The investigation took into special consideration the influence upon the two-year-old 

 carp, that were present in the pond, by measuring the productivity of aquatic organisms 

 when the numbers stocked were varied. 



The total amount as to number and weight of carp, of existing Chiron omidae larvae, at 

 different times during the summer, upon a given area is the i-esult of fluctuating gain and 

 loss, chiefly due to the following causes: 



1. Gain 



(a) Numerical increase through influx. 



(b) IVeight increase through growth of larvae. 



II. Loss (numerically and by wej^ht) 



(a) Through pupation of larvae, metamorphosis into flying 

 insects and death. 



(b) Through consumption by fish and other aquatics. 



Figure 6 shall give an illustration to the points under discussion. 



3M ?IW m SS SM 9W 3JS t)X 



Fi{j. 6. iluTiber and total weight in mg. of Chironomidae larvae per 



200 squ£Lre centimeter bottoi.i surface, in four differently planted (as to 

 nui±ier of ixsh) experiaental ponds during one summer's season, 

 rond 3: ^orr.El stockinf; v.dth tvro-year-old carp. 

 Pond 4: rour times above normal. 

 Pond 5: Eight times above normal. 

 Pond 6: Sixteen ti:3es above normal. 

 ■,Ve see at a glance that in all four ponds, freshly flooded in April, the number of 

 aquatics is still very small, three days after the flooding. Three weeks later, this number 

 has hardly been tripled, although the ponds were still not stocked. This increase in number 

 and weight — quite apparent since a decrease is hardly possible — is naturally prompted 

 through influx and the favorable conditions of existence. 



On April 22, the ponds were planted (stocked) v.lth two-year-old carp of an average 

 weight of 265 grams, and an excessive increase in number and weight is still at hand. 



37 



