Marine mammals in macro-ecosystems of the Far Eastern seas and adjacent waters of the North Pacific

This article considers the role of marine mammals in a sea or ocean ecosystem based on the example of the Far Eastern seas with adjacent waters of the North Pacific, which is one of the regions of the World Ocean that is distinguished by its high biological and fish capacity and by a high abundance of cetaceans and pinnipeds. Based on extensive data, which was published mostly by Russian experts, the authors have estimated the quantities of annual consumption of fish and invertebrates by marine mammals in three Far Eastern seas: 14.6–18.2 million tons in the early 20th century; 12.3–15.1 million tons in the late 1970s; 22.7–28.8 million tons in the pre-harvest period; and 24.0–24.7 million tons in the early 21st century (27.0–29.5 million tons, if 3–5 million tons in ocean waters off the Kuril Islands and Kamchatka are taken into account). More than half of this quantity is formed by zooplankton and zoobenthos; the second largest portion consists of fish and squid. At the same time, the values of food consumption by fish and large invertebrates are much higher than these estimates for the 0–1000 m layer: 516 million tons were consumed in the 1980s–1990s; 389 million tons in 1991–1995; and 461 million tons in 1996–2005. In the years of high abundance, large walleye pollock alone consumed nearly 40 million tons of small fish and squid. Based on the data of 35-year-long ecosystem studies that were conducted by the Pacific Research Fisheries Center (TINRO Center), the following biomass estimates have been obtained for the biota of the Far Eastern Economic Zone of Russia: mesoand macroplankton, 1000 million tons; zoobenthos, 500 million tons; nekton, 100 million tons; benthic fish, 5 million tons; and large benthic invertebrates that are not included in the benthos, 2.43 million tons. By using these estimates and by comparing the quantities of food consumption by marine mammals, the conclusion was made that the role of marine mammals in food webs of waters of the Russian Far East is remarkable, but it does not reach a level that is high enough to regulate such a large-scale ecosystem as the macro-ecosystem of a sea or ocean.