnov, A.V., Effects of some physical and biological factors on the Okhotsk Sea pollock eggs, larvae, and juveniles survival, Vopr. Rybolov., 2005, vol. 6, no. 2(22), pp. 278–297.

33. Smirnov, A.V. and Avdeev, G.V., Dynamics of age-size structure and formation of commercial stock of walleye pollock in the Okhotsk Sea in late 1990-s — early 2000-s, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2003, vol. 135, pp. 94–112.

34. Tuponogov, V.N. and Kodolov, A.S., Polevoi opredelitel’ promyslovykh i massovykh vidov ryb dal’nevostochnykh morei Rossii (A Field Key to Commercial and Common Fish Species from the Far Eastern Seas of Russia), Vladivostok: Russky Ostrov, 2014.

35. Turnin, B.V., The spawning range of the Okhotsk herring, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 1973, vol. 86, pp. 12–21.

36. Fadeev, N.S., Harvesting and status of walleye pollock stocks, in Biologicheskiye resursy shel’fovykh i okrainnykh morei (Biological Resources of Shelf and Marginal Seas), Moscow: Nauka, 1990, pp. 99–111.

37. Fadeev, N.S. and Wespestad, V., Review of walleye pollock fishery, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2001, vol. 128, pp. 75–91.

38. Figurkin, A.L., Variability of temperature and salinity for bottom waters in the northern Okhotsk Sea, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2011, vol. 166, pp. 255–274.

39. Tskhai, Zh.R., Spatial-temporal variability of chlorophyll-a concentration in the surface layer of the Sea of Okhotsk and adjacent waters as inferred from satellite data, Cand. Sci. (Geogr.) Dissertation, Moscow: Inst. Okeanol. im. P.P. Shirshova, Ross. Akad. Nauk, 2017.

40. Shatilina, T.A. and Anzhina, G.I., Change of the Asian and Far Eastern depressions parameters in the second half of 20th century, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2006, vol. 144, pp. 300–311.

41. Shuntov, V.P., Biologiya dal’nevostochnykh morei Rossii (Biology of the Far Eastern Seas of Russia), Vladivostok: TINRO-Tsentr, 2016, vol. 2.

42. Shuntov, V.P. and Volvenko, I.V., Supplements to quantitative assessments of zooplankton in the Far Eastern seas and adjacent waters of the North Pacific, Izv. Tikhookean. Nauchno–Issled. Inst. Rybn. Khoz. Okeanogr., 2017, vol. 191, pp. 130–146.

43. Shuntov, V.P., Dulepova, E.P., Temnykh, O.S., Volkov, A.F., Naidenko, S.V., Chuchukalo, V.I., and Volvenko, I.V., The status of biological resources in connection with dynamics of macroecosystems in the Far Eastern economic zone of Russia, in Dinamika morskikh ekosistem i sovremennye problemy sokhraneniya bioresursnogo potentsiala morei Rossii (Dynamics of Marine Ecosystems and the Current Problems of Conservation of the Bioresource Potential of the Russian Seas), Vladivostok: Dal’nauka, 2007, pp. 75–176.

44. Figurkin, A.L., The volumes of Dense Shelf Water in the northern part of the Okhotsk Sea in April-May 1994–2015, Proc. 31st Int. Symp. on Okhotsk Sea & Sea Ice, Mombetsu, Hokkaido, 2016, pp. 311–313.

45. Melnikov, I.V. and Loboda, S.V., Interannual variation of the pacific herring stocks in the Okhotsk Sea in connection with the last years cooling, PICES Sci. Rep., 2004, no. 26, pp. 127–131.

46. Boyer, T.P., Antonov, J.I., Baranova, O.K., Coleman, C., Garcia, H.E., Grodsky, A., Johnson, D.R., Locarnini, R.A., Mishonov, A.V., O’Brien, T.D., Paver, C.R., Reagan, J.R., Seidov, D., Smolyar, I.V., and Zweng, M.M., World Ocean Database 2013 Version 2, NOAA Atlas NESDIS 72, Levitus, S., Ed., Silver Spring, MD: NOAA, 2013. http://doi.org/10.7289/V5NZ85MT