The international moratorium on commercial whaling, one of the greatest conservation achievements of the 20th century, was implemented in 1986. While the giants of the oceans enjoyed a reprieve however, the Dall’s porpoise was being quietly slaughtered in huge numbers in Japan’s coastal waters.

For more than a quarter of a century, the Dall’s porpoise hunt has been the largest direct hunt of any cetacean species worldwide. In 2008 the Fisheries Agency of Japan issued permits for more than 16,000 Dall’s porpoise to be killed.

Dall’s porpoise, known in Japan as ‘Ishi Iruka’, are hunted off the north-eastern prefectures of Iwate and Miyagi between November 1st and 30th April, and off Hokkaido from 1st May to 15th June and from 1st August to 31st October. Several hundred boats are licensed to hunt.

Commercial hunting of Dall’s porpoises in north-eastern Japanese waters began in the late 1920s when the introduction of engines dramatically increased catch success rates of this fast swimming species.

Traditionally the meat was used for local consumption and the annual catch stood at least than 5,000. By the early 1980s however the hunt had expanded to the Sea of Japan and southern Okhotsk Sea with an annual catch of between 10,000 and 13,000.

In the mid-1980s the hunt dramatically expanded again. This was due to market demands: to substitute for a lack of striped dolphins which had been severely overhunted in the south of Japan and to replace baleen whale meat following the introduction of the 1986 moratorium on commercial whaling. In 1988, a record 40,367 Dall’s porpoises were killed.

In 1989 the Scientific Committee of the International Whaling Commission (IWC), which included eminent Japanese small cetacean specialists, expressed grave concern over the sudden and dramatic increase in catches of Dall’s porpoise, which had reached over 40,000 in 1988. The Scientific Committee called for an immediate reduction in catches, concluding that the level of exploitation was “clearly unsustainable”. Following Japan’s failure to heed this advice, the IWC passed a Resolution in 1990, the first IWC resolution ever on a small cetacean species, calling on the Government of Japan to reduce catches to at least pre-1986 (around 10,000) levels as soon as possible, and noting that even these may have been too high.

Although the catch was initially reduced, a quota for 17,700 porpoises was then set by the Japanese Fisheries Agency in 1993 and catches have remained around that level ever since. The IWC Scientific Committee has repeatedly expressed “extreme concern” over the unsustainability of the hunt, and the IWC has passed two subsequent resolutions, most recently in 2001 urging Japan to “halt the directed takes of Dall’s porpoises until a full assessment by the Scientific Committee has been carried out”.

In recent years there has been some acknowledgement by Japan’s Fisheries Agency that the management and conservation of Dall’s porpoises is inadequate. Having used abundance estimates from surveys dating back to the late 1980s, population estimates from new surveys were finally published in 2007 (based on survey data from 2003 but also including much older survey data to extrapolate to areas not covered in the new survey). The new estimates were lower than previous estimates: 173,638 dalli-type porpoises (CV=0.21) and 178,157 (CV=0.23) truei-type porpoises.

In 2007, the catch quotas were fractionally lowered for the first time in 14 years. In 2008, the quotas were lowered once again, and currently stand at 8,396 dalli-type porpoises and 7,916 truei-type porpoises for the 2008-09 hunting season; in total 16,312 porpoises.

Japanese Fisheries Agency papers have also stated that Japan is considering other methodologies to manage the hunt, notably the Potential Biological Removal (PRB) method, which calculates sustainable threshold levels of mortality and is used in the United States to evaluate cetacean bycatch. A paper comparing various methodologies to evaluate mortality levels in small cetaceans found that even the least conservative method would generate catch quotas more than 50% lower than those currently issued in Japan (see further reading, Wade et al. 2008).

Wade, P.R., Bass, C.L. and T. Kasuya. 2008.
A comparison of methods for calculating thresholds for evaluating levels of catch of Japan’s Dall’s porpoise (Phocoenoides dalli) hand-harpoon hunt. SC/60/SM24 presented to 60th annual meeting of the IWC Scientific Committee in Santiago, Chile. Copies available from the IWC Secretariat .

Iwasaki, T. 2008 Dall’s porpoise assessment by National Research Institute of Far Seas Fisheries. (Japanese only)

2008 report of the IWC Scientific Committee’s Small Cetacean
SubCommittee

EIA Report (2002) The facts behind Japan’s whale, dolphin and porpoise hunting
(available in English & Japanese)

2001 IWC Resolution

C. Perry, 1999. Status of the Dall’s porpoise (Phocoenoides dalli) in Japan.
SC/51/SM46 presented to the 51st meeting of the IWC Scientific Committee in Grenada.
Copies available from EIA.