367 



The production in the lake during this period is greater 

 than that in the river at all times of coincident examination 

 excepting March 14 (.14 and .35). The average production in 

 the lake (.67 cm. 3 ) is 63 per cent, greater than that in the river 

 (.41 cm. 3 ). This percentage of increased production is a meas- 

 ure, or an index, of the impounding or reservoir action of the 

 lake under the hydrographic conditions of these months. The 

 immediate result of the access of Quiver Lake waters to the 

 channel will be a rise in its plankton content from .41 cm. 3 per 

 m. 3 to .414 — an increase of 1 per cent. 



The summary of the interrelations of production in this 

 lake and the river will be made in conjunction with that of Dog- 

 fish Lake, which is only an arm of Quiver Lake. 



DOGFISH LAKE. 



(Table VI.; PI. XVIII., XXX., XXXII.) 



ENVIRONMENTAL CONDITIONS. 



This so-called lake is only the westerm arm of Quiver Lake 

 (PI. II.), separated from the eastern by Quiver Point, a low 

 marshy spit covered with rushes and willows and lying but a 

 few feet above low-water mark. It is of elliptical form, about 

 three quarters of a mile long and one third of a mile wide, 

 contains about 150 acres at low water, and as levels rise it ex- 

 tends northward and eastward over the low bottoms towards 

 Mud Lake and Cartwright Slough, but it is only at highest 

 levels that very much of a current makes its way down through 

 this lake. As levels rise above 8 ft. the intervening ridge sep- 

 arating this lake from the river is gradually submerged, and 

 channel waters invade more or less of the lake. It affords the 

 natural channel for the run-off of the backwaters impounded 

 in several square miles of bottom-land marsh and forest 

 through the swale (PI. II.) which extends towards Mud Lake. 



Its shores are everywhere low and marshy, of black alluvi- 

 um, and a soft black ooze of similar origin covers the bottom of 

 the entire lake. In only a limited area towards the east- 



