110 Conservation Department 



Classification of Data. — Their interlinkage and interdepend- 

 ence have made it impractical to draw a sharp line of separation 

 or classification of the waters for purpose of discussion, though in 

 the tabulation such division has been more rigorously adhered to. 

 Thus all of Lake Erie data have been incorporated into Series I, 

 all of Niagara river data into Series II, while all other streams 

 with the exception of Cattaraugus creek have been placed in Series 

 III. A separate series (IV) has been devoted to Cattaraugus 

 because of its past importance, and because of the more intensive 

 and collaborative studies made thereon. 



Lake Erie Studies. — In contemplating how the investigation 

 of the lake waters could most intelligently and fruitfully be con- 

 ducted it seemed probable that the effects of shore washings, 

 sewers and tributary streams would be limited to a comparatively 

 narrow stretch of shore waters, and here only would pollution be 

 a factor, since in so far as fish life is concerned contributions to 

 the main lake body as from passing boats would be infinitesimal 

 and negligible. Such a zone is indicated when streams have been 

 roiled and swollen by rains which have not greatly disturbed the 

 smoothness of the lake. But such relatively shallow waters are of 

 paramount importance during the spawning period and early 

 life history of the fish. Hence the question which arises is how far 

 out into the lake do shore factors exert their influence. 



A preliminary cruise was made as far as the New York-Pennsyl- 

 vania State line toward the end of June, samples being taken at 

 pertinent stations, near the surface and bottom at each point and 

 at varying distances from shore. On this and on subsequent 

 cruises the Conservation Department cabin cruiser, Navette, 

 was used as a base, a small boat with outboard motor facilitating 

 the actual collection of samples. As a result of the preliminary 

 findings it was decided to repeat the determinations at monthly 

 intervals, and to take samples at each station approximately 500 

 and 2000 feet from shore. Because of the small likelihood of 

 any sudden changes in the nature of the lake bottom, Mr. N. 

 L. Cutler accompanied only the first and last cruises, dredg- 

 ing sam])les at each station for biological examination and 

 collaboration. 



An additional desideratum was the sampling of the water at 

 intervals between the surface and bottom at Erie's approximately 

 greatest depth, about six miles southeast of Long point, and this 

 was taken care of on the last cruise. The data will be found in 

 Series I of the tables. Dissolved oxygen from a percentage of 

 saturation consideration exhibited but a slight diminution toward 

 the bottom. An interesting thermocline was found between the 

 fifty and seventy-five feet levels, where also the free carbon diox- 

 ide of the lower regions gave place to the fixed carbon dioxide 

 of the upper strata, pll values changing from 7.8 to 8.2. These 

 features are graphically represented in Fig. 1. 



