20(3 



Conservation Department 



watercress was second with 12.8 grams; pondweed* third, 5.85 

 grams, while willow roots, water buttercup, sago pondweed and 

 water moss produced, less each respectively down to horned pond- 

 weed which gave the least, 2.93 grams per one square foot. 



Considering next, the potential fish foods available over all 

 types of plant beds, Table 9 shows the relative abundance of each 

 class of food. In a total of 7,505 organisms collected, crayfish 

 and shrimps constituted the highest percentage, 40.95%. Most of 

 these were Caledonia shrimps (Gammarus limnaeus), other crusta- 

 ceans being comparatively rare. 



If a comparison is made of the average weight in grams of 

 potential food found per unit area of one square foot as taken in 

 pool bottoms, stream bottoms and plant beds, it is seen that 



Table 9. 



Available Fish Foods by Number and Per Cent Collected in 

 Submerged Plant Beds * 



Order 



Number Per cent 



Crayfish and shrimps (Crustacea) 



Flies (Diptera) 



Bugs (Hemiptera) 



Caddisflies (Trichoptera) 



Beetles (Coleoptera) 



Mayflies (Ephemerida) 



•Stoneflies (Plecoptera) 



Snails and clams (Mollusca) 



Sialis larvae et al. (Neuroptera) . . 



Dragonflies (Odonata) 



Miscellaneous 



Totals 



3,073 



40.95 



1,618 



21.56 



710 



9.46 



710 



9.46 



567 



7.55 



416 



5.54 



83 



1.11 



64 



.85 



11 



.15 



1 



.01 



252 



3.37 



7,505 



100.01 



* This table includes the bottom fauna in all square feet studied as well as the 

 animals on or about the plants. 



the plant beds were by far the most productive, giving an average 

 of 9.16 grams against .26 grams for pools and 1.21 grams for 

 streams. From these figures plant beds plus the bottom foods 

 beneath, are 35.2+ times as rich in food as pool bottoms, and 7.5 + 

 times richer than stream bottoms, As stated elsewhere, stream 

 bottoms were found to be 4.6 times richer in potential food than 

 pool bottoms per unit area. Thus it is seen that great increase 

 in potential food is found in bottoms in which various types of 

 aquatic vegetation have developed. The reason for greater pro- 

 ductivity in plant beds, aside from the fact that they are largely 

 responsible for the oxygenation of the water, must be due to the 

 fact that they furnish more food and shelter for aquatic organisms 

 than do merely bare pool or stream bottoms. 



* Long-leaved pondweed. 



