The Institute of Cetacean Research
Fin Whale Abundance Estimation in the North Pacific – Research Findings Published Online in the Journal of Sea Research
December 18, 2025
Designated Corporation for Scientific Whale Research
THE INSTITUTE OF CETACEAN RESEARCH
Summary
･Large-scale sighting surveys covering the North Pacific, including waters around Japan, were conducted, enabling the first-ever estimation of the fin whale population across the North Pacific.
･The new abundance estimates suggest a recovery of the fin whale compared to the 1976 abundance, when commercial whaling of this species was suspended.
･Abundance estimates suitable for fin whale resource assessment were obtained.
Overview
The fin whale (lower right in the figure below) is a pelagic large baleen whale species widely distributed worldwide. Fin whales inhabit the entire North Pacific Ocean, including the waters around Japan, feeding primarily north of 40ºN latitude during summer and breeding in lower-latitude waters during winter. This species, the second largest baleen whale species after the blue whale, was heavily exploited by commercial whaling since the early 1900s. Commercial catches were halted in 1976 due to regulations by the International Whaling Commission (IWC). Since the 1980s, the Government of Japan has been conducting sighting surveys using dedicated research vessels in the North Pacific to study the abundance and distribution, and the recovery of the species after past exploitation. Since 2010 research surveys have been conducted in cooperation with the IWC for parts of the North Pacific.
The ICR research team estimated the abundance of fin whales based on sighting surveys conducted between 2008 and 2022, which covered 28,770 nautical miles (approximately 53,300km) through most of the North Pacific . These surveys covered the species’ known summer distributional range in the North Pacific extending from 135ºW, 35ºN off the coast of Japan into the Bering Sea (see the figure below). The surveys design and analytical approaches were in accordance with guidelines established by the IWC and were conducted with common equipment on all vessels to maintain data consistency.
This is the first time such a broad-scale abundance estimate of the North Pacific fin whale has been obtained. The results, published in a peer-reviewed journal, indicate that the current summer abundance of fin whales in the entire North Pacific, south of the Aleutian Islands is 45,344 individuals (Coefficient of Variation (CV) = 0.167) and that in the Bering Sea is 10,234 individuals (CV = 0.202). These results suggest that fin whale has been recovering since 1976. These new abundance estimates can be used for assessment purposes in the context of conservation and management of this species in the North Pacific.
The paper, authored by Megumi Takahashi, Koji Matsuoka and Takashi Hakamada, is:
First large-scale abundance estimates of fin whales (Balaenoptera physalus) in the North Pacific: Implications for management. Journal of Sea Research, Volume 208, 2025, 102647, ISSN 1385-1101, https://doi.org/10.1016/j.seares.2025.102647
