Records of Scattering Layers from New Zealand Seas 
B. M. Bary 1 
Hitherto the scattering of the ultrasonic 
pulses of echo sounding equipment attributa- 
ble to biological agency (Johnson, 1948; 
Kampa and Boden, 1954$) has not been re- 
corded from New Zealand waters. However, 
Dietz (1948) reported on occurrences, over 
extensive areas, of the deep scattering layer 
in the Pacific and Antarctic oceans, and on 
this ground alone, the presence of scattering 
in New Zealand waters could be expected. 
Recent investigations of occurrences and dis- 
tribution of plankton in New Zealand waters 
(Bary, in press) suggest an abundant zoo- 
plankton, and it would appear also that 
suitable hydrological conditions for the nec- 
essary concentrations of organisms may exist 
in the disturbed, mixed waters which occur 
within the New Zealand area. Again, large 
shoals of pelagic fish are frequently seen in 
the coastal waters. It is therefore consistent 
that records are available which show scatter- 
ing of sound from both plankton and fish. 
The notes which follow deal briefly with 
some of these records from New Zealand. 
Both deep and shallow scattering layers, mul- 
tiple layering, and scattering from fish shoals 
are discussed. One record is believed to show 
scattering from layers of zooplankton which 
are associated with a shoal of fish. Other 
records illustrate two related phenomena, that 
of separated multiple layers maintaining their 
identities throughout the ascent to the surface 
at night, and the converse— the differentia- 
tion and subsequent descent of separate layers 
from the surface at dawn. 
ACKNOWLEDGMENT 
I am grateful to Mr. J. W. Brodie, Super- 
intendent, New Zealand Oceanographic In- 
1 New Zealand Defense Scientific Corps, Navy Of- 
fice, Wellington. Present address: Oceanographic Lab- 
oratory, 78 Craighall Road, Edinburgh 6, Scotland. 
Manuscript received July 24, 1956. 
stitute, for granting access to the collection 
of fathograms housed at the Institute. 
MATERIALS 
The hydrographic survey being carried out 
by H.M.N.Z.S. "Lachlan” is a continuing 
source of fathograms of coastal and offshore 
waters. Other naval vessels and coastal and 
overseas merchant shipping have contributed 
many records from the high seas. "Lachlan” 
fathograms are particularly useful for shallow 
scattering records. The other shipping offers 
a source for deep scattering records, but in 
fact, no scattering has been detected in any 
of the fathograms from these ships. Some of 
the most useful records have originated in 
special investigations made in New Zealand 
waters by R.R.S. "Discovery II,” of the Na- 
tional Institute of Oceanography, England, 
and by the Danish Expedition in H.D.M.S. 
"Galathea.” I am most grateful for permis- 
sion to reproduce records from both of these 
sources. 
All examples of scattering have been ob- 
tained incidental to other requirements. For 
this reason the records are not always as clear 
as they might have been had the sounder 
been tuned to give maximum strength from 
the scattering layers. It is unfortunate, too, 
that promising records have been phased out 
in a number of instances; and additional dif- 
ficulties are met in the fading of some fatho- 
grams made on iodide paper. 
SCATTERING LAYER RECORDS 
The localities and lineal extent of the rec- 
ords of scattering for the New Zealand area 
are shown in Figure 1. Figures 2 to 9 repro- 
duce some examples, and a general summary 
of all occurrences is given in Table 1. 
The ascents of the two shallow scattering 
layers are shown in Figure 2, a trace made 
170 
