361 



1897. 



(Tables V., XIII.; PI. XXVIII., XLVIII.) 



There are 24 collections in this year, with an average of 

 0.88 cm. 3 per m. 3 as compared with 3.69 in the river, and a max- 

 imum of 13.38 on April 27 — more than twofold the production 

 in the river (5.1 1) on that day. 



The collections of the first six months of this year are so 

 infrequent that the course of production is but slightly indicat- 

 ed. In February the production in the impounded waters of the 

 winter flood in Quiver Lake (.19) is nearly fivefold that in the 

 current-swept channel ( .04) , while in March there is little differ- 

 ence (.34 and .38) in their plankton content. The collection of 

 April 27 probably falls near the presumably common vernal max- 

 imum and in the midst of the decline of the spring flood. Since 

 Quiver Lake at the stage of river (11.6 ft.) then prevalent 

 contains the run-off of the impounded backwaters to the north, 

 it is not surprising that its plankton content (13.38) is more 

 than double that of the river (5.11). The similarity in the 

 movement of production thus far seen in this year is interrupted 

 on May 25 by the decline in the lake to 1.29, while the river 

 rises to 5.62. The decline in the lake may be attributed to the 

 great reduction in impounding area due to the decline in levels 

 to 8 ft., and to the gain in proportion in the lake of the contri- 

 butions of creek and spring water and of the area occupied by 

 the now rapidly appearing vegetation. The silt-bearing flood 

 of June in the river yields less (.27) than the lake waters (1.26) 

 impounded by the rise of the river. 



In the last six months of the year the collections are of 

 sufficient frequency to enable us to trace somewhat the move- 

 ment in production. This period is marked by a great depres- 

 sion in plankton content as compared with that of the same 

 season in the previous year, the average for each being 1.06 and 

 .23. The parallelism in the movement of production can still 

 be traced in the slight tendency in Quiver Lake to increased 

 production in July, September, and November at times of pulses 



