.
.
FISHERY RESEARCH
321
the eggs of the cod.
This discovery stimulated the search
for the eggs of other sh and it has since been found that,
—
with only one exception," all our food sh have these drifting
.
eggs.
This early piece of shery research immediately
showed its practical value ; for, when the discussion arose
about the necessity of putting restrictions on steam-trawling '
because of the supposed destruction of eggs, the scientic
,
advisers were able to show that no such danger existed. -
It has been said that there was one exception to the rule
that our food sh have pelagic eggs.
This exception is
the herring, whose eggs (Plate 112) stick in clumps to the
bottom (see page 80).
In this case however there is little
'
risk of their destruction by the trawls, because the eggs
lie well down in the crevices between the stones on the
rough ground on which they are laid, apart from the fact
‘
that the rough grounds on which the herring spawn are
'
generally so rocky and strewn with boulders that they are
unsuitable for trawling.
The eggs of the plaice and the herring having been accur—
ately described and identied by means of articial fertiliza—
tion and by hatching, we can now proceed in our search for
the spawning grounds of these two sh.
There are two
_
obvious ways of searching for these localities, rstly by seek— .
ing for the eggs themselves and secondly by nding
from the
,
statistics of the shing industry at what “places most
of
the sh containing ripe roes were caught.
The last method
obviously involves the least trouble (given the necessary
Statistics), but it has the disadvantage-that the results
.
are Only approximate, as there is no-evidence that the‘sh
:
would have actually spawned' where they were —càught
'
:
since they can swim a consider'able distance in. a short
space of time.
Let us then consider the rst method.
Having roughly
, —
marked out the 'spawn‘ingregion'by means of the
statistical
_