Performance of the Whale-Finder

(from "Kujira to Inbou" (Whales and Plots), by Yoshito Umezaki, 1986)

Note:
1. The words of conversations or statements which were made in English are not the exact wording as the original, because they were translated from Japanese texts in the book.

2. Remarks starting with an "*" are mine.


The anti-whaling groups who targeted banning factory ship operation in sperm whaling classified the Northeastern Pacific stock of sperm whales, with a forcible manipulation of figures, into the Protection Stock in 1977. The means they used were as follows.

Among the methods to estimate the stock population, there is the CPUE (Catch Per Unit Effort). This shows the ratio between the number of whales hunted and the amount of time in 24 hours used by a catcher boat for seeking, chasing, catching and towing whales. When the CPUE value rises, the number of whales is inferred to have increased, and if the value decreases, the number of whales is inferred to have been reduced.

At the 1977 meeting of the IWC Scientific Committee, anti-whaling scientists insisted that Japan had underestimated the performance of the whale-seeking device "ASDIC"(*1), with which catcher boats are equipped, and did not admit the Japanese data. From several years' results, Japanese scientists had concluded that using the ASDIC improved the efficiency of the catch at most 18% when compared with the cases of not using it. Japanese catcher boats sometimes use ASDIC when chasing whales. In particular, since sperm whales dive into the sea for a long time and try to swim away, ASDIC is used to chase them.

With this data, anti-whaling scientists insisted the performance of ASDIC, which could find the whales within only 800 meters, could find whales up to 12 kilometers beyond, and calculated that the ASDIC improved the catch efficiency 40%. Using this as a calibration value, then the estimated population computed was 69,000 for male sperm whales and 127,000 for females. This means that the estimated population is 41% of the initial population for male, and 78% for female, and the male sperm whale was classified as Protection Stock.

Using the Japanese figure of 18% improvement in efficiency, the computed population was 132,700 males and 243,600 females. This meant that male sperm whales were above MSY Level to be classified as Sustained Management Stock. However, in the report of the Scientific Committee, the views of anti-whaling scientists was reported as majority opinion, and the plenary session adopted the classification of male sperm whales as Protection Stock.

As a result, Japanese factory ship sperm whaling, which hunted the Northeastern Pacific stock of sperm whales had to stop operation since 1980 season. It did not mean that the female sperm whale was also classified as Protection Stock. The reason was, regardless of stock status, that the form of 'factory ship operation' was bad.

In the case of the Western Pacific stock of sperm whales, which were taken by coastal whaling operations, the estimated population of adult whales (which were the target of the hunt) was about 200,000. Since anti-whaling scientists could not find reasons to classify this stock as Protection Stock, the analysis using the computer was then stopped. The reason was that no budget was available. But the Secretariat of the IWC was not informed of this reason.

1 It seems that the device ASDIC was named after 'Anti-Submarine Detection and Investigation Committee' of the UK established during WWII.

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