320
THE SEAS
—
to the shing industry, the herring, indeed, being one of the»
important of all sh
the waters on the north—
eastern part of the Atlantic. The plaice make up a large part
.
of the catches of the.traWlers in the North Sea while the
pursuit of the herrig constitutes that great drift—net shery
-
which takes place . around our coasts chiey in the late
autumn and winter. This distinction points at once to a”
_
fundamental difference in the behaviour of these two
sh.
The plaice which are captured by the trawls that
scour - the sea oor are bottom—living or demersal sh,
while the herring; as their mode of capture suggests, live,
for considerable
at any rate, in the water layers
.
above the bottom and are pelagic.
'
—
In studying-the lite—history of a sh it is best to start
right from the beginning and watch the growth and movements of the individual from the time it is rst brought
forth by the parent sh as an egg.
_
Let us, therefore, put ourselves in the place of the early
naturaliSts,
founders of shery research, and imagine
that we must setoutto nd the eggs of the herring and the
_
; We should immediately say,
“
How can we nd
'
them if _We do not know what they are like to look
? ”
Thisbringsf us to the very rst step in the stùdyof
of
sh.=
The, eggs when discovered must be accurately
.
described and gured _so that those who come after us
'
may know at once what to lookfor.
_
»
.
Towards the end of the nineteènth century a controversy
arose as to whether the. advent ofthe steam trawler might
'
_not have a' harmfuleect on the seasheries by destroying
inlarge quantities the eggs of_thesh as the heavy net was
"
dragged
the
In- the year 1864 the great _
_
Norwegian naturalist, Prof, G.
Sars,- discovered large '
numbers of
surface water layers well 7
above the bottom, audi Was able to show that _these Were
_