Scattering Layers — Bary 
179 
athwart the direction of movement of the 
water masses. Relevant to these points, it is 
of interest to note that the present examples 
of scattering are predominantly from two 
areas where mixed waters are believed to be 
present. One of these is to eastward of South 
Island, and is associated with the supposed 
area of disturbed water from the Chatham 
Rise obstruction. Moreover, the subtropical 
convergence migrates seasonally across this 
area, although its relationship to present ex- 
amples of scattering is not known. The sec- 
ond area, in the south west of South Island, 
is believed to be associated with mixing be- 
tween waters of subantarctic and subtropical 
origins (Deacon, 1937). 
The records presented from New Zealand 
waters appear to be similar in essentials to 
those made elsewhere. Their chief value lies 
in showing that development of scattering is 
fairly widespread in the area. Two features 
are noteworthy. Several records have illus- 
trated the successive descents from the sur- 
face of two or more separate layers, and 
conversely, the ascents up to the surface of 
distinct layers. Development of multiple lay- 
ering during the descent or ascent of a layer 
has frequently been recorded, but the writer 
is unaware of any published records in which 
such a separation into layers persists up to the 
surface, or develops at the surface prior to the 
descent of the organisms. 
The second feature is illustrated in Figure 
8. It is a matter for frequent conjecture 
whether scattering is caused by planktonic 
animals, notably euphausiids (Boden, 1950; 
Moore, 1950), or whether it is caused by 
predatory fish accompanying and feeding on 
planktonic organisms which are undergoing 
vertical migration (Hersey & Moore, 1949). 
In Figure 8, the large, dense masses of scat- 
tering have the appearance of fish shoals. 
Also, the distinct layers, present in the left- 
hand mass, are strongly suggestive of scatter- 
Fig. 9. Probable fish record made earlier in the day 
than that in Figure 8; "Discovery II” record, D3. 
