GENERAL INTRODUCTION 

 By Will Scott 



I have been asked by the Division of" Fish and Game of the Department 

 of Conservation, State of Indiana, to write an introduction to Mr. DeRyke's 

 paper on the "Food of Fishes" to show the relation of such work to the pro- 

 duction of fish. 



First of all, I want to emphasize the fact that our streams and lakes 

 are not waste areas. Aside from the great values that they have as places 

 for recreation and their important relation to drainage and water power 

 they are capable of producing crops equal to, if not greater, than those pro- 

 duced on the land. Without discussing this in detail the fact may be pointed 

 out, that in pre-war days the carp ponds of China rented for thirty dollars 

 per acre cash rent. This is an income of 10 per cent on a $300 valuation or 

 6 per cent on a $500 valuation. Not much farm land is worth more than 

 that. The crops from our waters are harvested for the most part as sport, which 

 makes us sometimes forget that these crops must be produced. 



In order to raise any crop of plants or animals economically it is neces- 

 sary to know many things. This knowledge is more nearly complete for land 

 crops than for water crops, or to put it technically, agriculture is more nearly 

 a science than is aquiculture. In agriculture we know something of soils, the 

 things needed to maintain their fertility, and the kind and amount of seeds 

 that will produce the best results. 



When stockraising is added, we know something of breeds, the amount 

 and kind of food they require, and their general care. 



To cite a few specific instances: we know the amount of seed wheat 

 or seed corn required per acre to produce the best results. In general, we 

 expect 100 pounds of pork for each 13 bushels of corn, etc. 



There is this difference between land and water crops. Land crops can 

 be produced by pure culture methods, that is, when we raise corn nothing 

 else is permitted to grow in that field. The hogs that are to eat the corn 

 do not touch it until it is mature. This is because the crops can be marketed 

 and fed dry. 



Water crops on the other hand must be grown in mixed culture. For 

 instance, a black bass may feed chiefly on minnows, the minnows feed on 

 small Crustacea, worms, and insect larvae, and these feed on still smaller ani- 

 mals, plants, and plant debris. This food chain may be varied and is 

 different for the different fishes. Many fishes are supported by very complex 

 food chains. In order to produce the end product the whole chain must be 

 looked after, and be kept going at its best all of the time. The minnows 

 must have suitable places to breed, there must be an adequate supply of 

 plants, etc. If one part of this food chain becomes reduced everything in the 

 food chain above it is either checked in its growth or reduced in numbers. 



In order to raise fishes it is necessary that we know, not only what fishes 

 eat but also how much they eat, and the number of pounds of fish a given 

 amount of each of these foods will produce. Not only that but we must know 

 how much of these foods is present in the various waters of the state. The 



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