38
THE BIOLOGY OF FISHES
conditions—, temperature, and salinity of the—water. But
it hastobe remembered, that during millions
this
'
pelagic form has become adapted to a much wider range of
variations in these conditi0ns than the North Sea and
Norwegian Sea can now show, even from winter to the height
’
And it seems
more
probable that the
wanderings at
rate are simply dictated by hunger and
need of food.
Formerly it was thought that they were
restricted in their
organisme ; but it has
been shown
that a very large proportion
”of their food consists of fish; particularly young Sand—etais.
,
In the winter the latter migrate out from the coast into
desperzwater to
and here in
spring the young
are
pursued by the Herring,
pursued by the
'
Cod, Haddœk "and Mackerel, etc“... :Ïn"short,:it is probable
that the biological conditions,food—,ancl‘ëscape from eneiiës,
now the main determining inuences in" the wandenngs
'
-_of:thG:—H<ärring;g
7
.
1 _;
_
othershes u—nd6rtal{e Wanderingsgisom‘e,ofÏgreater
êb'i1t these
'
,
-
scientists in- many
to
Final Solutions,
—be expected ;" that has become very
apparent,from the intensive inve$tigations of recent years.
Even1f :all the factors determining; the _Wadengsgand,
0? .the:reverse Wereknownandalsothelrlelatwe1
:
1mP0rtancetheyaresocloselymterwoventhatonlya
"
andotherGad01dSbytheshmghas had a great deal
to . do;
abundance in
Ÿ
theNorthSea dur1ng—Îhefpa3t
. ’
»
{But
1 in‘ ‘ this
*
as111 $C ,
iŸ!ÏOÎ61} problems : connected -‘With‘c the
Î
”measure Ÿf»or comparison W1ththe
_
,.factQrs,.inuencingthe‘-quantitiesyoffHerring;ï— Fluc—
.
1
_» :ÎÏ‘lê—üOns haVÇibeefgÿî_traÇed right back to thèî épawnipg; îthat
'
-._
i
.
years
:
_