TROUBLED WATERS - Whale and Dolphin Conservation Society

More documents

Recommendations

Info

chance of fog decreases from 15 to 5 per cent. In the following months to November there is no clear trend. In December, the probability of precipitation is 24 per cent. These results indicate that March has the highest chance of precipitation of all the whaling months. The probability of fog is highly variable in the winter, but from September onwards, the probability of fog increases from 3 per cent to around 15 per cent in December and January. Thus, in the period when the probability of precipitation is low, the probability of fog is relatively high. So if the issue of reduced visibility is considered, fogrelated problems add to those caused by precipitation in these months. How the whalers respond to fog or precipitation is unclear, and it would be of great value if more information was made available by the whalers to help understand how these weather states affect the efficiency of whale killing. Wind speed and wave height The average wind speed, regardless of its direction, increases from 7.4 ms-1 (a moderate breeze) in January to 9.3 ms-1 (fresh breeze) in March. However, the wind speed is highly variable from April until October, with the highest variation in the months with the highest averages. These are September and October (10.5 ms-1; fresh breeze). Thereafter the wind speed reduces to 7.7 ms-1 in December. Given the variation, probabilities of wind speeds higher than 11.2 ms-1 (strong breeze and higher) in March or November, or 14.3 ms-1 (moderate gale and higher) in October are significant (10, 13 and 20 per cent respectively). The average height of the waves (calculated from the upper third of all wave heights, known as ‘significant wave height’, see also www.oceanweather.com ) and the time between reoccurrences of the most violent and energetic waves (known as ‘Tpeak’) is estimated at one location: 67.5° S and 180° W. This has been done using the GROW model of Oceanweather Inc. and is based on the years 1970 until 2001. The average significant wave height tends to increase from 2.2 to 3.4 metres between January and March and tends to remain relatively high until June with an average wave height of 3.2 metres. The height is not known for the following months, but averages 1.9 metres in December. The missing values are for months in and after the winter, when the ice covers the sea. The model excludes data in these cases. The Tpeak seems to follow the same trend as the wave height, starting with around 10.5 seconds in December and January and increasing thereafter to about 11.5 seconds in the period April to June. The wind increases from January until March, but becomes more variable thereafter. This together with the growing percentage of ice in the area, blocking wave formation after March, may explain why the highest waves are found in March before the significant formation of sea ice. It can, therefore, be postulated that March may be one of the most severe months (in terms of adverse weather conditions) in which to perform whaling operations in the research area. Ship motions in March and December at an Antarctic whaling ground Ship motions have been calculated using the SHIPMO computer programme of the Maritime Research Institute in the Netherlands (Anon 2002). The ship used for these calculations was similar to the Japanese whale catching vessel Toshi Maru No.25. A sailing speed of 6 knots, head seas coming in at 30 degrees and local sea depth of 1,000 metres were used in the model. The model was run for estimated sea conditions during March and December, as described above. The motions considered were, the sway (from left to right), heave (up and down) and surge (forward and backward), as would be experienced at the level of the harpoon on top of the bow. Table 1 provides the results for these different motions in December and March. WEATHER, SEA CONDITION AND SHIP MOTIONS AFFECTING ACCURACY IN WHALING 65
66 A REVIEW OF THE WELFARE IMPLICATIONS OF MODERN WHALING ACTIVITIES Table 1. Significant peak-to-peak sways, heaves and surges December March Sway mean 0.61 1.20 st. dev. 0.17 0.37 N 658 (11) 386 (6) Heave mean 1.82 3.37 st. dev. 0.57 1.23 N 224 (4) 116 (2) Surge mean 0.26 0.62 st. dev. 0.10 0.22 N 531 (9) 226 (4) Table 1. Significant peak-to-peak sways, heaves and surges (in metres) on the basis of the SHIPMO model and at 6.5 metres above the waterline at the bow of a ship comparable to a Japanese whale catcher sailing at six knots in December and March with 30 degrees head waves as characterised in the forelast paragraph. N is the number of samples in the upper third of the frequency distribution taken during one hour. The number in one minute is in brackets. The results of conditions in March demonstrate that six sways averaging 1.2 metres, two heaves averaging 3.4 metres and four surges of 0.6 metres, could be expected each minute. When the model was 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 effect on accuracy when only one heave is considered. In this figure the height of the harpoon above sea level is ´h´ and the horizontal distance between the harpoon and a whale is ´d´. Thus, a theoretical line 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 (which at the least equals half a peak-to-peak heave) would give a substantial change (y) in projection of the harpoon. In the example y would be 5.5 metres when the heave is 1.8 metres as might be y Figure 1. A relatively small increase (x) in the height (h) of the harpoon as a wave lifts the bow of the ship, results in a large change in projection (y) of a harpoon aimed just before the wave at a whale at a distance (d) from the whaling ship, which would have to be compensated during the wave motion in order to try to maintain the aim (for further explanation see the text). d X h
Page 1 and 2:
TROUBLED WATERS A REVIEW OF THE WEL
Page 3 and 4:
II A REVIEW OF THE WELFARE IMPLICAT
Page 5 and 6:
IV A REVIEW OF THE WELFARE IMPLICAT
Page 7 and 8:
2 A REVIEW REVIEW OF THE WELFARE IM
Page 9 and 10:
4 A REVIEW REVIEW OF THE WELFARE IM
Page 11 and 12:
6 A REVIEW OF THE WELFARE IMPLICATI
Page 13 and 14:
8 A REVIEW OF THE WELFARE IMPLICATI
Page 15 and 16:
10 A REVIEW OF THE WELFARE IMPLICAT
Page 17 and 18:
12 A REVIEW OF THE WELFARE IMPLICAT
Page 19 and 20: 14 A REVIEW OF THE WELFARE IMPLICAT
Page 69: 64 A REVIEW OF THE WELFARE IMPLICAT
Page 105 and 106: 100 A REVIEW OF THE WELFARE IMPLICA
Page 121 and 122:
116 A REVIEW OF THE WELFARE IMPLICA
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Appendix II Colour plates ©Mark Vo
Page 147 and 148:
Page 149 and 150:
Figure 13. Processing minke whales
show all

TROUBLED WATERS - Whale and Dolphin Conservation Society

Create successful ePaper yourself

Delete template?

Save as template?