70 Conservation Department 



covered by the Navette belonging to New York State, and trips 

 were made along both the American and Canadian shores, one 

 trip with the meter nets and another with the Helgoland trawl. 

 Several curious facts with reference to the distribution of the 

 various crustacean species came to light when the results of the 

 Navette hauls were tabulated. There were 14 stations along the 

 American shore from Buffalo to Dunkirk, and 14 along the 

 Canadian shore from Long Point to the Niagara River, the last 

 two in the river itself. In the meter net hauls 2 copepods and 2 

 cladocerans constituted practically the entire bulk of the plankton, 

 with 3 other copepods and 4 cladocerans appearing usually in 

 very small percentages. The copepods were very much in excess 

 of the cladocerans along the Canadian side, except at the two river 

 stations, while the cladocerans were equally predominant on the 

 American side. One of the cladocerans, Dapknia pulex, averaged 

 61 percent of the total bulk of plankton at the 14 American sta- 

 tions, but was wholly lacking at 6 of the Canadian stations. At 

 the two stations in the Niagara river, however, it was present 

 in such numbers as to constitute practically 100 percent of the 

 catch. It is the second in size of the lake cladocerans and the 

 first in abundance of the entire plankton. In chemical composi- 

 tion also it is one of the very best of fish foods, and this rare 

 combination of superiority in size, quantity and quality gives it 

 exceptional value. The other of the two prevailing cladocera, 

 Daphnia retrocurva, was present in varying amounts at all but 

 two of the American stations, but not a single specimen was found 

 along the Canadian shore. A third cladoceran, the curious form 

 known as Leptodora kindtii, was also much more abundant on the 

 American side of the lake. It is the largest cladoceran known 

 and is usually regarded as a surface form, but in this littoral zone 

 it proved to be much more abundant at the bottom during the 

 daytime. In fact at two of the stations near Dunkirk it was 

 present in such numbers in the hauls made with the Helgoland 

 trawl as to constitute practically 100 percent of the total bulk. 



The predominance of the copepods at the Canadian stations, as 

 stated above, is due more to the diminution in numbers and fre- 

 quent absence of the cladocerans than to any marked increase in 

 the copepods themselves. The two prevailing copepods, Diapto- 

 miis siciJis and Episehura, were present at every station on both 

 sides of the lake. The percentages of Diaptoraus averaged larger 

 on the Canadian side, but those of Episehura Avere about even. 

 But a third copepod, Limnocalanus, showed a marked increase on 

 the Canadian side, and as it is the largest copepod in the lake it 

 compensates for the lack of the Daphnias. In the plankton col- 

 lected with the Helgoland trawl there were two copepods and one 

 cladoceran which were not found in the meter net hauls. Three 

 copepods and three cladocerans are largely confined to this zone, 

 one of the copepods, Binptomua sicilis, being very abundant, while 

 the other two and all three cladocerans are quite rare. 



The Inrustric zone: This includes the deeper portions of the 

 lake, which at this eastern end vary from 10 to 62 meters in 



