PT^OGRESS IN BIOLOGICAL INQUIRIES, 1 :{ 4 381 



Thus, both slations afTonl cxooptioiially favorablo opporhmitics for 

 <!on(liH'tinir fiohl studios and ox|)orim<Mits in cooi^cM'ation with the 

 Unitod States Forest Service. 



I'OND-FISH t ILTUKE 



Investijrations in i^ond-fish culture durin<; 1934 were liniitvd to 

 those conducted by O, Lloyd Meehean at the Nat^-hitoches (La.) 

 station. These investi<rations are desitrned primarily to throw li'^ht 

 on problems whicli liave arisen in connection with ])ond culture in 

 the Southein States where conditions in many respects are quit€ 

 different from those found at hatcheries in the North. 



The investigations at the Natchitoches station were concerned 

 chiefly with the use of fertilizers in pond culture. Since experiments 

 in previous years have shown conclusively that proper fertilization of 

 rearing ponds results in a marked increase in the production of fish, 

 the exi)eriments during 15)o4 were designed i)rimari]y to furnish a 

 comparison of the value of different fertilizers for this purpose. The 

 results, however, are inconclusive, since no correlations were found 

 between any of the ecological groups of food organisms and the 

 amount of the different elements composing the fertilizers. It is con- 

 cluded that this was due to the fact that moi-e fertilizer was used than 

 was necessary. Consequently, there was at all times a surplus of food 

 material available. Under such circumstances it is logical to assume 

 that the production would be limited by other factors than food. 



The results agree with those obtained in 1933 in failing to show that 

 there is necessarily any correlation between the production of plank- 

 ton in a pond and the production of fish as claimed by some authors. 

 There is, how^ever, a distinct correlation between the number of Chiro- 

 nomidal larvae per unit area of bottom sample and the production of 

 fish. This indicates that fish production is dependent on bottom 

 organisms rather than on plankton. 



The experiments indicate that the number of fish produced per acre 

 is not a good index of production in a pond after bass have reached 

 a length of about 21^ inches. The greater forage area needed by the 

 larger fish and the change in food habits necessarily reduces the num- 

 ber of individuals. Consequently, with larger fish the weight of the 

 fish rather than numbers should be taken as a criterion of production. 

 This is especially important in the South ow'ing to the early spawning 

 season, the young bass usually reaching a length of 2i/2 inches by the 

 1st of June. Bass can be reared successfully to this size wnthout the 

 use of forage minnoAvs, but if they are to be kept in rearing ponds 

 through the summer the need of forage fish is clearly indicated. 



As a result of these experiments, ^Ir. Meehean believes that in the 

 Gulf States at least it may be necessary to choose between heavily fer- 

 tilized jionds which w^ill carry a large number of bass to 2 or 2i^ 

 inches and ponds producing an adequate supply of forage food for a 

 longer growing season. In the heavily fertilized ponds the number 

 of fish may run very high if the ponds are drained and the fish re- 

 mo\('d l)y the 1st of June. These ponds could be utilized during the 

 remainder of the season for sunfish and catfish or other species that 

 require a longer growing season and spawn later. The other alterna- 



