ONCE AGAIN ON FACTORS LIMITING THE NUMBER OF PACIFIC SALMONS (ONCORHYNCHUS SPP., FAM. SALMONIDAE) DURING THE OCEANIC PERIOD OF THEIR LIFE

Abstract

Two different views on factors limiting the abundance of pacific salmons in the marine period of their life are compared. According to traditional point of view, food resources are limited in the marine and oceanic epipelagic biotopes, so a strong competition for food exists between different species of genus Oncorhynchus or between pink salmon O. gorbuscha and other species that makes theIr abundance lower and biological conditions worse. Negative anomaly of the sea surface temperature is considered traditionally as a factor controlling the salmons distribution in the ocean because of the food supply worsening. The other point of view is proposed by authors in the 1980s and is based on comprehensive ecosystem studies of the Far Eastern Seas and the North Pacific. Following to this view, the food resources do not limit the abundance of salmons, which play secondary roles in trophic networks within the subarctic epipelagic layer. Besides, these data do not confirm stenotherm habits of salmons, particularly in conditions of low temperature (salmons could be found in the northern Bering and Okhotsk Seas even in winter). In favor of the latter view, new data are presented for 2018, when the highest biomass of the Russian salmons was observed, primarily due to pink salmon abundance, and the absolutely record Russian catch of pacific salmons in 677,200 t was landed.

Keywords

• pacific salmon
• trophic relations
• competition for food
• temperature anomaly
• stock dynamics
• carrying capacity
• food supply