…
THE BIOLOGY OF FISHES
,
,
'
With the Outpouring of chemiéal waste—products into the
‘
water has had a Serious effect on the sh population of the
—
rivers.
The Thames was once a Salmon“ river in days
‘
'
long gone by, and some stragglers have—occasionally
been
seen at the mouth trying to enter, but nene are now caught '
in the river.
The Salmon has almost di3appeared also
'
from ÏŸthe Elbe and Weser.
.
:
_
,
As the result of change from warth cold water or from
'
soft to hard water, shes may Suffer just as
The
skin begins to pee'l in various
and serious wounds
may deVelop. These may heal; after a few days, but in the
meatime— some dead—ly enemy may seize on
exposed
f
form of either “plant— or animal parasite. So
theïshremains Strong and— healthy,
even if the
;
parasite is ;plaC—ed deliberately on the exposed par—t (Edington,
.
}15àbie
When
Salmon, ‘:forlexample, has b_eëoÏfhefexhauStedÿ byspawning and. ghting” With—its
,
(Saprolegnià) makes its
and— ràpidlÿ covers the
sh with soft thread-like outgr‘owth& This was
L—_
thought to be the cause of heavy and frequent
:
‘
amongtheSalmôn-in Scottish (and Irish) rivers, butit; has ,
_:
{that “an even more
-
'
has previous1y; been-at Work. Thispest is
; ,
salinonis pestis‘, Which Ïgrows best1ncoldwater, _'
'Î
thus intheawîntér
theSalmonarespawmng
.
-
themfromthewaterasseonasposmbleThe
eXpOS€d=
a;
time in uncleanair,buth€realsc>1t13
that_btliér -.
;;
parasitesÇêbegin'theî' trouble, forjeàrpk,îinÇ “the .
,
:—'i_ kidneys,ïand weaken thesh tôïÏèuch
_Çànot
_
,
,
resist
It
ï
'
îÎï ' îhàtzibäCtea :ile - behind the
‘