SEEN WITH THE EYE OF A FISH 25 
explanation why we so seldom see a dead dace, roach 
or rudd in our ponds and rivers. The balance of a fish 
is maintained by the action of the pectoral and pelvic 
fins, and of these there is one on each side. If a healthy 
fish inclines, say, to the right side, automatically with a 
down stroke of the pectoral and pelvic fins on that side 
he restores his balance ; but a weakly or dying fish loses 
this perfect balancing power, and slowly turns on one 
side ; then as he realises he is going over he makes an 
effort and rights himself. These movements result in 
long gleams of light flashed through the water at regular 
intervals, and the attention of the pike, perch or trout 
is soon attracted, and he has no difficulty in catching 
his weakly prey. 
When one realises how very slightly a fish has to 
turn on his side to reveal himself, it is remarkable that 
we so seldom see a silvery glint as he dashes through 
the water. 
Watch trout shooting off a shallow into a pool above. 
It is possible you may detect the shadowy form, but 
more often than not the only indication of the position 
of the fish is the point of the wedge-like ripple as he 
leaves the gravelly bed. When fish swim rapidly they 
do so by swishing their tails from side to side, and there 
certainly would be sufficient roll of the body for the 
silvery sides to catch the light from above, were it not 
for the fact that a fish when he swims fully extends his 
dorsal and anal fins, and these, acting like the keel of a 
boat, keep him in a straight course. 
