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PACIFIC SCIENCE, Vol. XII, April, 1958 
for 15 minutes (around 2200 hours), and then 
rises slowly. Sunset was at 1930 hours (mid- 
February, 1954) and darkness would have 
fallen about an hour before this trace was 
commenced. The trace is of even texture with 
a suggestion of subsidiary layers within the 
main one; it is probably the result of scatter- 
ing from zooplankton. If so, the record 
illustrates a curious reversal in the expected 
direction of movement of the organisms. It 
is possible that this special reaction is an 
effect of moonlight. The moon was in the 
first quarter and crossed the meridian at about 
2130 hours on the day in question. 
A "Discovery II” record (Fig. 8) made 
when approaching Foveaux Strait from the 
west (D3, in Fig. 1) is of strongly developed 
scattering most of which is remaining at 
depth. Sunset was at 1700 hours (May 1951), 
there was no moon, and it would have been 
dark for some time before 1950 hours when 
the record begins. The unevenly distributed, 
dense patches in this trace suggest that fish 
may have been the chief cause of the scatter- 
ing. Fish do not necessarily perform diurnal 
migrations, and thus the fact that the main 
body of the scattering organisms is not 
ascending might be explained. On the other 
hand, three or four distinct layers can be 
detected in the earlier (left-hand) one-fifth of 
the record. These penetrate the fish scattering 
and are ascending towards the surface at rates 
of 2.0 to 2.5 m. per min. Their appearance is 
suggestive of scattering from planktonic or- 
ganisms. This record may be indicative there- 
fore of fish following and feeding on concen- 
trations of plankton which are undergoing 
normal vertical migration. 
Some other records are available, believed 
to be of scattering from fish shoals. Figure 9 
illustrates one such record, made in the west- 
ern approaches to Foveaux Strait by "Dis- 
covery II,” earlier on the same day as that 
Fig. 5. The dawn descents of separated layers fol- 
lowed by splitting of each of the layers. The heavier 
trace in the second layer is suggestive of larger animals 
being present; "Galathea” record, G3. 
