596 
BUIvIvETIN of thf bureau of fisheries. 
in the upper strata, say, in the upper 20 or 30 meters of the deeper lakes and in the upper 
10 or 15 meters of the shallower ones. There was one marked exception to this. In 
Canadice Lake the maximum number was found at a depth of 20 meters, within 4 meters 
of the bottom. In Conesus and Otisco Lakes the distribution was similar to that which 
has been found in some of the Wisconsin lakes. That is, the maximum number was 
found in the thermocline, where there was only a small amount of dissolved oxygen. 
For example, there were 123 individuals per liter at a depth of 10 meters in Conesus 
Lake where the oxygen amounted to only o.ii cc. per liter of water. 
The cladoceran population of Seneca Lake was characterized by the absence of 
Daphnia and by the relative abundance of Bosmina. The latter occupied the upper 
50 meters of water and the largest number, 31 individuals per liter, was found at a 
depth of 5 meters in an evening catch. The only other Cladocera represented in the 
plankton catches of Seneca Lake were Ceriodaphnia and Polyphemus pediculus, but 
only a very small number of each was found. Daphnia was absent from the regular 
plankton hauls on Cayuga Lake, but a few specimens of D. hyalina were found in one 
of the townet catches. Bosmina was found at all depths in Cayuga Lake, but it was 
most abundant in the upper 30 meters. The maximum number, 66 individuals per 
liter of water, was obtained in a morning catch at a depth of 10 meters. Ceriodaphnia 
and Polyphemus pediculus were also represented in the plankton of Cayuga Lake, but 
they were not noted in any other lakes. 
Daphnia longispina var. hyalina was represented in all of the lakes except Seneca. 
It was confined chiefly to the epilimnion of the various lakes and was most abundant in 
Hemlock Lake. Daphnia pulex was present in Canadice and Conesus Lakes. It was 
scarce in the former but a little more abundant than D. hyalina in the latter. 
A few Daphnia retrocurva were found in the 12-meter catch of Hemlock Lake. 
Diaphanosoma was noted in Canadice, Canandaigua, Hemlock, Otisco, Owasco, 
and Skaneateles Lakes, and was confined to the epilimnion. It was most abundant in 
Canandaigua Lake, where it averaged about three individuals per liter in the upper 
15 meters. 
Bosmina was obtained in all of the lakes except Canadice, Conesus, and Otisco. It 
was most abundant in Cayuga Lake and Seneca came next. Only a relatively small 
number was obtained in the other five lakes. 
A few specimens of Leptodora hyalina were found in each of the lakes except Conesus 
and Seneca. 
Specimens of Mysis relicia were taken with townets in the lower water of Canandaigua, 
Cayuga, Keuka, and Seneca Lakes. 
