226 The Fishes of the Lower Wharfe Basin. 
limestone formation, no amount of fishing appears to denude 
the streams of its inhabitants, but in waters which are subject 
to sewage contamination, artificial stocking has to be employed, 
sometimes on a very large scale, to produce satisfactory results. 
The Trout occurs from the source of the Wharfe to as far as 
Tadcaster. It is found in abundance at Grassington, Bolton 
Abbey, and Ilkley, but in the lower portions of the river is 
not by any means as plentiful as one would desire, though 
the fish in the lower reaches are finer in flavour, better pro- 
portioned, heavier, and more handsomely coloured than those 
above Otley. At Collingham examples weighing a pound are 
not uncommon. Hofland mentions that at Harewood a fish 
was taken (1830-40) which weighed nearly four pounds, and 
quite recently a specimen of two pounds fourteen ounces was 
recorded from Linton. The present writer has had very fine 
specimens from the neighbourhood of Thorparch. Attention 
has been drawn to the superlative colouring of these fish from 
the lower reaches, and in my opinion they form part of the 
original stock indigenous to this stream, and as such have so 
far remained unimpaired by mixed blood from the hatcheries. 
It is quite possible that if the weirs at Tadcaster, Boston Spa, 
Thorparch, and Wetherby were made available for the passage 
of the Trout in their autumnal ascent to the upper waters, 
we should eventually be able to take them in larger quantities. 
Seeley says that ‘one form of disease to which Trout are’ 
liable, the nature of which is unknown, is characterized by 
an increase in the size of the head and a wasting of the body.’ 
This is often noticed in Wharfe fish, as is also the presence of 
lice, which attach themselves to the external surfaces, more 
particularly during the hot weather. In age the Trout may 
live from fifteen to twenty-five years. 
THE GRAYLING prefers the more gentle portions of rivers, 
and the lower half of the Wharfe, where it exists in large 
numbers, is well adapted for its home. Until recently the 
Grayling was a local fish, and principally confined to some 
few rivers of the central plain east of the Pennines. It has 
been suggested that it was introduced from abroad by the 
monks, as it is usually found in rivers upon the banks of which 
"are the remains of religious foundations of Cistercian origin. 
This supposition, however, is open to doubt, as the transporta- 
tion of the fish is very difficult. In some parts of the country 
weights of five pounds are recorded, though examples from the 
Wharfe weighing above a pound are comparatively rare. 
Should the water be pure they increase so rapidly that large 
rivers are well known to have been stocked by the introduction 
-of some half-dozen fish. The Grayling feeds on the surface 
all through the year, though it is most easily captured on the 
-artificial fly in the months of October and November. The 
Naturalist, 
