184 TJ. S. BUREAU OF FISHERIES 



Soybean meal has given good results when used at the rate of 575 

 to 700 pounds per acre during the season. Our maxinnnn production 

 of black bass fingerlings was obtained in a pond fertilized with 

 soybean meal at the rate of 700 pounds per acre. 



In view of these results it is probable that in most cases from 500 

 to 1,000 pounds of fertilizer per acre of pond surface will be sufficient. 

 However, if a pond is notably deficient in vegetation or if there is an 

 exceptional amount of seepage, it will doubtless be necessary to use a 

 considerably larger amount of fertilizer if the best results are to be 

 obtained. 



FORAGE FISH 



The utilization of forage fish in pond culture is a comparatively 

 recent development. Although it is well known that bass and other 

 game fishes subsist largel}^ upon fish in nature most pond culturists 

 have hesitated to adopt this method of providing food for the bass 

 in their ponds. There is a more or less general belief that such a 

 course would only serve to increase cannibalism which is always an 

 important factor when bass are to be reared to any considerable size. 



It is obvious that if we are to obtain the maximum production 

 of bass or other game fishes, we must increase the supply of food as 

 much as practicable. Practically all young pondfish at first feed on 

 the plankton Crustacea and similar organisms. Many species continue 

 to feed on these organisms and insects throughout their lives but the 

 carnivorous fishes soon begin to prey on their weaker brethren and 

 after a few weeks subsist chiefly on fish. It is true that bass and 

 crappie can subsist largely on insects and Crustacea during the first 

 geason but the bass, at least, prefer fish and will grow faster on a 

 fish diet than on other foods. No practicable method has yet been 

 developed of greatly increasing the insect life in our ponds, but, 

 fortunately, this is not true of fish and many of the smaller species 

 multiply prodigiously when given the proper conditions. This being 

 the case, there is apparently no reason why we may not utilize such 

 fish to build up a food supply for our game fishes. 



As a class, the minnows are preeminently nature's forage fish, but 

 in choosing forage fish for use with bass or other carnivorous pond- 

 fishes it is well to bear in mind that not all minnows are equally 

 valuable for this purpose. On the contrary there are certain funda- 

 mental requirements which must be met if a fish is to prove satis- 

 factory for forage purposes. Possibly the most important of these 

 is the avoidance of direct competition with game fishes for food. 

 Since all young fish apparently feed at first on animal plankton it 

 is impossible to find a forage fish which will not compete with the 

 young of carnivorous fishes to some extent, but it is important to 

 avoid species which will require the same food as the game fishes 

 for any length of time. This, of course, rules out all predacious 

 fishes no matter what other desirable characters they may possess. 

 If otherwise satisfactory, the most desirable species are undoubtedly 

 those which feed principally upon vegetable material. They utilize 

 a food supply w^hich is not directly available to game fishes and, if 

 readily eaten by them, form a convenient means of converting algse 

 and vegetable debris into edible fish. 



