How to obtain it. 77 



has been taking place on the one hand decay has also been setting 

 it on the other, and this decay has produced favourable conditions 

 for vegetable growths peculiar to such situations. Trout fry 

 turned into such ponds have developed into good fish, sometimes 

 in an incredibly short space of time. The cause of this rapid 

 development is to be found in the abundance of food produced 

 by the surrounding conditions, but the submerged plants have at 

 length decayed and disappeared, and with them, to a large extent, 

 the parasitic forms for which they have provided a suitable nidus. 

 As a result the trout have ceased to grow nay, have even fallen 

 off in condition ; but aquatic vegetation having been introduced, 

 in a few years the quality of the fish has improved. This needs 

 little explanation, for the cause is obvious. Therefore, when ' : 

 ponds are constructed, a sufficient quantity of suitable vegetable 

 life should be introduced. Some plants are peculiarly favourable 

 for the development of fish food, some are positively hurtful, 

 some are highly poisonous, and some actually devour fish. It 

 will be apparent, therefore, that some knowledge of the subject is 

 necessary before going to work, or the desired end may not be 

 brought about. 



A great deal more depends upon keeping up the exact 

 balance of suitable vegetable and animal life than the uninitiated 

 imagine ; and I have seen considerable sums of money sunk to 

 little purpose, in some cases thousands of pounds sterling, simply 

 because the matter has not been understood, and consequently 

 no attention has been paid to the most necessary details. It has, 

 indeed, never occurred to many minds, that the utmost importance 

 attaches to the presence or absence of various forms of vegetable 

 and animal life in the water. 



Before any serious expenditure is incurred on any lake or 

 pond, the water and its inhabitants should be accurately studied. 

 The results of dredging and the use of the tow net in various 

 waters, goes to show that in some there is an abundance of trout 

 food, whereas in others there is a great scarcity. Some contain 

 many injurious pests to fish, whilst others are free from them. 

 The study of flora and fauna is of the most vital importance ; and 

 the presence or absence of many microscopic as well as more 

 conspicuous animals, too apt to be overlooked, will often render a 



