178 "D". S. BUREAU OF FISHERIES 



Although it is not practicable to spawn pondtish artiticially, the 

 production of fry in large numbers at a reasonable cost presents no 

 great difficulties, and until quite recently little attempt was made to 

 grow bass to a larger size. But, as in the case of trout, it is becoming 

 more and more evident that fry are of relatively little value for 

 stocking purposes and that if we are to maintain good angling in 

 bass waters we must plant larger fish. It is probably true that in 

 some localities, where conditions are exceptionally favorable and 

 there are few predacious fish, fry may give a good account of them- 

 selves, but such cases are the exception rather than the rule. If the 

 bass fry are retained in rearing ponds until fall, they will have 

 reached a length of 3 to 4 inches or even more and are consequently 

 well able to fend for themselves. 



When we attempt to rear large numbers of bass, or other pond- 

 fishes, we are immediately confronted with the problem of provid- 

 ing the fish with an adequate food supply. The most obvious solu- 

 tion is to feed some artificial food such as meat or dry meals, but 

 this is not as simple as it seems. Unlike trout most pondfish do 

 not take readily to an artificial diet, and although brood bass, for 

 instance, may be taught to eat fresh meat it is questionable if this 

 is the best solution of the problem. 



A more logical method, and one which we believe will prove 

 more practicable in the end, is to make the ponds self-sustaining 

 so that the fish can subsist on natural food produced in the ponds. 

 It is doubtless advisable in some instances to supplement this with 

 additions from outside sources but, in general, we believe, it will 

 prove more economical to rely mainly on the natural production of 

 the ponds. 



The production of fish food in ponds is by no means a simple 

 matter; and if satisfactory results are to be obtained, a thorough 

 knowledge of the principles involved is essential. In pond culture 

 we must deal with a complex series of interacting physical, chemical, 

 and biological factors with relationships to each other, which are 

 often far from clear and are not always easily subjected to investi- 

 gation. All organisms are dependent on a complex of factors for 

 their existence and development, and if we are to get the best results 

 we must know how to maintain the proper balance of these factors to 

 insure optimum conditions for the propagation and growth, not 

 only of the fish, but of the myriads of organisms which directly or 

 indirectly enter into their food supply. Just as cattle and sheep are 

 dei)enclent on forage crops so the fish in our ponds are dependent 

 on alga? and other aquatic plants for their basic food supply. But 

 unlike cattle and sheep our game fishes, for the most part, do not 

 eat the plants directly. Instead there are series of organisms feeding 

 on each other and forming food chains which start with the algae 

 and culminate with bass or other game fishes. Obviously then, the 

 problem is not only to produce the proper growth of algse and other 

 plants but also of the animals which form the intermediate link 

 between the plants and the bass. 



Believing that the success of pond culture depends on the proper 

 utilization of these various factors the Bureau of Fisheries in li'iiG 

 inaugurated a comprehensive series of investigations ijti this field 



