Features of the Oceanological Conditions as a Prerequisite for Formation of a Food Base for Gray Whales in the Marine Feeding Area (Northeastern Shelf of the Sakhalin Island)

G. V. Shevchenko1, 2, ✉, V. N. Chastikov1, Z. R. Tskhay1

1 Sakhalin Branch of the Russian Federal Research Institute of Fisheries and Oceanography, Yuzhno-Sakhalinsk, Russian Federation

2 Institute of Marine Geology and Geophysics, Far Eastern Branch of Russian Academy of Sciences, Yuzhno-Sakhalinsk, Russian Federation

✉ e-mail: shevchenko_zhora@mail.ru

Abstract

Purpose. The paper is purposed at proving (based on the data of a special field experiment) the importance of vertical tidal mixing which is conditioned by the diurnal shelf waves, on the one hand, and determines the specific conditions for forming food supply for gray whales in the Marine feeding area near the Sakhalin northeastern coast, on the other hand.

Methods and Results. The materials for the research were formed of the data resulted from the instrumental measurements of current velocities, water temperature and salinity (and their variations) in the bottom layer carried out at three diurnal oceanological stations in the Marine feeding area in autumn 2019 as well as the satellite data on the chlorophyll a concentration (2003–2017).

Conclusions. The results of the diurnal station measurements showed that in the Marine feeding area of gray whales (on the Sakhalin northeastern shelf), there was a constantly working mechanism which intensified and weakened together with the diurnal tides (cycle was a half a month). It is manifested in the diurnal seawater temperature and salinity variations near the bottom, as well as in the vertical distributions of oceanological parameters. Due to the diurnal shelf waves providing local tidal mixing, the conditions contributing to the sustainable formation of food supply for gray whales arise in this area.

Keywords

Sea of Okhotsk, tidal mixing, diurnal shelf waves, satellite data, water temperature, salinity, current velocity, chlorophyll a concentration

Acknowledgements

The authors are thankful to the LTD “Sakhalinskaya Energiya” and the LTD “Gazpromneft-Sakhalin” for organizational and financial support of the research.

Original russian text

Original Russian Text © G. V. Shevchenko, V. N. Chastikov, Z. R. Tskhay, 2023, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 39, Iss. 5 (2023)

For citation

Shevchenko, G.V., Chastikov, V.N. and Tskhay, Z.R., 2023. Features of the Oceanological Conditions as a Prerequisite for Formation of a Food Base for Gray Whales in the Marine Feeding Area (Northeastern Shelf of the Sakhalin Island). Physical Oceanography, 30(5), pp. 666-687.

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