TROUBLED WATERS - Whale and Dolphin Conservation Society

Table 1. Significant peak-to-peak sways, heaves and surgesDecemberMarchSway mean 0.61 1.20st. dev. 0.17 0.37N 658 (11) 386 (6)Heave mean 1.82 3.37st. dev. 0.57 1.23N 224 (4) 116 (2)Surge mean 0.26 0.62st. dev. 0.10 0.22N 531 (9) 226 (4)Table 1. Significant peak-to-peak sways, heaves and surges (in metres) on the basis of theSHIPMO model and at 6.5 metres above the waterline at the bow of a ship comparable to aJapanese whale catcher sailing at six knots in December and March with 30 degrees head wavesas characterised in the forelast paragraph. N is the number of samples in the upper third of thefrequency distribution taken during one hour. The number in one minute is in brackets.66A REVIEW OF THE WELFARE IMPLICATIONS OF MODERN WHALING ACTIVITIESThe results of conditions in March demonstrate that six sways averaging 1.2 metres, two heavesaveraging 3.4 metres and four surges of 0.6 metres, could be expected each minute. When the modelwas run using sea conditions expected during December, sways and surges were reduced by half,while the average heave was 1.8 metres. However, the numbers of sways, heaves or surges per minute,was twice that which would be expected under the March simulation. Figure 1 illustrates the effecton accuracy when only one heave is considered. In this figure the height of the harpoon above sealevel is ´h´ and the horizontal distance between the harpoon and a whale is ´d´. Thus, a theoreticalline between the aimed harpoon and the whale would make a triangle with height h and base d.Suppose h is 6.5 metres and d is 40 metres as in a whaling operation. Then an increase x of h (whichat the least equals half a peak-to-peak heave) would give a substantial change (y) in projection of theharpoon. In the example y would be 5.5 metres when the heave is 1.8 metres as might beyFigure 1. A relatively small increase (x) in the height (h) of the harpoon as a wave lifts the bow ofthe ship, results in a large change in projection (y) of a harpoon aimed just before the wave at awhale at a distance (d) from the whaling ship, which would have to be compensated during thewave motion in order to try to maintain the aim (for further explanation see the text).dXh